( PDF ) A importância da floração seqüencial de Malpighiaceae para a manutenção da diversidade de tripes (Thysanoptera) no cerrado

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UNIVERSIDADE FEDERAL DE UBERLÂNDIA – UFU

INSTITUTO DE BIOLOGIA

PROGRAMA DE PÓS GRADUAÇÃO EM ECOLOGIA E CONSERVAÇÃO

DE RECURSOS NATURAIS

A IMPORTÂNCIA DA FLORAÇÃO SEQÜENCIAL DE

MALPIGHIACEAE PARA A MANUTENÇÃO DA DIVERSIDADE

DE TRIPES (THYSANOPTERA) NO CERRADO

ESTEVÃO ALVES DA SILVA

UBERLÂNDIA – MG

FEVEREIRO, 2010

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ESTEVÃO ALVES DA SILVA

A IMPORTÂNCIA DA FLORAÇÃO SEQÜENCIAL DE

MALPIGHIACEAE PARA A MANUTENÇÃO DA DIVERSIDADE

DE TRIPES (THYSANOPTERA) NO CERRADO

ORIENTADOR

DR. KLEBER DEL-CLARO

CO-ORIENTADORA

DRA. HELENA MAURA TOREZAN SILINGARDI

UBERLÂNDIA

FEVEREIRO - 2010

“Dissertação apresentada à Universidade Federal de

Uberlândia, como parte das exigências para obtenção

do título de Mestre em Ecologia e Conservação de

Recursos Naturais”.

ads:

ESTEVÃO ALVES DA SILVA

A IMPORTÂNCIA DA FLORAÇÃO SEQÜENCIAL DE

MALPIGHIACEAE PARA A MANUTENÇÃO DA DIVERSIDADE

DE TRIPES (THYSANOPTERA) NO CERRADO

APROVADA em 22 de fevereiro de 2010

Prof. Dr. Giuliano Buzá Jacobucci, UFU

Prof. Dra. Marina Farcic Mineo, IFTM

Prof. Dr. Glein Monteiro de Araújo (Suplente), UFU

PROF. DR. KLEBER DEL-CLARO

ORIENTADOR

UFU

CO-ORIENTADORA

PROFª. DRA. HELENA MAURA TOREZAN SILINGARDI

UFU

UBERLÂNDIA

FEVEREIRO - 2010

“Dissertação apresentada à Universidade Federal de

Uberlândia, como parte das exigências para obtenção

do título de Mestre em Ecologia e Conservação de

Recursos Naturais”.

AGRADECIMENTOS

Aos meus pais e familiares e a Deus

Aos meus orientadores Dr. Kleber Del Claro e Drª. Helena Maura Torezan Silingardi pelo

apoio e confiança nestes dois últimos anos

Agradeço também:

· Universidade Federal de Uberlândia e Programa de Pós Graduação em Ecologia e

Conservação de Recursos Naturas, UFU

· À secretária do PPGECRN Maria Angélica pela sua solicitude e amabilidade

· Instituto de Biologia, UFU

· Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

· Aos Profs. Giuliano Buzá Jacobucci, Marina Farcic Mineo e Glein Monteiro de

Araújo por participarem da banca

· Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

· Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)

· Dr. Laurence Mound, Australia's Commonwealth Scientific and Industrial Research

Organisation (CSIRO)

· Prof. Rafael Ariza, Faculdade de Engenharia Mecânica, UFU

· Doutorando Adriano Cavalleri, Universidade Federal do Rio Grande do Sul

· Corpo Docente do Programa de Pós Graduação em Ecologia e Conservação de

Recursos Naturas, UFU, em especial aos professores Drª. Cecília Lomônaco, Drª.

Tatiana Cornelissen e Dr. Heraldo Vasconcelos pelas aulas de estatística.

· A todo o Laboratório de Ecologia Comportamental e Interações, UFU (LECI) em

especial aos doutorandos Everton Tizo Pedroso, Jonas Byk e Denise Lange; e às

mestrandas Alexandra Bachtold, Ceres Belchior, Andréa Andrade Vilela e Fernanda

Alves Martins.

· Corpo de funcionários do Instituto de Biologia, UFU, bem como diretórios da

universidade como a garagem e a gráfica

· Ao Sr. Nilson Dias de Oliveira, presidente do Clube de Caça e Pesca Itororó de

Uberlândia, por ceder gentilmente a área de reserva natural em que este estudo foi

conduzido

· À minha turma de mestrado

Agradeço aos meus amigos, conhecidos e também àqueles que seguem o lema de “se não

ajudar, atrapalhe, afinal o importante é participar”. Provavelmente devo ter esquecido de

alguém.

Aelton Giroldo

Amanda Ferreira e Cunha

Camila Bonizário

Danielle Justino

Diego Oliveira

Eurípedes Luciano Silva Júnior

Felipe Wanderley

Franco Costa Gondim

Guilherme Mitsuo Yugue

Lorrayna Guedes

Luciana Nascimento Custódio

Marcela Yamamoto

Patricia Tieme Fujimura

Pietro Kiyoshi Maruyama Mendonça

Rafaella Librelon

Tayná Lopes Pires

Tiago Luiz Massochini Frizzo

ÍNDICE

CAPITULOS DE REVISÃO.............................................................................................

1. TRIPES (THYSANOPTERA: INSECTA).................................................................. 1

1.1 Características gerais................................................................................................... 1

1.2 Morfologia de Tripes................................................................................................... 3

1.2.1 Morfologia externa.................................................................................................... 3

1.2.2 Anatomia interna...................................................................................................... 4

1.3 Interações ecológicas.................................................................................................... 5

1.3 Referências Bibliográficas........................................................................................... 9

2. MALPIGHIACEAE (MALPIGHIALES)................................................................... 13

2.1 Características gerais.................................................................................................. 13

2.2 Espécies abordadas no estudo.................................................................................... 14

2.3 Estudos em ecologia com Malpighiaceae................................................................... 16

2.4. Referências Bibliográficas.......................................................................................... 19

CAPÍTULO ÚNICO: The importance of Malpighiaceae sequential flowering to the

maintenance of thrips diversity in Brazilian Savanna

1 INTRODUÇÃO...............................................................................................................

2 CONCLUSÃO................................................................................................................. 23

3 INTRODUCTION……………………………………………………………………... 24

4 MATERIAL AND METHODS………………………………………………………..

4.1 Study area………………………………………………………………………... 26

4.2 Preliminary observations……………………………………………………….. 27

4.3 Data collecting…………………………………………………………………… 27

4.4 Thysanopterofauna descriptions……………………………………………….. 28

4.5 Flower size and the abundance of thrips………………………………………

4.6 Environmental data……………………………………………………………... 30

4.7 Plant phenology………………………………………………………………….. 30

4.8 Testing the occurrence of seasonality………………………………………….. 31

5 RESULTS........................................................................................................................ 31

6 DISCUSSION.................................................................................................................. 41

6.1 Thrips occurrence and its importance: a brief review………………………... 41

6.1.1 Suborder Terebrantia…………………………………………………………. 41

6.1.2 Sub Order Tubulifera, family Phlaeothripidae……………………………… 46

6.2 Thrips community and host plant preferences…………………………………

6.3 Resource and predators…………………………………………………………. 50

6.4 Polyphagy………………………………………………………………………… 52

6.5 Seasonality and phenology……………………………………………………… 53

6.6 The importance of sequential flowering and major hosts…………………….. 54

7 CONCLUSION................................................................................................................

8 REFERENCES................................................................................................................ 57

Dados Internacionais de Catalogação na Publicação (CIP)

S586i

Silva, Estevão Alves da, 1982-

A importância da floração seqüencial de Malpighiaceae para a ma-

nutenção da diversidade de tripes (Thysasanoptera) no cerrado [manus-

crito] Estevão Alves da Silva. - 2010.

70 f. : il.

Orientador: Kleber Del-Claro.

Co-orientadora: Helena Maura Torezan Silingard.

Dissertação (mestrado) - Universidade Federal de

Uberlândia, Progra-

ma de Pós-Graduação em Ecologia e Conservação de Recursos

Naturais.

Inclui bibliografia.

Relação inseto-planta. 2. Ecologia do cerrado - Teses. I. Del-Claro,

Kleber. II. Silingard, Helena Maura Torezan. III. Universidade Federal de

Uberlândia. Programa de Pós-Graduação em Ecologia e Conservação de

Recursos Naturais.

CDU:

595.7-155.7

Elaborado pelo Sistema de Bibliotecas da UFU / Setor de Catalogação e Classificação

RESUMO

Alves-Silva, E. A importância da floração seqüencial de Malpighiaceae para a

manutenção da diversidade de tripes (Thysasanoptera) no cerrado. 2010. 70f.

Dissertação (Mestrado em Ecologia e Conservação de Recursos Naturais) – Universidade

Federal de Uberlândia, Uberlândia, 2010.

Para se entender o papel de cada planta na ecologia de tripes, dois principais critérios

precisam ser quantificados: a regularidade temporal em que os indivíduos são encontrados em

uma planta e sua abundância em uma determinada planta relativamente a outras. A escolha de

plantas representativas pode fornecer informações que permitam definir padrões temporais de

ocorrência e avaliar a importância de fatores ambientais na comunidade destes insetos. Neste

contexto, plantas que apresentem floração seqüencial podem prover elementos a respeito da

importância de cada hospedeiro em abrigar populações de tripes ao longo do ano. Este estudo

teve o objetivo de testar a hipótese de que malpighiáceas com floração seqüencial são

responsáveis pela manutenção de tripes no decorrer do ano, assumindo a premissa que tripes

migram de planta em planta de acordo com a fenologia de floração. O estudo foi realizado em

uma área de Cerrado sentido restrito em Uberlândia, Minas Gerais, Brasil. As plantas

estudadas foram Banisteriopsis malifolia, B. campestris, B. laevifolia, Byrsonima intermedia

e Peixotoa tomentosa. As coletas foram realizadas de março de 2008 a fevereiro de 2009.

Foram encontradas 19 espécies de tripes distribuídas em oito gêneros e três famílias

Phlaeothripidae, Thripidae e Heterothripidae, perfazendo 3788 (5.61±6.49,

±1SD)

indivíduos nas 675 flores analisadas. Testes de fenologia mostraram que todas as cinco

malpighiáceas apresentaram floração seqüencial, o que permitiu aos tripes migrarem entre as

plantas e encontrarem alimento e abrigo o ano todo. A planta com maior abundância de tripes

foi P. tomentosa, seguida por B. laevifolia, no entanto, a diversidade foi maior em B. malifolia.

As únicas espécies de tripes presentes em todas as plantas e passíveis de migrar dependendo

da fenologia de floração foram Frankliniella condei, Scutothrips nudus, Frankliniella sp. 1. e

Heterothrips peixotoa. A riqueza e diversidade encontradas nas malpighiáceas são umas das

maiores já registradas para a ocorrência de tripes em plantas relacionadas taxonomicamente e

isso se deve ao aspecto conservativo das flores que fornecem tanto alimento quanto proteção

contra predadores. Este estudo mostra que malpighiáceas com floração seqüencial têm um

importante papel na manutenção da diversidade de tripes, atuando como um recurso natural

que auxilia na sobrevivência e diversificação destes insetos no cerrado brasileiro.

Palavras-chave: Heterothrips peixotoa, Frankliniella, plantas hospedeiras, fenologia

ABSTRACT

Alves-Silva, E. The importance of sequential flowering Malpighiaceae to the

maintenance of thrips (Thysanoptera) in Brazilian Savanna. 2010. 70f. Dissertação

(Mestrado em Ecologia e Conservação de Recursos Naturais) – Universidade Federal de

Uberlândia, Uberlândia, 2010.

To understand the role of each plant species in the ecology of thrips, two principal criteria

need to be quantified: the regularity with which individuals are found on a plant species over

time, and their abundance on that particular plant species relative to other ones. The choice of

representative plants may supply subsidies to define temporary patterns and to evaluate the

importance of environmental factors on the community of these insects. In this context

sequential flowering plants can provide insightful information about the importance of each

host in supporting thrips populations along the year. This study aimed to test the hypothesis

that Malpighiaceae sequential flowering is responsible for the maintenance of thrips

throughout the year, assuming the premise that thrips migrate from different plants according

to the flowering phenology. Fieldwork was carried out from March 2007 to February 2009 at

a strictu sensu Cerrado area in Uberlândia, Minas Gerais State, Brazil. The plants studied

comprised Banisteriopsis malifolia, B. campestris, B. laevifolia, Byrsonima intermedia, and

Peixotoa tomentosa. We found a total of 19 species of thrips in eight genera distributed in the

three families Phlaeothripidae, Thripidae and Heterothripidae. Phenological analysis showed

that the five Malpighiaceae species studied presented sequential flowering, enabling thrips to

migrate from plants and to find food and shelter along the year. The plant which presented

more thrips was P. tomentosa, followed by B. laevifolia whereas the diversity was higher in B.

malifolia. The only thrips species present in all plants and likely to migrate from hosts

according flowering phenology were Frankliniella condei, Scutothrips nudus, Frankliniella

sp. 1 and Heterothrips peixotoa. The richness and diversity recorded are the highest ever

sampled for thrips occurrence in a group of related taxonomic plants, because the

conservative aspect of Malpighiaceae flowers provide food resources and protection against

predators. This study showed that sequential flowering Malpighiaceae plays an important role

in the maintenance of thrips diversity, being an important natural resource to help in the

survivorship and diversification of these insects in Brazilian Savanna.

Key words: Heterothrips peixotoa, Frankliniella, host plants, phenology

CAPÍTULOS DE REVISÃO

1. TRIPES (THYSANOPTERA: INSECTA)

1.1 CARACTERÍSTICAS GERAIS

Tripes são insetos fitófagos, micófagos ou predadores que ocupam uma vasta gama de

habitats, ocorrendo nas regiões tropicais, subtropicais e temperadas (Ananthakrishnan 1993).

Sua diversidade adaptativa lhes permitiu a exploração de diversos nichos como flores,

serapilheira e cascas de árvores (Richards & Davies 1988).

A ordem Thysanoptera evoluiu presumivelmente de ancestrais que se alimentavam de

fungos e detritos, um hábito que foi retido nos membros da família Merothripidae e também

pela ordem Psocoptera, que provavelmente dividiu um ancestral comum com tripes (Mound

& Marullo 1996). Tripes podem ter agido como polinizadores durante a radiação das

fanerógamas e este comportamento foi mantido para algumas espécies (Momose et al. 1998,

Sakai 2001). Subseqüentemente, três formas majoritárias de alimentação foram adotadas –

hifas e esporos de fungos, folhas e flores, além de néctar, tecidos florais, o conteúdo das

células de folhas jovens; e o fluido corporal de pequenos artrópodes (Mound 2002a, Morse &

Hoddle 2006).

Atualmente são reconhecidas duas subordens de tripes, Tubulifera e Terebrantia (Grimaldi

& Engel 2005). As diferenças mais conspícuas destas duas subordens estão no ovipositor e no

formato das asas. As fêmeas dos Terebrantia têm um ovipositor em forma de serra, visível

ventralmente nos últimos segmentos abdominais, enquanto que nos Tubulifera, o abdome de

ambos os sexos é tubular no ápice, não havendo ovipositor visível (Mound & Marullo 1996)

(FIGURA 1). Quanto às asas, nos Terebrantia, o primeiro par possui venações que podem ser

acompanhadas de cerdas. Já nos Tubulifera, as asas não dispõem de venações. Mais de 95%

das espécies de Terebrantia estão associadas a plantas enquanto que 60% dos Tubulifera são

fungívoros (Mound 2005). O sistema de acasalamento em Thysanoptera é complexo e pode

envolver ferormônios, atrativos visuais, sons ou uma combinação destes. A corte é feita pelo

macho que usa suas antenas para fazer contato com a fêmea e deixá-la imóvel para que a

cópula ocorra (Milne et al. 2007).

O ciclo de vida dos tripes é intermediário entre holometábolo e hemimetábolo. Os estágios

imaturos são chamados de larvas e todas as espécies de tripes possuem mais de um estágio de

pupa (Mound & Marullo 1996). (FIGURA 2). A maioria das espécies completa seu ciclo de

ovo a adulto em duas ou três semanas. A duração varia de acordo com o hospedeiro e com

fatores abióticos como temperatura, umidade e fotoperíodo (Ananthakrishnan 1993,

Whittaker & Kirk 2004).

A B

FIGURA 1. Diferenças morfológicas das duas subordens de tripes, evidenciadas pelo ovipositor que na (A)

subordem Tubulifera o ovipositor tem a foram cônica e está presente nos últimos segmentos abdominais e na (B)

subordem Terebrantia é serreado e localizado ventralmente (FIGURA: Frantz et al. (2010)).

As larvas das espécies que habitam flores empupam no solo enquanto que nas espécies

que se alimentam de fungos, as pupas são encontradas em associação com adultos e larvas, o

que pode ter sido importante para o desenvolvimento da socialidade em algumas espécies

(Crespi et al. 1997). Crespi (1988) descreve o comportamento de Hoplothrips karnyi (Hood),

uma espécie que se alimenta de fungos, onde o macho defende um território com massa de

ovos e acasala com fêmeas que eventualmente aparecem para ovipor. As lutas com outros

machos por território levam freqüentemente a morte de um deles, sendo que os indivíduos

menores são os mais injuriados após as lutas. Este comportamento de guarda envolve danos

físicos devido às lutas e um custo energético substancial, que deve ser compensado por um

aumento no valor adaptativo do indivíduo ao acasalar com mais fêmeas.

Adultos e larvas de ambas as subordens compartilham um único atributo estrutural:

somente a mandíbula esquerda é desenvolvida, a direita é reabsorvida no estágio embrionário

(Mound 2005). Apesar dos diversos hábitos alimentares, os estiletes dos tripes são

marcadamente uniformes em estrutura. A mandíbula única é usada para criar um buraco no

alimento, como em grãos de pólen ou células de folhas e flores. Os estiletes maxilares são

pares e estão ligados para formar um canal alimentar único, que se insere na fonte alimentar.

Assim, os conteúdos de cada célula da folha, flor ou grão de pólen são sugados (Mound &

Marullo 1996) (FIGURA 3). Cerca de 700 espécies de tripes são conhecidas no Brasil,

compreendendo 10% da fauna mundial (Monteiro 2002, Mound 2002b). Um terço destas

espécies são agrupadas na subordem Terebrantia e dois terços na Tubulifera (Monteiro 2002).

No país, Thripidae (Terebrantia) e Phlaeothripidae (Tubulifera) são as famílias mais

representativas, com 27% e 66,5%, respectivamente. As outras quatro famílias,

Uzelothripidae (0,2%), Merothripidae (1,8%), Aelothripidae (1,5%) e Heterothripidae (3%)

são pouco conhecidas. Devido à ênfase que é dada à agricultura, os registros de tripes são

mais extensos para espécies que são pragas associadas à plantações, como Frankliniella e

Thrips (Nagata et al. 1999, Monteiro et al. 2001).

Adulto

Ovo

Larva de

1º ínstar

Larva de

2º ínstar

Prepupa

Pupa

Solo

FIGURA 2. Esquema do ciclo de vida de tripes. As fases larvais são acompanhadas das fases de pupa que se

enterram no solo para completar seu desenvolvimento ao estágio adulto. (FIGURA: Hoodle (2010)).

Folha

Cabeça de um tripes

FIGURA 3. Diagrama da alimentação de tripes, onde a mandíbula perfura o tecido foliar para sugar seu conteúdo.

(Figura: Costa Lima 1936).

1.2 MORFOLOGIA DE TRIPES

1.2.1 Morfologia externa – a cabeça é levemente quadrangular, de forma que um par de

pequenos, porém proeminentes olhos compostos com largas facetas são vistos superiormente.

Três ocelos estão presentes nas formas aladas e ausentes nas formas ápteras. As antenas

possuem de seis a 10 segmentos e sua inserção ocupa uma posição frontal na cabeça. O corpo

possui cerdas que são taxonomicamente importantes. As partes bucais são adaptadas para

perfurar e sugar o alimento. As asas são membranosas, estreitas, possuem franjas nas bordas e

podem ou não ter venações. O abdômen é longo e composto por 11 segmentos (FIGURA 4).

Os machos possuem um edeago eversível (Ross 1965, Richards & Davies 1988, Mound &

Marullo 1996, Grimaldi & Engel 2005).

1.2.2 Anatomia interna – o sistema digestório é caracterizado por um mecanismo de bomba

de sucção provida de músculos radiais, um longo esôfago, um extenso intestino e quatro

túbulos de Malpighi. Dois ou três pares de glândulas salivares estão localizadas no tórax e

abdome e seus ductos se unem para formar um canal comum que se abre em frente ao esôfago.

O intestino médio forma a maior porção do tubo alimentar e é dividido em uma câmara

anterior seguida de uma região posterior circular. O final do intestino forma uma passagem

direta para o ânus e possui quatro papilas retais.

FIGURA 6. (A) Tripes adulto, as asas franjadas e a disposição das cerdas ao longo do corpo e das (B) antenas

são usadas para a identificação das espécies. (Figura: Costa Lima 1936).

Quanto ao sistema nervoso, o cérebro é bem desenvolvido, o gânglio subesofageano e o

protorácico são fundidos enquanto que os gânglios meso e metatorácicos são separados. O

sistema circulatório consiste de uma pequena bomba contrátil no oitavo segmento abdominal.

Nas fêmeas, os ovários contêm quatro pequenos ovaríolos panoísticos, uma pequena

espermateca pigmentada e uma glândula em forma de saco. Nos machos, um par de testículos

fusiformes se comunicam ao vaso deferente e ao ducto ejaculatório. O sistema traqueal é bem

desenvolvido e se abre ao exterior por meio de quatro pares de espiráculos, localizados no

meso e metatórax e no primeiro e oitavo segmentos abdominais (Richards & Davies 1988).

1.3 INTERAÇÕES ECOLÓGICAS

A gama de plantas em que tripes podem ser encontrados é considerável. Inclui algumas

briófitas, pteridófitas e gimnospermas, bem como as folhas e flores de muitas angiospermas,

particularmente aquelas que ofereçam locais para abrigo, reprodução e permitam a

manutenção do inseto (Mound & Terry 2001). Muitas espécies de tripes que vivem em flores

se alimentam de pólen. Seria fácil pensar em tal associação como mera predação de tripes nas

plantas, porém adultos podem ser observados freqüentemente carregando pólen em seus

corpos e voando ativamente entre flores (Terry 2002). Não há dúvida de que tripes conduzem

pólen entre plantas, mas a demonstração da significância destes pequenos insetos na

polinização raramente tem sido estudada.

Apesar das queixas de Charles Darwin de que tripes interferiam em seus experimentos de

polinização, sabe-se hoje que estes insetos podem atuar como polinizadores principais ou

secundários de várias espécies de plantas (Mound 2005). Sakai (2001) estudando a evolução

de sistemas de polinização demonstrou que tripes têm relações mutualísticas com Castilla

elastica Sessé ex. Cerv., na qual a planta provê alimentação para o inseto e este promove

polinização cruzada. Momose et al. (1998) também observaram que em, Popowia pisocarpa

(Blume) somente pequenos insetos como tripes conseguiam entrar na câmara floral reduzida e

promover polinização, assim como Mound & Terry (2001) demonstraram para Macrozamia

macdonnellii (F. Muell. ex Miq.) F. Muell. ex A. DC. Similarmente, Hagerup & Hagerup

(1953), Eisikowitch & Woodell (1975), Thien (1980), Bawa et al. (1985), Moog et al. (2002)

entre outros, descrevem sistemas em que tripes são polinizadores. As adaptações de tripes

como polinizadores envolvem aspectos tais como a disponibilidade de pólen ou néctar como

fonte alimentar e um microclima dentro do tubo da corola no qual tripes podem se reproduzir

(Ananthakrishnan 1993). Estas interações envolvem múltiplas recompensas: alimento, local

protegido para atividades reprodutivas, substrato para oviposição; todos fornecidos por

estruturas florais (Pellmyr & Thien 1986, Armstrong & Marsh 1997, Momose et al. 1998,

Sakai 2001).

Esta característica mais nobre de tripes, entretanto, não os demove de seu status mais

conhecido. Algumas espécies são reconhecidamente pragas em vários agroecossistemas

economicamente importantes (Morse & Hoddle 2006, Dreistadt et al. 2007). No Brasil,

Frankliniella juntamente com Thrips, são os gêneros de Thysanoptera que reúnem o maior

número de espécies-praga, seja pelos danos diretos causados aos tecidos vegetais durante a

alimentação e/ou pela transmissão de agentes fitopatogênicos, especialmente Tospovirus, que

acarretam grandes perdas econômicas na agricultura (Nagata & Avila 1999). Os hábitos

alimentares das larvas são similares aos dos adultos, porém, somente as larvas adquirem o

vírus se alimentando de plantas previamente infectadas (Mound & Marullo 1996). O vírus se

desenvolve no inseto e este quando adulto, inocula o vírus nas plantas em que se alimenta, via

saliva. A infecção de vírus nas plantas é ruim para os tripes, pois isso diminui a sobrevivência

das larvas das gerações subsequentes e consequentemente afeta o fitness da população

(Belliure et al. 2005).

Além de polinização e herbivoria, tripes exibem outras interações ecológicas como

predação (Agrawal et al. 1999), características como mimetismo (Mound & Reynaud 2005) e

formação de galhas (McLeish et al. 2007) (FIGURA 5). Os tripes que formam galhas são

espécie-específicos (Mound & Marullo 1996) e preferem plantas com tecidos jovens, os quais

são alterados celular e metabolicamente após a colonização, em tecidos com elementos

nutritivos que servem de base alimentar, permitindo a uma população de tripes alcançar até 12

gerações por ano (Ananthakrishnan 1993).

Não há um consenso a respeito de quais mecanismos ou elementos são responsáveis pela

atração de tripes para um hospedeiro específico. Mound (2005) afirma que tripes não são

encontrados associados a flores de morfologia aberta que atraem abelhas e moscas, nem com

aquelas com grandes quantidades de néctar, no entanto, Kirk (1997) relata que algumas

espécies de tripes são encontradas somente em flores pequenas, brancas e com um forte odor,

mesmo quando estão abertas. No Cerrado, tripes podem ser encontrados sob tipos variados de

flores (dados não publicados.) que se encaixariam perfeitamente em ambas as proposições

defendidas pelos autores acima. Considerando-se a literatura presente sobre tripes, convém

considerar que estes insetos são atraídos pelo odor liberado de flores (Momose et al. 1998),

mas também podem ocorrer fatores conjuntos de atração (Milne & Walter 2000, Sakai 2001),

como acontece com alguns besouros (Gottsberger & Silberbauergottsberger 1991). Poucos

autores fornecem listas com informações de tripes e suas plantas hospedeiras e possíveis

interações com outros insetos que também possam utilizar a mesma planta. Del-Claro et al.

(1997), estudando Peixotoa tomentosa A. Juss verificaram que a espécie de tripes presente,

Heterothrips peixotoa Del-Claro, Marullo & Mound, 1997, provocava danos nas flores pela

herbivoria. Porém estes tripes conseguiam escapar de predadores se escondendo nas câmaras

formadas entre a pétala e a sépala destas flores. Apesar desta interação não ser benéfica para a

planta, os tripes obtém alimento, local protegido para atividades reprodutivas e substrato para

oviposição, todos fornecidos pelas estruturas florais (Pellmyr & Thien 1986, Armstrong &

Marsh 1997).

FIGURA 5. Diversidade de interações e comportamento de tripes. (A) Indivíduo de Franklinothrips

vespiformis (DL Crawford, 1909) adulto que mimetiza formigas; (B) larva de F. vespiformis se

alimentando de outro tripes; (C) Cicadófita polinizada por tripes na Austrália; (D) larva de

Aulacothrips dictyotus Hood fixada na porção ventral do membracídeo Enchenopa

brasiliensis Strümpel, realizando ectoparastismo; (E) Dano foliar provocado em Morinda citrifolia L.

(Rubiaceae) pela espécie de tripes Heliothrips haemorrhoidalis (Bouché, 1833); (F) Folha de amendoim

(Arachis hypogaea L. (Fabaceae)) apresentando anéis concêntricos causados por vírus (Tomato spotted wilt virus

(TSWV)) transmitidos por tripes. (FIGURAS A e B: www.entocare.nl/nl/eigen%20producten/predatrip.htm; C:

www. bugwise.net.au/invertebrates/pollination; D: Estevão Alves da Silva; E: www.ctahr.

hawaii.edu/noni/thrips.asp. F: www.lookfordiagnosis.com/mesh_info. php?term= Tospovirus&lang=3).

Além de ser o primeiro estudo que abordava ecologia de interações de tripes no Cerrado,

este estudo também teve o mérito de descrever uma nova espécie de tripes. Pouco tempo

depois, um novo gênero de tripes, Nexothrips, espécie N. delclaroi, foi encontrado em flores

de Hortia sp., também no Cerrado (Marullo & Mound 2000). Mais recentemente, uma

interessante e notável interação ecológica foi registrada no cerrado. Indivíduos imaturos da

espécie de tripes Aulacothrips dictyotus Hood foram registrados como sendo ectoparasitas de

Enchenopa brasiliensis Strümpel (Membracidae) enquanto que os tripes adultos utilizavam os

membracídeos para forese (Alves-Silva & Del-Claro dados não publicados). Das mais de

6000 espécies de tripes conhecidas, somente A. dictyotus apresenta hábito ectoparasítico

enquanto que as outras espécies são em sua maioria fitófagas ou fungívoras (Mound & Morris

2007). Exceto por estes trabalhos, para o Cerrado existem poucas informações sobre tripes,

suas plantas hospedeiras, interações ecológicas com outros insetos e caracterização das

populações destes insetos ao longo do ano.

Talvez o estudo mais extenso e conclusivo já realizado com populações de tripes seja o de

Davidson & Andrewartha (1948). Estes autores analisaram a variação na população de Thrips

imaginis Bagnall durante seis anos em rosas na Austrália e concluíram que apesar de a

espécie de tripes ser ativa durante todo o ano, as maiores densidades ocorrem durante a

primavera e o verão, no período de floração das rosas, suas plantas hospedeiras. Entretanto,

atualmente também são considerados que fatores dependentes da densidade influenciam as

populações de tripes (Mound 2005). Os estudos atuais, longe de abrangerem um período tão

extenso, buscam principalmente descrever espécies associadas à agricultura ou ligadas ao

controle biológico (Deligeorgidis et al. 2005).

No Brasil, o estudo mais amplo abordando tripes, suas plantas hospedeiras e a ocupação

de diferentes microhábitats foi realizado por Pinent et al. (2006). Em um inventário

conduzido no sul do Brasil, estes pesquisadores amostraram 73 espécies de tripes,

pertencentes a quatro famílias (Merothripidae, Heterothripidae, Thripidae e Phlaeothripidae),

na qual Frankliniella foi o gênero mais representativo. Este trabalho abrangeu não somente as

flores, mas também ramos e serapilheira, denotando uma grande ocupação de tripes nestes

locais. A diversidade encontrada, no entanto, é pouco representativa para a thysanopterofauna

do Brasil como um todo, devido a falta de amostragens em áreas extensas do país, dada a

diversidade de nossa flora e ecossistemas (Monteiro 2002). Deste modo, nosso conhecimento

sobre tripes e suas plantas hospedeiras é largamente subestimado.

São boas as perspectivas para o estudo de tripes no Brasil e no mundo. Hoje existem

diversas técnicas disponíveis para a identificação (Moritz et al. 2000, Mound & Morris 2007)

e criação de tripes em laboratório (Murai & Loomans 2001), apesar de haver poucos

taxonomistas e ecólogos. No Brasil, particularmente no Cerrado, estudos têm sido conduzidos

desde 1996 pelo Dr. Kleber Del Claro a fim de se identificar tripes e suas plantas hospedeiras,

com um enfoque mais ecológico. Contando desde então com o apoio do Dr. Laurence Mound

(Csiro, Austrália), duas novas espécies de tripes já foram encontradas (Del-Claro et al. 1997,

Marullo & Mound 2000) e devido a alta diversidade florística do Cerrado (Furley 1999), é

bem provável que novas espécies venham a ser descobertas.

As expectativas para os próximos anos prevêem a caracterização das populações de tripes

presentes nas espécies vegetais mais abundantes no Cerrado buscando identificar padrões

sazonais de sua ocorrência. Isto permitirá o estabelecimento de uma linha de pesquisa firme e

duradoura em thysanopterologia em uma fração de um dos mais importantes biomas do país

(Furley & Ratter 1988). A dimensão destes nossos estudos pretende abordar aspectos da

biodiversidade, ecologia e comportamento de tripes.

1.4 REFERÊNCIAS BIBLIOGRÁFICAS

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209-214.

2 MALPIGHIACEAE (MALPIGHIALES)

2.1 Características gerais

A família Malpighiaceae apresenta aproximadamente 60 gêneros e 1.200 espécies de

árvores, arbustos e lianas, distribuídas pelas regiões tropicais e subtropicais, especialmente no

continente americano, onde ocorrem 44 gêneros e 800 espécies (Vicentini & Anderson 1999,

Joly 2002). O Brasil é representado por 32 gêneros, com cerca de 300 espécies, distribuídas

nas diversas regiões do país (Barroso et al. 1991). É uma das famílias mais importantes no

Cerrado em termo de diversidade (Furley 1999) contabilizando aproximadamente 62 espécies,

em sua maioria pertencentes aos gêneros Banisteriopsis e Byrsonima (Castro et al. 1999).

A morfologia das flores de Malpighiaceae é bastante homogênea. A corola possui cinco

pétalas livres, alternadas com as sépalas, e um androceu com 10 estames envolvendo um

ovário súpero tricarpelar (Anderson 1979, Joly 2002, Souto & Oliveira 2008). As flores

possuem também uma pétala modificada que atua na atração e orientação de polinizadores,

chamada de pétala estandarte ou guia (FIGURA 1A), que se distingue das demais pelo

tamanho menor e pela maior espessura da unha (Costa et al. 2006). As inflorescências são

paniculadas e surgem nas axilas superiores ou terminais. Seus frutos possuem extrema

diversidade, apresentando-se indeiscentes, secos e carnosos, e frutos secos deiscentes, que

podem ser alados ou não, glabros ou pilosos (Taylor & Crepet 1987, Vicentini & Anderson

1999). Algumas Malpighiaceae possuem sâmaras (FIGURA 1B) que podem ser utilizadas

para taxonomia quando não se conhece a espécie de origem (Mirle & Burnham 1999). As

flores possuem cinco sépalas com um par de glândulas de óleo (elaióforos) (FIGURA 1C). Às

vezes, os elaiófors aparecem sobre quatro sépalas, ficando a quinta sépala desprovida da

glândula (Barroso et al. 1991). Os elaióforos são importantes no mecanismo de polinização e

algumas espécies de Orchidaceae são consideradas miméticas das Malpighiaceae, pois

possuem estruturas similares, envolvidas também na polinização (Stpiczynska et al. 2007). os

indivíduos são perenes com folhas inteiras de disposição alterna. Nas folhas o indumento é

constituído de pêlos simples, unicelulares, implantados em elevações da epiderme e providos

de pé e de uma porção horizontal, agudos nas extremidades, denominados de pêlos

malpighiáceos. O comprimento do pé pode ser reduzido ou muito longo e apresentar

ramificações (Barroso et al. 1991).

FIGURA 1 (A) flor típica de Malpighiaceae evidenciando suas cinco pétalas, uma delas sendo mais longa, a

pétala estandarte; (B) fruto do tipo sâmara; (C) glândulas de óleo (Figura A: Farmer (2010); B: Spjut (2010); C:

Conrad (2010).

2.2 Espécies abordadas no estudo

Foram investigadas as espécies de Malpighiaceae mais abundantes na área de estudo:

Banisteriopsis malifolia (Nees & Mart.) B. Gates, B. campestris (A. Juss.) Little, B. laevifolia

(A. Juss.) B. Gates, Peixotoa tomentosa A. Juss e Byrsonima intermedia A. Juss.

Os três gêneros, Byrsonima, Banisteriopsis e Peixotoa, e suas respectivas espécies, são

reconhecidas pelos seguintes caracteres:

Byrsonima é um arbusto ereto, com inflorescências simples e constituída de racemos.

Possui brácteas e bractéolas não foliáceas e pêlos malpighiáceos com a parte superior

horizontal e furcada. Seus frutos têm a forma de drupas. A consistência das folhas é

levemente coriácea e pilosa e possuem células com cristais de oxalato de cálcio, sob a forma

de cristais isolados, geminados ou em drusas (Barroso et al. 1991).

Byrsonima intermedia A. Juss. é um arbusto que possui muitos ramos com subdivisões. A

folha é coriácea, com coloração verde escuro, de margem lisa e glabra, peciolada e sem

nectários extraflorais. Seus ramos apresentam pequenas flores amarelas com simetria bilateral

reunidas em racemos terminais. A flor é hermafrodita (completa) com corola dialipétala,

composta por cinco pétalas ungüiculadas e franjadas, sendo a pétala estandarte mais elevada

que as outras. As cinco sépalas apresentam um par de elaióforos (cada uma) na face abaxial,

totalizando 10 glândulas de óleo. Os frutos são do tipo drupa. O androceu apresenta 10

estames concêntricos, com deiscência longitudinal nas anteras. O gineceu é tricarpelar, com

os estiletes separados e as superfícies estigmáticas puntiformes localizadas internamente no

anel de anteras.

Banisteriopsis e Peixotoa são arbustos com inflorescências compostas. Em Banisteriopis

as flores contêm 10 estames férteis, desiguais entre si. Os estiletes possuem papilas

estigmáticas localizadas na porção terminal. O samarídeo tem uma porção convexa, mais

espessada e nerviforme, voltada para o centro do fruto (lado interno), com inserção do

samarídeo basal (Barroso et al. 1991).

Banisteriopsis malifolia (Ness & Martius) B. Gates é um arbusto que possui muitos ramos

com subdivisões. As folhas são coriáceas, com coloração verde escuro nas folhas adultas e

verde muito claro nas folhas jovens, a margem é lisa e há pilosidade nas duas faces, com um

par de nectários extraflorais margeando a base da nervura principal. A flor é hermafrodita

(completa) de simetria bilateral, possui cinco sépalas, com oito ou 10 elaióforos. A corola é

dialipétala, composta por cinco pétalas rosadas, ungüiculadas e franjadas, sendo a pétala

estandarte mais elevada que as outras. O androceu apresenta cinco estames concêntricos, com

estiletes separados e as superfícies estigmáticas localizadas internamente no anel de anteras.

Os frutos são tipo sâmara, com um, dois, três ou raramente quatro unidades de dispersão por

fruto (Torezan-Silingardi 2006).

Banisteriopsis laevifolia (A. Juss.) B. Gates é um arbusto com ramos pouco divididos.

Suas folhas são coriáceas, com coloração verde escuro, com margem lisa e pilosidade na face

inferior. A flor é hermafrodita (completa) de simetria bilateral, possui cinco sépalas com oito

elaióforos. A corola é dialipétala, composta por cinco pétalas amarelas, ungüiculadas e

franjadas, sendo a pétala estandarte mais elevada que as outras. O androceu apresenta 10

estames e as anteras amarelas circundam o gineceu, que é tricarpelar, com os estiletes

separados e as superfícies estigmáticas puntiformes localizadas internamente no anel de

anteras. Os frutos são do tipo sâmara, com um, dois, três ou raramente quatro unidades de

dispersão por fruto (Torezan-Silingardi 2006).

Banisteriopsis campestris (A. Juss.) Little é um arbusto cujos ramos apresentam poucas

subdivisões. As folhas são verde claro, membranosas, com a nervura bem marcada e a

margem lisa, há pilosidade nas faces abaxial e adaxial, possuem um par de nectários

extraflorais na base da nervura principal. A flor é hermafrodita (completa), de simetria

bilateral, rosada, possui cinco sépalas com oito elaióforos. A corola é dialipétala, composta

por cinco pétalas ungüiculadas e franjadas, sendo a pétala estandarte mais elevada que as

outras. O androceu apresenta oito estames concêntricos, amarelos. O gineceu é tricarpelar,

com os estiletes separados e as superfícies estigmáticas discóides localizadas internamente no

anel de anteras. Os frutos são tipo sâmara, com um, dois, três ou raramente quatro unidades de

dispersão por fruto (Torezan-Silingardi 2006, Souto & Oliveira 2008).

No gênero Peixotoa o androceu é constituído de cinco estames e cinco estaminódios com

ápice claviforme ou piriforme. As estípulas interpeciolares são cordiformes, bem

desenvolvidas, de dois ou mais centímetros de largura e concrescidas entre si. Suas umbelas

possuem quatro flores, providas na base de duas bractéolas foliáceas ovais ou cordiformes. O

ovário contém três estiletes. A forma de cristalização do oxalato de cálcio nas folhas tem

importância sistemática e os cristais geminados caracterizam as espécies de Peixotoa (Barroso

et al. 1991, Torezan-Silingardi 2006).

Peixotoa tomentosa A. Juss. é uma planta do estrato arbustivo da vegetação de cerrado.

Apresenta, geralmente, um ou dois ramos que podem chegar a três metros de altura, tem

poucas folhas e possui nectários extraflorais pares na face inferior da base das folhas (Del-

Claro et al. 1997), que também possuem pêlos malpighiáceos nas faces adaxial e abaxial.

Suas flores são amarelas e possuem oito glândulas de óleo funcionais distribuídas aos pares,

na base de quatro sépalas. As pétalas são ungüiculadas e fimbriadas. A pétala estandarte é

mais elevada que as outras. Há cinco estames funcionais com formato típico e coloração

amarela opaca, além de cinco estaminódios globosos de coloração amarela brilhante. Estames

e estaminódios ficam na mesma altura em relação à flor. Há geralmente três estiletes, cada

qual com seu estigma puntiforme. Cada flor pode produzir até três sementes aladas (raramente

quatro) do tipo sâmara (Torezan-Silingardi 2006).

2.3 Estudos em ecologia com Malpighiaceae

Estudos em ecologia de Malpighiaceae no Brasil, particularmente no cerrado, são bastante

raros. No entanto, por ser uma das famílias mais importantes do cerrado em termo de número

de espécies (Furley 1999), as Malpighiaceae são encontradas com freqüência em

levantamentos fitosociológicos.

Castro et al. (1999) em uma revisão sobre a riqueza florística do cerrado, fornecem uma

lista com as principais espécies botânicas encontradas neste bioma. Quanto às Malpighiaceae,

das 61 espécies desta família abordadas, os gêneros mais representativos são Byrsonima, com

31 espécies e Banisteriopsis, com 13 espécies encontradas. Banisteriopsis campestris, B.

laevifolia, B. malifolia e Byrsonima intermedia foram amostradas enquanto que Peixotoa

tomentosa não foi listada neste inventário. No entanto, os próprios autores admitem um erro

na estimativa de riqueza de espécies, visto que os estudos revisados não abrangem toda a área

geográfica do cerrado. Este padrão de maior riqueza de Byrsonima também foi evidenciado

no levantamento feito por Saporetti Jr et al. (2003) em uma área de cerrado no centro-oeste de

Minas Gerais. Das quatro espécies amostradas, três pertenciam ao gênero Byrsonima, sendo

que B. intermedia foi uma das plantas mais abundantes na área, quando comparada a todas as

outras espécies botânicas amostradas. Byrsonima também foi representado no levantamento

realizado por Campos et al. (2006) em um gradiente de cerradão e cerrado, perfazendo duas

das três espécies de Malpighiaceae encontradas.

Na revisão de Castro et al. (1999) o gênero Heteropterys aparece com oito espécies

ocorrendo no cerrado. Schmidt et al. (2005) estudando efeitos do fogo sobre uma população

de Heteropterys pteropetala (Adr. Juss.), verificaram que queimadas prolongadas podem

afetar a viabilidade e a germinação da espécie, porém os diásporos podem resistir às

queimadas caso estejam enterrados no solo. Ainda, queimadas precoces (junho) prejudicam o

recrutamento e crescimento dos indivíduos, além de influenciar a distribuição espacial da

população. Byrsonima também é o gênero mais estudado com relação a interações inseto-

planta, muito provavelmente devido a sua grande ocorrência e abundância no cerrado

(Saporetti Jr. et al. 2003, Campos et al. 2006).

Estudando os efeitos de formigas do gênero Camponotus na comunidade de insetos em

inflorescências de Byrsonima crassifolia (L.) Kunth, Fernandes et al. (2005), constataram que

inflorescências em ramos onde formigas estavam presentes foram significativamente menos

atacadas por insetos mastigadores e sugadores do que inflorescências em ramos com formigas

excluídas. Estes resultados sugerem então que a presença de formigas influencia a estrutura da

comunidade de insetos herbívoros associados com B. crassifolia.

Em outro estudo com formigas, Leal & Oliveira (1998), observaram que indivíduos da

tribo Attini utilizavam os frutos de Byrsonima intermedia para criar fungos e deste modo

serviam de agentes dispersores secundários, já que as sementes de B. intermedia são dispersas

primariamente por aves que se alimentam das drupas. Estes autores sugerem que as formigas

se alimentam da polpa dos frutos reduzindo a infestação por fungos e aumentando a taxa de

germinação das sementes.

Galhas também fazem uso de Byrsonima intermedia e também ocorrem em outras três

espécies de Malpighiaceae (Banisteropsis pubipetala, B. pubipetala e Heteropterys

byrsonimifolia) em uma reserva de cerrado no estado de São Paulo (Urso-Guimarães &

Scareli-Santos 2006). Para Byrsonima sericea DC., presentes em restingas, Flinte et al. (2006),

constataram que os meses de outubro e dezembro eram os que apresentavam as maiores

freqüências de plantas atacadas pelos galhadores, tanto Diptera quanto Lepidoptera.

Outros estudos com Malpighiaceae dizem respeito à biologia reprodutiva (Sigrist &

Sazima 2004, Costa et al. 2006) e polinização por abelhas da tribo Centridini (Ramalho &

Silva 2002). Rego et al. (2006) fornecem uma lista com nove malpighiaceaes em diferentes

ecossistemas que são visitadas por abelhas da espécie Centris flavifrons (Friese), (Byrsonima

crassifolia (L.) Kunth, Byrsonima sericea A.DC., Byrsonima amoena Cuatrec., Byrsonima

intermedia A. Juss., Byrsonima coccolobifolia Kunth, Mcvaughia bahiana W.R. Anderson,

Banisteriopsis sp. Malpighia glabra L. e Malpighia punicifolia L.) e adiciona a espécie

Tetrapterys sp. à lista prévia.

Além de polinizadores, as malpighiáceas suportam uma grande gama de insetos fitófagos.

Flinte et al. (2006) encontraram um total de 45 espécies de insetos associados à Byrsonima

sericea DC., sendo 20 de lepidópteros exofíticos, 17 de coleópteros exofíticos, quatro de

minadores e quatro de galhadores. Já Del-Claro et al. (1997) constataram que tripes eram o

principais herbívoros das estruturas reprodutivas de Peixotoa tomentosa. O pequeno tamanho

dos tripes permitia que estes insetos se escondessem abaixo das sépalas, nas câmaras florais,

onde formigas predadoras de tamanho grande não conseguiam entrar.

Percebe-se com estes estudos citados acima que Malpighiaceae possui uma grande

diversidade quanto à entomofauna associada e dada sua grande abrangência,

representatividade e significância no cerrado (Furley 1999), esta família botânica tem

recebido pouca atenção quanto à interações ecológicas.

Segundo Flinte et al. (2006) a escolha de plantas representativas, com ampla distribuição

geográfica, como Malpighiaceae, é promissora para o estudo comparativo da entomofauna

associada, uma vez que fornece subsídios para definir padrões temporais e avaliar a

importância de fatores ambientais sobre a comunidade de insetos fitófagos.

2.4 REFERÊNCIAS BIBLIOGRÁFICAS

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CAMPOS, E. P., T. G. DUARTE, A. V. NÉRI, A. F. SILVA, J. A. A. MEIRA-NETO, and G. E.

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CASTRO, A. A. J. F., F. R. MARTINS, J. Y. TAMASHIRO, and G. J. SHEPHERD. 1999. How rich is

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COSTA, C. B. N., J. A. COSTA, and M. RAMALHO. 2006. Biologia reprodutiva de espécies

simpátricas de Malpighiaceae em dunas costeiras da Bahia, Brasil. Revista Brasilileira de

Botânica 29: 103-114.

DEL-CLARO, K., R. MARULLO, and L. A. MOUND. 1997. A new Brazilian species of

Heterothrips (Insecta; Thysanoptera) interacting with ants in Peixotoa tomentosa flowers

(Malpighiaceae). Journal of Natural History 31: 1307-1312.

FARMER, M. 2010. A Neotropical Savanna, learning a savanna in Panama, plant by plant.

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FERNANDES, G. W., M. FAGUNDES, M. K. B. GRECO, M. S. BARBEITOS, and J. C. SANTOS.

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inflorescences of Byrsonima crassifolia (Linnaeus) H.B.K. (Malpighiaceae). Revista

Brasileira de Entomologia 49: 264-269.

FLINTE, V., C. O. ARAÚJO, M. V. MACEDO, and R. F. MONTEIRO. 2006. Insetos fitófagos

associados ao murici da praia, Byrsonima sericea (Malpighiaceae), na Restinga de Jurubatiba

(RJ). Revista Brasileira de Entomologia 50: 512-523.

FURLEY, P. A. 1999. The nature and diversity of neotropical savanna vegetation with

particular reference to the Brazilian cerrados. Global Ecology and Biogeography 8: 223-241.

JOLY, A. B. 2002. Botânica: Introdução à taxonomia vegetal. Companhia Editora Nacional,

São Paulo.

LEAL, I., R., and P. S. OLIVEIRA. 1998. Interactions between fungus-growing ants (Attini),

fruits and seeds in Cerrado vegetation in Southeast Brazil. Biotropica 30: 170-178.

MIRLE, C., and R. J. BURNHAM. 1999. Identification of asymmetrically winged samaras from

the Western Hemisphere. Brittonia 51: 1-14.

RAMALHO, M., and S. SILVA. 2002. Flora oleífera e sua guilda de abelhas em uma

comunidade de restinga tropical. Sitientibus Série Ciências Biológicas 2 34-43.

REGO, M. M. C., P. M. C. ALBUQUERQUE, M. C. RAMOS, and L. M. CARREIRA. 2006. Aspectos

da biologia de nidificação de Centris flavifrons (Friese) (Hymenoptera: Apidae, Centridini),

um dos principais polinizadores do murici (Byrsonima crassifolia L. Kunth, Malpighiaceae),

no Maranhão. Neotropical Entomology 35: 579-587.

SAPORETTI JR., A. W., J. A. A. M. NETO, and R. P. ALMADO. 2003. Fitossociologia de Cerrado

Sensu Stricto no município de Abaeté-MG. Árvore, Viçosa 27: 413-419

SCHMIDT, I. B., A. B. SAMPAIO, and F. BORGHETTI. 2005. Efeitos da época de queima sobre a

reprodução sexuada e estrutura populacional de Heteropterys pteropetala (Adr. Juss.),

Malpighiaceae, em áreas de Cerrado sensu stricto submetidas a queimas bienais. Acta

Botânica Brasílica 19: 927-934.

SIGRIST, M. R., and M. SAZIMA. 2004. Pollination and reproductive biology of twelve species

of neotropical malpighiaceae: Stigma morphology and its implications for the breeding

system. Annals of Botany 94: 33-41.

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espécies de Banisteriopsis C.B. Robinson e Diplopterys A. Juss. (Malpighiaceae). Acta

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contrasting members of Oncidiinae (Orchidaceae). Botanical Journal of the Linnean Society

155: 135-148.

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early plant-pollinator relationship. American Journal of Botany 74: 274-286.

TOREZAN-SILINGARDI, H. M. 2006. Influência da variação ambiental na frutificação de

espécies da família Malpighiaceae no Cerrado. Tese de Doutorado. p. 79. Universidade de

São Paulo. Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto. Programa de Pós

Graduação em Entomologia, São Paulo, SP.

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from the Pé-De-Gigante Cerrado reserve, Santa Rita do Passa Quatro, SP, Brazil. Brazilian

Journal of Biology 66: 357-369.

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Hopkins, A. Vicentini, C. A. Sothers, M. A. S. Costa, J. M. Brito, M. A. D. Souza, L. H. P.

Martins, L. G. Lohmann, P. A. C. L. Assunção, E. C. Pereira, C. F. Silva, M. R. Mesquita and

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de uma floresta de terra firme na Amazônia Central, pp. 505-511. INPA-DFID, Manaus.

A IMPORTÂNCIA DA FLORAÇÃO SEQÜENCIAL DE MALPIGHIACEAE PARA A

MANUTENÇÃO DE TRIPES (THYSANOPTERA) NO CERRADO

1 INTRODUÇÃO

Tripes são insetos onipresentes, em sua maioria fitófagos, micófagos ou predadores,

(Mound 2002a, Mound & Morris 2007). Muitas espécies são abundantes em estruturas de

vários táxons, principalmente flores de angiospermas (Mound & Terry 2001, Mound 2005) e

os padrões de abundância e ocorrência em muitas plantas são fatores importantes que

determinam a dinâmica de populações de tripes (Ananthakrishnan 1993, Morse & Hoddle

2006). No entanto estas relações são raramente consideradas. A maioria dos registros relativos

a populações de tripes compreende estudos de curta duração em culturas economicamente

importantes (Childers & Bullock 1999, Dreistadt et al. 2007) e com poucas exceções (Cho et

al. 2000, Pearsal & Myers 2001, Seal et al. 2006) os pesquisadores não levam em

consideração o número de espécies envolvidas, a partição de recursos, ou mesmo a

diversidade entre os habitats.

Geralmente a abundância e diversidade de tripes estão ligadas a características estruturais

do meio ambiente que ocorrem em uma escala específica (Pinent et al. 2006) refletindo

importantes requisitos no habitat como disponibilidade de espaço, fuga de predadores,

eficiência no forrageamento e facilidades reprodutivas (Strauss & Karban 1994, Del-Claro,

1998, Mound & Terry 2001, Carvalho et al. 2006). As plantas que oferecem estes benefícios

são definidas por Mound & Marullo (1996) como plantas hospedeiras eficazes ou verdadeiras

de tripes (Mound & Marullo 1996). Como a fenologia das plantas muda no decorrer do ano

dependendo das variações sazonais (Gill et al. 1998), os tripes, assim como outros insetos,

devem procurar por microhabitats favoráveis, migrando entre hospedeiros ao longo do ano

(Barbosa 1988, Mound & Marullo 1996).

Milne & Walter (2000) deram uma abordagem diferente à classificação de plantas

hospedeiras de tripes, estabelecendo os termos “hospedeiros primários” e “secundários”,

levando em consideração como um habitat seria bom em sustentar populações de tripes. A

necessidade para esta caracterização recai no fato de que em alguns casos tripes alternam

entre hospedeiros somente para conseguir alimento e outros recursos que permitam a eles

sobreviverem, mas não se reproduzir; ou tripes adultos podem se acumular em massa em

hospedeiros secundários ou temporários, mas em quantidades menores se comparados aos

hospedeiros principais. Assim sendo, as espécies de tripes podem se reproduzir e atingir picos

de abundância somente em seus hospedeiros primários, e quando estes não estão disponíveis,

tripes sobrevivem com poucos indivíduos em hospedeiros secundários. Deste modo, a

alternância entre hospedeiros parece ter uma forte influência no valor adaptativo de tripes

(Barbosa 1988, Ananthakrishnan 1993). Ainda, a presença ou qualidade de estruturas

específicas presentes nos hospedeiros primários podem determinar a abundancia de espécies e

a diversidade de tripes (Pinent et al. 2005, Cavalleri et al. 2006).

Cerca de 6000 espécies de tripes são conhecidas mundialmente e o Brasil é representado

por 700 espécies (Mound 2002b, Mound & Morris 2007). Apesar de existirem algumas

pesquisas realizadas com tripes no Brasil, a maioria restringe estes insetos a pragas e vetores

de viroses na agricultura (Monteiro et al. 1998, Nagata et al. 1999). Considerando o Cerrado

brasileiro como um importante bioma do Brasil (Furley & Ratter, 1988, Oliveira & Marquis

2002), é surpreendente o fato de que pouco é conhecido a respeito dos tripes associados a

plantas de comum ocorrência neste bioma. Até agora um grande número de tripes foi

encontrado provocando danos nas flores de Peixotoa tomentosa A. Juss., (Malpighiaceae)

(Del-Claro et al. 1997). Esta família botânica exibe uma morfologia floral bastante

conservativa e partilha a mesma guilda de polinizadores (Anderson 1979). Observações

posteriores sugeriram que uma comunidade de Malpighiaceae no cerrado apresentava floração

seqüencial e abrigava uma grande comunidade de tripes (Torezan-Silingardi, 2006).

A avaliação da abundância de tripes ao longo do ano em plantas de floração seqüencial

pode fornecer informações sobre a importância de cada hospedeiro em sustentar populações

de tripes. Nos neotrópicos, casos de floração seqüencial foram extensivamente estudados para

Bromeliaceae (Araujo et al. 1994, Varassin & Sazima 2000, Siqueira Filho & Machado 2001,

Machado & Semir 2006, Marques & Lemos Filho 2008). Todos estes autores concordam que

a floração seqüencial das bromeliáceas pode ser de extrema importância para a manutenção de

polinizadores em uma determinada área. Machado & Semir (2006) relataram floração

seqüencial em 14 bromeliáceas na Mata Atlântica no Brasil. No nível de comunidade, certas

espécies de plantas podem facilitar a polinização de outras espécies. A facilitação ocorre

quando espécies que florescem primeiro sustentam polinizadores que posteriormente visitam

as espécies que florescem tardiamente (“mutualismo seqüencial” Waser & Real 1979, Brody

1997), assim é esperado que a comunidade dependente de recursos florais acompanhe os

ciclos de floração (Appanah 1985). Considerando-se que muitas espécies de tripes

neotropicais não sofrem diapausa devido às altas temperaturas nesta região e são ativos

durante o ano todo (Van Houten et al. 1995, Murai 2000) podemos assumir que as

malpighiáceas com floração seqüencial têm um papel significativo em fornecer microhabitats

para tripes em diferentes estações.

Para se entender a função ecológica de cada planta na ecologia de um inseto herbívoro,

dois principais critérios precisam ser quantificados: a regularidade temporal em que os

individuos em diferentes estágios de desenvolvimento são encontrados na planta; e sua

abundância em uma planta particularmente a outras (Walter & Benfield 1994, Milne & Walter

2000). Sugere-se que a escolha de plantas representativas, com grande abrangência geográfica,

como as malpighiáceas, é promissora para o estudo comparativo da thysanopterofauna

associada, uma vez que pode fornecer informações que auxiliem na definição de padrões

temporais de ocorrência e permitam examinar a importância de fatores ambientais na

comunidade destes insetos (Flinte et al. 2006).

Neste estudo nós testamos a hipótese de que a floração seqüencial das malpighiáceas é

responsável pela manutenção de tripes ao longo do ano, assumindo a premissa de que tripes

migram entre diferentes plantas de acordo com a fenologia de floração. Além disso, também

procuramos 1) identificar as espécies de tripes presentes em Malpighiaceae; 2) classificar as

diferentes plantas como hospedeiros principais ou secundários; 3) buscar relações entre a

abundância de tripes e o tamanho das flores e ainda 4) buscamos verificar se as variações

sazonais tiveram influência na abundância e diversidade de tripes.

2 CONCLUSÃO

Neste estudo nós amostramos 19 espécies de tripes das quais as mais importantes foram

Frankliniella condei, Heterothrips peixotoa e Scutothrips nudus e mostramos que a floração

seqüencial das malpighiáceas tem um importante papel na manutenção da comunidade de

tripes ao longo do ano, principalmente para Heterothrips peixotoa, a espécie de tripes mais

abundante em todas as amostragens que tem por hospedeiros principais Peixotoa tomentosa e

Banisteriopsis laevifolia. A riqueza e diversidade de Thysanoptera em Malpighiaceae são as

maiores já registradas para tripes em um grupo de plantas relacionadas taxonomicamente,

possivelmente devido ao aspecto conservativo das malpighiáceas que podem fornecer

alimento e proteção contra predadores. Flores maiores abrigavam uma quantidade maior de

tripes e a fenologia das plantas foi tão importante quanto o clima na manutenção destes

insetos nas malpighiáceas. Estudos futuros prevêem o exame dos danos ou benefícios

provenientes da ocupação dos hospedeiros por tripes como também a análise da ocorrência

destes insetos em outras plantas comuns no cerrado.

3 INTRODUCTION

Thrips are ubiquitous insects, mainly phytophagous, mycophagous or predatory in habit

(Mound 2002a, Mound & Morris 2007). Many species are abundant in structures of a wide

range of plant taxa, mostly in flowers of Angiosperms (Mound & Terry 2001, Mound 2005)

and the patterns of abundance and occurrence in several plants are important factors that

determine the population dynamics of thrips (Ananthakrishnan 1993, Morse & Hoddle 2006).

However these relationships are rarely considered. Massive records comprise short period

studies of thrips populations in economical important crops (Childers & Bullock 1999,

Dreistadt et al. 2007) and with a few exceptions (Cho et al. 2000, Pearsall & Myers 2001,

Seal et al. 2006) researchers often do not take into account the number of species involved,

the portioning of resources and thrips intra and inter habitat diversity.

Generally, species abundance and diversity of thrips are linked to structural characteristics

of environment that occur on a specific scale (Pinent et al. 2006) reflecting important habitat

requirements such as space availability, escape from predation, foraging efficiency and

reproductive needs (for examples see Strauss & Karban 1994, Del-Claro 1998, Terry 2001,

Carvalho et al. 2006). The plants which offer these benefits are defined by Mound & Marullo

(1996) as effective thrips host plants. As plant phenology changes along the year depending

on habitat seasonal variations (Gill et al. 1998), thrips, just like other insects, will search for

more favorable microhabitats, moving between hosts throughout the year (Barbosa 1988).

Milne & Walter (2000) gave a different approach to the classification of thrips host plants,

establishing the terms “major” and “minor” hosts, taking into account how good the habitat

might be in supporting thrips populations. The need for this characterization relies in the fact

that in some cases thrips alternate the hosts only in order to get food and other resources that

allow them to survive, but not to reproduce; or adult thrips can accumulate in mass in

secondary or temporary hosts (minor hosts), but in smaller densities when compared to the

major ones. So thrips species can reproduce and reach a peak of abundance only in its major

hosts, while surviving with a few individuals in minor hosts, when the major ones are not

available in time and space. Therefore, the alternation of hosts seems to have a strong

influence in thrips fitness (Barbosa 1988, Ananthakrishnan 1993). In addition, the presence or

quality of major host specific structures may determine species abundance and in some cases

the richness and diversity of thrips species (Pinent et al. 2005, Cavalleri et al. 2006).

About 6000 species of thrips are known worldwide and Brazil is represented by 700

species (Mound 2002b, Mound & Morris 2007). Although some research has been carried out

with thrips in Brazil, the majority restrict these insects as agricultural pests and crop virus

vectors (Monteiro et al. 1998, Nagata et al. 1999). Considering the Brazilian Savanna

(Cerrado) an important biome from Brazil (Furley & Ratter 1988, Oliveira & Marquis 2002),

it is surprising that little is known about the thrips associated with the plants of common

occurrence in this biome. So far, great densities of thrips were found damaging flowers of

Peixotoa tomentosa A. Juss., an oil-rewarding Malpighiaceae (Del-Claro et al. 1997). This

botanical family exhibits highly conservative floral morphology and shares the same guild of

pollinators (Anderson 1979). Previous observations and evidence suggested that

Malpighiaceae community in an area of Cerrado presented sequential flowering and

supported a whole thrips assemblage (Torezan-Silingardi 2006).

The evaluation of the abundance in thrips community along the year in sequential

flowering plant species can provide information about the importance of each host in

supporting thrips populations. In neotropics cases of sequential flowering were extensively

studied for Bromeliaceae (Araujo et al. 1994, Varassin & Sazima 2000, Siqueira Filho &

Machado 2001, Machado & Semir 2006, Marques & Lemos Filho 2008). All these authors

agree that Bromeliaceae sequential flowering may be of extreme importance for the

maintenance of pollinators in a given area. Machado & Semir (2006) reported sequential

flowering in 14 Bromeliaceae at Atlantic Rain Forest in Brazil. At the community level, plant

species may facilitate one another’s pollination. Facilitation occurs when early-flowering

species support pollinators that then visit later-flowering species ("sequential mutualism"

sensu Waser & Real 1979, Brody 1997) so the animal community dependent on flower

resources can be expected to follow the cycles of flowering (Appanah 1985). Given that many

Neotropical thrips are not supposed to overwinter due the high temperatures (see Van Houten

et al. 1995, Murai 2000) and are active throughout the year we may assume that sequential

flowering Malpighiaceae play a significant role to provide thrips microhabitats in different

seasons.

To understand the role of each plant species in the ecology of an herbivore insect, two

principal criteria need to be quantified: the regularity with which individuals of the different

life stages are found on a plant species over time, and their abundance on that particular plant

species relative to other plant species (Walter & Benfield 1994, Milne & Walter 2000). It is

suggested that the choice of representative plants, with wide geographical distribution, like

some Malpighiaceae, is promising for the comparative study of the associated

thysanopterofauna, once it can supply subsidies to define temporary patterns and to evaluate

the importance of environmental factors on the community of these insects (Flinte et al. 2006).

In this study we tested the hypothesis that Malpighiaceae sequential flowering is

responsible for the maintenance of thrips throughout the year, assuming the premise that

thrips migrate among different plants according to the flowering phenology. Moreover we 1)

aimed to identify the species of thrips present in Malpighiaceae; 2) to classify the different

plants as major or minor hosts and 3) seek for relations between thrips abundance and the size

of flowers and 4) to verify if seasonal variations in the habitat and host plant phenology had

influence on thrips abundance and diversity.

4 MATERIAL AND METHODS

4.1 Study area

Fieldwork was carried out from March 2007 to February 2009 in an area of Cerrado

vegetation (sensu Goodland 1971) at the Ecological Reserve of Clube de Caça e Pesca Itororó

de Uberlândia (CCPIU, 640 ha, 18º97’S, 48º29’W; 863m) in Uberlândia municipality, Minas

Gerais State, Brazil (FIGURE 1). Cerrado senso strictu (savanna woodland) is the main

vegetation type in the reserve. This vegetation is dominated by trees and shrubs often 2–4m

tall and a fair amount of herbaceous vegetation (Oliveira-Filho & Ratter 2002). The climate in

the region present two well characterized seasons, a dry winter (May to September) and rainy

summer (October to March) (see Reu & Del-Claro 2005 for details about the study site).

FIGURE 1. Aerial photograph of the Clube Caça e Pesca Itororó de Uberlândia where the fieldwork was carried

out. The opaque polygon indicates the place where the fieldwork was carried out. On the North, at the top of the

photo, the downtown of Uberlândia municipality. Surrounding the field area there is a predominance of crop

fields. (Point of view altitude 4.88km, photo by Google Earth (2009).

4.2 Preliminary observations

Initially, throughout 2007, we sampled the most abundant Malpighiaceae present in the

study area in order to verify the plant species in which thrips were most common associated.

Samplings were made at the peak flowering, based on Torezan-Silingardi (2006).

A single plant of the appropriate species was selected and 5 flowers in anthesis were

collected and conserved in 60% ethanol (Milne & Walter 2000). The 2007 results indicated

that thrips were more abundant in flowers of Banisteriopsis malifolia (Nees & Mart.) B. Gates,

B. campestris (A. Juss) Little, B. laevifolia (A. Juss.) B. Gates, Byrsonima intermedia A. Juss.,

and Peixotoa tomentosa A. Juss. (FIGURE 2). This Malpighiaceae community was supposed

to present sequential flowering and shrubs of all are very common in the study area (Torezan-

Silingardi 2006). Hereafter the species Byrsonima intermedia will be presented without

abbreviation in order to avoid confusion with the Banisteriopsis species.

FIGURE 2. A) Banisteriopsis malifolia; B) Banisteriopsis campestris; C) Banisteriopsis laevifolia; D) Peixotoa

tomentosa; E) Byrsonima intermedia. (Photos A-D: by Estevão Alves-Silva; E – by Helena Maura Torezan

Silingardi)

4.3 Data collecting

Once the Malpighiaceae species were chosen, thrips samplings started in March 2008,

when B. malifolia was flowering. Data collecting covered an entire year, from March 2008 to

February 2009, with samples being taken every two weeks. In each sampling five individuals

of each species were randomly chosen and five flowers in anthesis were collected. This

procedure was made until flowers were present in the plant. No plant individuals were

sampled more than once, to avoid pseudo-replication of data (Hulbert 1984). The same

procedure adopted for B. malifolia was made in the other four plants: P. tomentosa, B.

laevifolia, Byrsonima intermedia and B. campestris. In the case of overlapping flowering

between two species, flowers of both were collected.

The sampling methodology adopted for determining thrips abundace in the flowers was

the destructive sampling in which the flowers were extracted from the plants and thrips

evaluation (species and number of individuals) was made in laboratory conditions. According

to Pearsall & Myers (2000) this is the best technique for thrips detection because samples are

likely to be less biased and more appropriate for population monitoring. The flowers were

involved with a plastic sack to avoid the escape of the thrips before the cutting and then kept

individually in 60% ethanol. During the samplings some sporadic behavioral observations of

thrips and other arthropod were made on the plants.

Thrips were mounted in microscope slides according to Mound & Marullo (1996) and the

species were primarily identified with keys from different authors (Mound & Marullo 1996,

Monteiro unpubl. data, Milne et al. 1997, Monteiro et al. 2001, Arevalo et al. 2006). Species

level identification was possible only with the collaboration of Dr. Laurence A. Mound

(Commonwealth Scientific and Industrial Research Organisation, Australia). However, in

many cases it was not possible to reach species level, either because the specimens are

undescribed (new species and in some cases new genera) or because the difficulty in

recognize certain intraspecific polymorphic taxonomic patterns inherent to many species.

Additionally, Neotropical thysanopterofauna is poorly known and species not related to crops

are seldom studied. In those cases in which it was not possible to determine the species, the

individuals were presented by genera and morphospecified.

4.4 Thysanopterofauna descriptions

Thysanopterofauna descriptions included the following indexes according to Ludwig &

Raynolds (1988), Manly (1997), Lansac-Tôha et al. (2000), Ott & Carvalho (2001), Magurran

(2004) and Uramoto et al. (2005).

Richness: total number of thrips species observed in each plant species.

Constancy index: it was calculated for each one of the five Malpighiaceae species and their

associated thrips. The formula was given by “C=p(100)/N” where p was the number of

samples in that a given thrips taxa was recorded and N was the total number of samples for

each plant. According to this index, constant taxa were considered to be those that occurred in

more than 50% of the samples, accessory taxa those occurring in 25% to 49.9% of the

samples and accidental taxa those occurring in less than 24.9% of the samples.

Number of dominant species: it was calculated for each one of the five Malpighiaceae

species and their associated thrips. Species dominance was defined as D%=(i/t).100, where i

was the total number of individuals of a given species and T was the total number of

individuals collected. The categories were established as: eudominant>10%; dominant=5-

10%; subdominant=2-5%; eventual=1-2% and rare<1%.

Jacknife index: used to estimate the species richness in the samplings. We used the formula:

J = S+{(n-1)/n} ƒ, where S was the total number of species observed in all samples, n was the

number of samples and ƒ was the number of a single species recorded in just one of the n

samples.

Simpson index: represented the probability that two randomly selected individuals in any two

consecutively sampling belonged to the same species. It ranged from 0 to 1, with 0

representing infinite diversity and 1 representing no diversity. The formula was D = ∑ n(n-

1)/N(N-1), where n was the total number of organisms of a particular species

and N was the total number of organisms of all species.

Species evenness is a diversity index, a measure of biodiversity which quantifies how equal

the communities are numerically. When all species in a sample are equally abundant, the

species evenness assumes its maximum value. It was calculated by the formula: E=H’/H’max

where H’ was the Shannon index and H’max was the natural logarithm of the number of

species in a given plant. E was constrained between 0 and 1. The less variation in

communities among the species, the higher E will be.

Shannon index: is a measure of diversity and was used to compare the thrips diversity in

each plant species. The calculation was made by the following formula H

= -

nini

The proportion of species i relative to the total number of species (p

) was calculated, and then

multiplied by the natural logarithm of this proportion (lnp

). The resulting product was

summed across species, and multiplied by -1: A low Shannon index indicates low diversity.

4.5 Flower size and the abundance of thrips

To analyze the influence of flower size in the abundance of thrips, a portion of the flowers

used for thrips sampling (N=60 flowers of each Malpighiaceae species) were measured. A

caliper (1/10 mm accuracy) was used to evaluate the distance between the two petals adjacent

to the flag petal, named here as flower diameter. Data of thrips abundance and the diameter of

flowers were then submitted to a procedure known as Curve Adjustment test, provided by

Bioestat 5.0 software. This technique is used to demonstrate if the data has linear, power,

logarithmic or geometric distribution and regression is made simultaneously. The highest

value of R² provided in the different regressions shows which regression type is more

appropriate for the data.

The same measurements obtained for flowers of different Malpighiaceae species were also

tested in order to verify differences among the flower sizes, evidenced by a Kruskal-Wallis

test.

4.6 Environmental data

Data of rainfall (mm), mean temperature and relative humidity from March 2008 to

February 2009 were obtained from the Laboratório de Climatologia, Instituto de Geografia of

the Universidade Federal de Uberlândia, MG, Brazil. The month values of each environment

parameter were tested for linear regression with thrips monthly abundance in the plants.

4.7 Plant phenology

Each plant species had 20 adult individuals randomly chosen for the phonological

observations, in order to detect changes in the reproductive phenology throughout the year.

These plants were not used for thrips sampling. Observations were made every 15 days. The

intensity of each plant phenological event was scored from 0 to 4; meaning respectively, 0, 1–

25, 26–50, 51–75, or 76–100 percent of flowers present (sensu Morellato et al. 2000) and the

mean of each month was used for statistical functions.

The patterns of flowering were made according to Newstrom et al. (1994) who consider a

continuum from continuous to very infrequent flowering. Classes are based on frequency,

defined as the number of cycles per year (one cycle consists of a flowering episode followed

by a non-flowering interval). The four basic classes are continual (flowering with sporadic

briefs), subannual (flowering in more than once cycle per year), annual (only one major cycle

per year) and supra-annual (one cycle over more than one year). Brief flowering was

understood as a period lesser than 1 month , intermediate flowering as a period from 1 to 5

months and extended flowering as a period over than 5 months.

4.8 Testing the occurrence of seasonality

We performed circular statistical analysis of directional (circular) data, using the

phenology values measured for plant species. Months were converted into single numerical

variables. Each month was given a number from 1 to 12, starting with January and combined

with its respective value of plant phenology. Circular statistics provided (1) the mean angle a,

meaning the time of the year in which the dates of a given phenophase, in our case the

flowering, occurred at most; (2) the Rayleigh test (z) which determines the significance of the

mean angle and (3) the vector r, which is a measure of concentration around the mean angle.

In directional analysis the interest relies in the direction and not in the magnitude of the vector

r and therefore it is unitless, ranging from zero (when phenological activity is distributed

uniformly throughout the year) to one (when phenological activity is concentrated around one

time of year) and indicates the degree of asymmetry or the degree of seasonality (Fisher 1996,

Aradottir et al. 1997, Morellato et al. 2000, Jammalamadaka & Sengupta 2001). As we

predicted that the flower phenology of plants would have seasonality, that is, each species

would not flower uniformly over the year, we expected that there would be a significant angle

or mean direction observed in the circular statistics, denoted by r tending to one.

5. RESULTS

Thrips sampling in all 675 flowers from all plants studied accomplished 3788 (5.61±6.49,

±1SD) individuals distributed in 2626 (3.89±4.95,

±1SD) adults and 1162 (1.72±3.10,

±1SD) immatures. We identified 19 species of thrips in eight genera and three families:

Phlaeothripidae, Thripidae and Heterothripidae. This latter was the most abundant family in

all plants (FIGURE 3).

The plant which presented more thrips was P. tomentosa (10.4±8.0,

±1SD, n=1561

thrips in 150 flowers) followed by B. laevifolia (11.41±7.37,

±1SD, n=856 thrips in 75

flowers), B. malifolia (3.26±3.19,

±1SD, n=489 thrips in 150 flowers), B. campestris

(3.11±3.03,

±1SD, n=467 thrips in 150 flowers) and Byrsonima intermedia (2.74±4.45,

n=411 thrips in 150 flowers). Kruskal-Wallis test (H=195.7355, df=4, p<0.0001) and Dunn’s

method of multiple comparisons revealed statistical significant differences between all plants

concerning the number of thrips sampled per plant (FIGURE 4A).

Thripidae

Total

Heterothripidae

Phlaeothripidae

N. i

Thripidae

Total

Heterothripidae

Phlaeothripidae

N. i

Thripidae

Total

Heterothripidae

Phlaeothripidae

N. i

Thripidae

Total

Heterothripidae

Phlaeothripidae

N. i

Thripidae

Total

Heterothripidae

Phlaeothripidae

N. i

Banisteriopsis

malifolia

Peixotoa

tomentosa

Banisteriopsis

laevifolia

Byrsonima

intermedia

Banisteriopsis

campestris

Number of thrips per plant

200

400

600

800

1000

1200

1400

1600

1800

FIGURE 3. Thrips (total number of individuals and individuals per thrips family) observed in flowers of

Malpighiaceae species in the Brazilian savanna. N.i – means “not identified species”.

Bma Pto Bla Byi Bca

Thrips abundance

*** ***

Heterothripidae

Phlaeot

Thripidae

Hetero ThripPhlaeo

-2.0

6.5

15.0

23.5

32.0

Thrips abundance

FIGURE 4. (A) Thrips (

± 1SD) observed in flowers of Malpighiaceae species of Brazilian Savanna

vegetation: Bma - Banisteriopsis malifolia, Pto - Peixotoa tomentosa, Bla - Banisteriopsis laevifolia, Byi -

Byrsonima intermedia, Bca - Banisteriopsis campestris; (B) The number of all thrips (

± 1SD) observed in all

samplings, divided per thrips families: Hetero – Heterothripidae, Phlaeo – Phaleothripidae, Thrip – Thripidae.

*** means statistical differences (p<0.0001, Kruskal-Wallis test). Lowercase letters upon the bars indicate

significant statistical differences (p <0.0001, Dunn’s test for multiple comparisons).

The most abundant family, Heterothripidae (4.13±5.61,

±1SD, n=2790 individuals in

675 flowers) (H=495.24, df=2, p<0.0001) (FIGURE 2B) accounted for eight species in which

only to Scutothrips nudus (Moulton, 1932) and Heterothrips peixotoa Del-Claro, Marullo and

Mound 1997 the species level identification was possible. The other species were identified to

genera and were named as “Heterothrips sp. 1” to “Heterothrips sp. 5” and Lenkothrips sp.

Thripidae (0.94±1.99;

±1SD, n=633 individuals in 675 flowers) was represented by six

species: Frankliniella condei John, 1928, Frankliniella minuta (Moulton), Frankliniella

schultzei (Trybom), Frankliniella occidentalis (Pergande), Frankliniella sp. 1 and

Halmathrips (Demetriothrips) sp. The family Phlaeothripidae (0.22±0.96;

±1SD, n=148

individuals in 675 flowers) was represented by Haplothrips gowdeyi (Franklin 1908) and

other four morphospecies: three Pseudophilothrips and one Liothrips (TABLE 1). All the

morphospecies listed by genus are currently being studied and most of them are likely new

species (Laurence Mound, pers. comm). As soon the information about these species is

available, the results will be brought out.

Heterothrips peixotoa was the most frequent species in all plants and considered constant

in P. tomentosa and B. laevifolia. In the other plants this species was classified as accessory.

Heterothrips peixotoa was also the only eudominant species in all plants. The only thrips

present in all plants were F. condei, H. peixotoa, S. nudus and Frankliniella sp. 1. but

immatures identification was not possible for Frankliniella sp. 1.

Heterothrips peixotoa was seen early in the morning wandering on the petals and anthers,

where it feed (FIGURE 5). Usually no more than three individuals were seen and at the

lighter disturbance (shaking of flowers) these thrips took flight, in this occasion the thrips

stayed still, opened the wings and rapidly disappeared. In the other hand Frankliniella instead

of flighting it firstly leaped on the petals and in case the disturbance continued, the thrips flew

away. Heterothrips peixotoa was active during all the day. Foraging behavior took place in

the mornings, until 1100h approximately and during the hottest part of day, from 1100h to

1500h thrips often stayed inside the flower chambers, foraging again in the evening.

Nocturnal observations were not made. The dissections of flowers showed no immature stage

beyond larvae for any species and for Pseudophilothrips their red larvae were sometimes seen

on the trunks of the plants walking towards the soil, where they get buried to pupate. In the

other species thrips larvae just jumps from flowers to the soil in order to complete the

metamorphosis. Differently from the gregarious habit of Thripidae and Heterothripidae,

Pseudophilothrips was seen very often wandering alone on the buds, flowers, leaves and

branches and was very reticent to take flight, even when disturbed. Although no measures

were made, Pseudophilothrips individuals were two times larger than the other thrips species,

avoiding its entry in the flower chambers used by the other species as shelter.

TABLE 1. The values of frequency, constancy and dominance of thrips species in the five Malpighiaceae studied.

(

±1SD (N)); nS – number of flowers infested by thrips; % - frequency; C (Constancy index) – Ct=constant,

Ac=accessory, Acd=accidental; %D – percentage of the thrips species in relation to the total thrips found in the

plant; D-dominant; E-eudominant; D-dominant; Sd-subdominant; Ev-eventual; Rr-rare.

± 1SD (N)

nS % C %D D

Frankliniella condei 0.57±1.19 (86) 42 0.28 Ac 0.18 E

Frankliniella minuta 0.01±0.08 (1) 1 0.01 Acd 0.01 Ev

Frankliniella sp. 1 0.07±0.38 (10) 5 0.03 Acd 0.02 Sd

Scutothrips nudus 0.48±1.02 (72) 32 0.21 Acd 0.15 E

Heterothrips peixotoa 1.09±1.68 (163) 61 0.41 Ac 0.33 E

Heterothrips sp. 1 0.58±1.39 (87) 33 0.22 Acd 0.18 E

Heterothrips sp. 2 0.04±0.26 (6) 4 0.03 Acd 0.01 Ev

Heterothrips sp. 3 0.02±0.14 (3) 3 0.02 Acd 0.01 Ev

Heterothrips sp. 4 0.01±0.08 (1) 1 0.01 Acd 0.00 Rr

Pseudophilothrips sp. 1 0.07±0.35 (11) 8 0.05 Acd 0.02 Sd

Banisteriopsis malifolia

N. i 0.33±0.94 (109) 31 0.21 - 0.22 -

Frankliniella condei 0.47±1.47 (70) 17 0.11 Acd 0.06 D

Frankliniella sp. 1 0.12±0.65 (18) 7 0.05 Acd 0.02 Sd

Halmathrips sp. 0.01±0.08 (1) 1 0.01 Acd 0.00 Rr

Scutothrips nudus 0.05±0.28 (8) 6 0.04 Acd 0.01 Ev

Heterothrips peixotoa 8.51±6.96 (1276) 132 0.88 Ct 0.82 E

Heterothrips sp. 2 0.02±0.18 (3) 2 0.01 Acd 0.00 Rr

Heterothrips sp. 3 0.02±0.14 (3) 3 0.02 Acd 0.00 Rr

Heterothrips sp. 5 0.04±0.26 (6) 4 0.03 Acd 0.01 Ev

Pseudophilothrips sp. 2 0.58±1.71 (87) 25 0.17 Acd 0.08 D

Liothrips sp. 0.04±0.30 (6) 3 0.02 Acd 0.01 Ev

Peixotoa tomentosa

N. i 0.55±1.41 (83) 28 0.19 - 0.08 -

Frankliniella condei 0.83±2.09 (62) 13 0.17 Acd 0.07 D

Frankliniella schultzei 0.04±0.20 (3) 3 0.04 Acd 0.00 Rr

Frankliniella sp. 1 0.16±0.74 (12) 4 0.05 Acd 0.01 Ev

Lenkothrips sp. 0.01±0.12 (1) 1 0.01 Acd 0.00 Rr

Scutothrips nudus 1.20±2.16 (90) 22 0.29 Ac 0.10 D

Heterothrips peixotoa 8.21±6.57 (616) 50 67 Ct 0.71 E

Heterothrips sp. 3 0.04±0.26 (3) 2 0.03 Acd 0.00 Rr

Liothrips sp. 0.01±0.12 (1) 1 0.01 Acd 0.00 Rr

Pseudophilothrips sp. 3 0.35±0.85 (26) 14 0.19 Acd 0.03 Sd

Banisteriopsis laevifolia

N. i 0.83±2.09 (54) 18 0.24 - 0.06 -

Frankliniella condei 0.03±0.16 (4) 4 0.03 Acd 0.01 Ev

Frankliniella occidentalis 0.01±0.08 (1) 1 0.01 Acd 0.00 Rr

Frankliniella sp. 1 0.06±0.35 (9) 5 0.03 Acd 0.02 Sd

Lenkothrips sp. 0.02±0.14 (3) 3 0.02 Acd 0.01 Ev

Scutothrips nudus 0.07±0.46 (10) 5 0.03 Acd 0.02 Sd

Heterothrips peixotoa 2.27±4.42 (340) 59 0.39 Ac 0.83 E

Phlaeothripidae larvae 0.07±0.53 (11) 3 0.02 Acd 0.03 Sd

Byrsonima

intermedia

N. i 0.22±0.84 (33) 12 0.08 - 0.08 -

Frankliniella condei 0.65±1.29 (98) 43 0.29 Ac 0.21 E

Frankliniella sp. 1 0.31±0.81 (47) 25 0.17 Acd 0.10 D

Scutothrips nudus 0.19±0.76 (28) 10 0.07 Acd 0.06 Sd

Heterothrips peixotoa 1.74±2.23 (261) 84 0.56 Ct 0.56 E

Heterothrips sp. 1 0.14±0.59 (21) 10 0.07 Acd 0.04 Sd

Haplothrips gowdeyi 0.01±0.08 (1) 1 0.01 Acd 0.00 Rr

Phlaeothripidae larvae 0.03±0.41 (5) 1 0.01 Acd 0.01 Ev

Banisteriopsis

campestris

N. i 0.01±0.04 (6) 3 0.02 - 0.01 -

FIGURE 5. A) Heterothrips peixotoa feeding on pollen of Banisteriopsis malifolia; B) H. peixotoa between the

stamens of B. malifolia; C) Pseudophilothrips sp. 1 on a pre anthesis flower of B. malifolia; D) thrips under the

chambers of B. malifolia; E) H. peixotoa foraging on a petal of Peixotoa tometosa. Circles in the figures indicate

the position of thrips. (Photos by Estevão Alves-Silva).

In general thrips were most common during the dry season (H=231.84245; df=11;

p<0.0001), from June to October (FIGURE 6A). This pattern was in great part caused by the

abundance of the most profuse species in our study, H. peixotoa (H=235.38337; df=11; p<

0.0001). The FIGURE 6A shows that the pattern of occurrence of the total number of thrips

along the year was similar to that of H. peixotoa, (FIGURE 6B) but different from the other

abundant species like F. condei (H=70.64970; df=11; p<0.0001) (FIGURE 6C) and S. nudus

(H=56.34501; df=11; p<0.0001) (FIGURE 6D). The highest densities of these three species

are coincident with the flowering of P. tomentosa and B. laevifolia, as shown in the next

sections.

***

-2.0

1.4

4.8

8.2

11.6

15.0

M A M F

O N D JJ

2008 2009

-2.0

-1.4

4.8

11.6

15.0

8.2

Number of thrips individuals

-2

M A M F

O N D JJ

2008 2009

-2

Number of thrips individuals

-1

M A M F

O N D JJ

-1

2008 2009

Number of thrips individuals

-2

-1

M A M F

O N D JJ

-2

-1

2008 2009

Number of thrips individuals

FIGURE 6. Fluctuation of thrips along the year. A) Total number of thrips; B) Heterothrips peixotoa; C)

Frankliniella condei; D) Scutothrips nudus. *** means statistical differences (p<0.0001; Kruskall-Wallis test).

Lowercase letters upon the bars indicate significant statistical differences (p <0.0001, Dunn’s test for multiple

comparisons).

Other than thrips, ants and spiders were also found on the plants (FIGURE 7). Although

no counting was performed, the most frequent ants were Camponotus crassus (Mayr 1862)

(Formicinae: Formicidae) and Ectatomma tuberculatum (Olivier 1804) (Ectatomminae:

Formicidae) but some Pachycondyla villosa (Fabricius) (Ponerienae: Formicidae) were also

observed foraging on the plants sometimes. Both ants and spiders did not preyed on thrips and

at the time these predators were foraging thrips stayed concealed under the flower chambers.

The tiny entry of chambers allowed thrips to come and go but predators were too big to have

access to these structures.

Species richness estimated through Jacknife had a close value to that observed for the

plants indicating a good effort in thrips sampling (TABLE 2). Simpson index of diversity,

which is influenced by the importance of most dominant species, evidenced differences

between the plants. The elevated value of Simpson index together with the low evenness in

FIGURE 7. Potential predators of thrips in Malpighiaceae. A) Pachycondyla villosa on a branch of Peixotoa

tomentosa; B) Ectatoma tuberculatum on a leaf of P. tomentosa; C) Camponotus crassus on a flower of

Banisteriopsis malifolia; D) Oxyopidae spider on a flower of P. tomentosa; E) Salticidae spider on a fruit of B.

campestris; F) Thomisidae spider on a flower of P. tomentosa. (Photos by Estevão Alves-Silva).

P. tomentosa and Byrsonima intermedia resulted from the high abundance and frequency of H.

peixotoa revealing the existence of a dominant species.

TABLE 2. Thysanopterofauna analysis in the five Malpighiaceae species studied

Banisteriopsis

malifolia

Peixotoa

tomentosa

Banisteriopsis

laevifolia

Byrsonima

intermedia

Banisteriopsis

campestris

Flowers collected 150 150 75* 150 150

Species richness 10 10 9 7 7

Jackniffe 11.8 10.9 10.8 7.9 7.9

Shannon index 1.59 0.60 0.88 0.49 1.26

Simpson index 0.24 0.75 0.59 0.81 0.38

Species evenness 0.7 0.26 0.40 0.25 0.65

*This species presented smaller quantities of flowers to be sampled than other ones

According to the Shannon index, B. malifolia was the species with higher thrips diversity,

followed by B. campestris, B. laevifolia, P. tomentosa and Byrsonima intermedia,

respectively. The lowest value for Shannon index was observed in Byrsonima intermedia

since H. peixotoa accounted for 83% of the thrips individuals present. The same situation

occurred in P. tomentosa where the high abundance of H. peixotoa (82%) resulted in low

diversity. The balance between species richness/species diversity was registered B. malifolia

where the Simpson index was lower and species evenness higher.

The variation of environmental data can be seen in FIGURE 8. Linear multiple regression

showed that thrips were negatively related with relative humidity (R²=0.74, F

1,8

=7.402

p<0.05) but not with temperature and rainfall (FIGURE 9).

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb

Months

Number of thrips

0.0

5.0

10.0

15.0

20.0

25.0

30.0

Mean temperature ºC

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb

Months

Number of thrips

100

150

200

250

300

350

400

Rainfall (mm)

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb

Months

Number of thrips

Relative humidity %

Thrips

Rainfall

Humidity

Temperature

Number of thrips

Rainfall (mm)

Temperature ºC

Relative humidity %

Months

50 60 70 80

Relative humidity %

0.0

0.5

1.0

1.5

Thrips (Log)

y = 2.85 - 0.03x

50 60 70 80

Relative humidity %

0.0

0.5

1.0

1.5

Thrips (Log)

y = 2.85 - 0.03x

Phenological analysis (FIGURE 9), showed that the five Malpighiaceae species studied

presented sequential flowering, enabling thrips to find food and shelter in any of these species

along the year. P. tomentosa presented the largest flowering period while B. laevifolia had the

shortest. Low intensity of flowers was noted in B. campestris, as shown by the numbers inside

the circles in FIGURE 5. All plants presented high levels of seasonality (TABLE 3), denoted

by the elevated values of r, and the Rayleigh significance values of the mean angles (a). The

highest value of r was obtained in B. laevifolia, which flowers first appeared in August and

after a short boom in September, the plant ceased the flower production. The patterns of

FIGURE 8. Mean number of thrips found in

Malpighiaceae flowers through the time,

according to (A) rainfall (mm); (B)

temperature (ºC) and (C) relative humidity

(%)

FIGURE 9. Linear multiple regression

showed relation between thrips and relative

humidity. The number of thrips was log

transformed to fit in normal distribution

flowering based on frequency showed that these Malpighiaceae species presented annual and

intermediate flowering episodes, in a period varying from two (B. laevifolia) to four months

(P. tomentosa). The other three species bloomed for three months each.

January

February

March

April

May

JuneJuly

August

September

October

November

December

4 4

3 3

2 2

1 1

January

February

March

April

May

JuneJuly

August

September

October

November

December

4 4

3 3

2 2

1 1

January

February

March

April

May

JuneJuly

August

September

October

November

December

4 4

3 3

2 2

1 1

January

February

March

April

May

JuneJuly

August

September

October

November

December

4 4

3 3

2 2

1 1

January

February

March

April

May

JuneJuly

August

September

October

November

December

4 4

3 3

2 2

1 1

Byrsonima intermedia Banisteriopsis campestris

Banisteriopsis laevifolia

Banisteriopsis malifolia

Peixotoa tomentosa

FIGURE 9. Phenological data (Circular statistics analysis) of five Malpighiaceae species in the tropical savanna

of Uberlândia, MG, Brazil. The outside and bold curves (circular standard deviation) indicate the flowering

season of each species. Black bars and inside doted lines indicate the percent of flowers from 0 to 4; meaning

1=1–25%; 2=26–50%; 3=51–75% and 4=76–100% percent of flowers present.

TABLE 3. Results of circular statistic analyses tested for five Malpighiaceae species in the Tropical Savanna of

Uberlândia, MG, Brazil.

Phenological Variables

Banisteriopsis

malifolia

Peixotoa

tomentosa

Banisteriopsis

laevifolia

Byrsonima

intermedia

Banisteriopsis

campestris

Mean angle (a) 105° 182.374° 247.631° 323.794° 15°

Month of peak in

flowering

April July September November January

Circular standard

deviation

16.93° 25.88° 9.70° 19.24° 19.50°

Length of mean

vector (r)

0.96 0.90 0.99 0.95 0.94

Rayleigh test of

uniformity (P)

<0.01 <0.001 <0.01 <0.001 <0.05

All flowers present bilateral symmetry with five petals and sepals. Banisteriopsis

laevifolia, B. campestris and P. tomentosa flowers have eight oil glands under the sepals

while B. malifolia may have eight or 10 and Byrsonima intermedia contains 10 elaiophores.

Corolla is composed of five nail-shaped free petals. The limb is flat in all species except in

Byrsonima intermedia, which it is concave and the flowers born in great number in dense

inflorescences. In all plants the claw of the posterior "flag" petal is often conspicuously

thicker than the lateral petals. The most conspicuous differences among the flowers rely on

the color and the size (TABLE 4).

TABLE 4. Differences in flower color and size of the five Malpighiaceae species studied. Subscribed lowercase

letters indicate statistical significant differences in flower size.

Flower color

Flower diameter

± 1SD (N)

Kruskal-Wallis

Banisteriopsis malifolia Pink 2.6±0.14 (60)

Peixotoa tomenosa Yellow 4.11±0.15 (60)

Banisteriopsis laevifolia Yellow 1.64±0.13 (60)

Byrsnonima intermedia Yellow 1.6±0.06 (60)

Banisteriopsis campestris Pink 2.6±0.07 (60)

H=258.8708

Gl=4

p< 0.0001

Regarding the flower size and the abundance of thrips the curve adjustment technique

showed that linear regression was appropriate for all plants. Floral dimensions were positively

related with thrips abundance, thus the bigger was the flower diameter, more thrips could be

hosted inside it (FIGURE 10).

2.3

2.4

2.5

2.6

2.7

2.8

2.9

3.0

y = -37.8 + 16.1x

****

Flower diameter

Number of thripsNumber of thrips

2.4

2.5

2.6

2.7

2.8

Flower diameter

Number of thrips

****

y = -100 + 40.4x

1.4

1.5

1.6

1.7

1.8

Flower diameter

y = -18 +12.9x

1.4

1.5

1.6

1.7

1.8

1.9

2.0

Flower diameter

Number

thrips

****

y = -59.5 + 44x

3.7

3.8

3.9

4.0

4.1

4.2

4.3

4.4

4.5

Flower diameter

****

y = -123.9 + 32x

Flower diameter (cm)

Flower diameter (cm) Flower diameter (cm)

Flower diameter (cm)

Number of thrips

FIGURE 10. Linear regression between

flower size and thrips abundance in

Malpighiaceae species studied in the cerrado

vegetation: (A) Banisteriopsis malifolia

R²=0.42; F

1,58

=41.768; p<0.0001; (B)

Peixotoa tomentosa R²=0.70; F

1,58

=134.570;

p<0.0001; (C) Banisteriopsis laevifolia

R²=0.39; F

1,58

=36.429; p<0.0001; (D)

Byrsonima intermedia R²=0.12; F

1,58

=8.16;

p<0.01 and (E) Banisteriopsis campestris

R²=0.68; F

1,58

=120.52; p<0.0001.

6. DISCUSSION

This study showed that Brazilian Savannah Malpighiaceae supports a great diversity of

thrips (at least 19 species) and we present evidence that sequential flowering plays an

important role in the maintenance of this diversity. As a matter of fact, flowering plants and

insects are two of the major groups of living beings. The origin of flowering plants opened

new niches for insect diversification, which in turn may have driven plant speciation.

Alternatively, one group may have tracked the previous diversification of the other group

(Ehrlich & Raven 1964, Pellmyr 1992). In this context, sequential flowering is an important

natural resource to help in the survivorship and diversification of generalist species of

herbivores and/or pollinators (Bascompte & Jordano 2007). Relative to other host plants the

diversity and richness of thrips registered in this study is so far one of the most remarkable

features (see Pinent et al. 2005 for comparisons).

To a better comprehension on the importance of these plants in thrips ecology, and the

impact of these insects as floral herbivores in Brazilian Savanna vegetation, this discussion

will be divided in two parts. The first one will present a brief review of thrips species

recorded and its importance in a Brazilian context. The second part will discuss the ecological

implications of host plant preferences and seasonality in this thrips-Malpighiaceae

relationship.

6.1 Thrips occurrence and its importance: a brief review

6.1.1 Suborder Terebrantia

This suborder was the most representative and important to the study comprising over

95% of all the individuals analyzed occurring in all Malpighiaceae. Suborder Terebrantia

encompasses about 2400 species in eight families: Uzelothripidae, Merothripidae,

Melanthripidae, Aeolothripidae, Fauriellidae, Adiheterothripidae, Heterothripidae and

Thripidae (Mound & Morris 2007) and Brazil is represented by five of them: Uzelothripidae,

Merothripidae, Aeolothripidae, Heterothripidae and Thripidae. About one-third of the 700

species of thrips registered in Brazil are grouped in the suborder Terebrantia and about 22

species are considered to damage cultivated plants and five to transmit tospovirus (Monteiro

2002, Mound 2002a). Inventories in natural areas of Brazil revealed that Thripidae and

Heterothripidae are the most common families to be sampled (Pinent et al. 2006)and in our

study this pattern was maintained. Thripidae and Heterothripidae accounted for 14 species

and were responsible for the high levels of diversity. The Thripidae pests we found in our

study like Frankliniella schultzei and F. occidentalis were of low occurrence and not thought

to be causing notable damages to Malpighiaceae species.

Terebrantia members have the ovipositor well developed and saw-like, their wings are

usually covered with microtrichia and the fore wing presents ate least one longitudinal vein

reaching to apex (Richards & Davies 1988). The eggs are inserted below the plant cuticle,

into the tissue of the plant on which the female is feeding. Terebrantia has two pupal stages

(Mound & Marullo 1996). Individuals in this suborder have very wide habits, from fungus,

leaf and flower-feeding to predatory and ectoparasitic behavior habits (Grimaldi & Engel

2005, Alves-Silva & Del-Claro unpubl. data). In Malpighiaceae we presumed that all fed on

flower tissues and pollen, either because thrips lived on the flowers and also because fungus

were not registered.

Family Heterothripidae

Heterothripidae accounted for the most diversity in Terebrantia with eight species against

six from Thripidae. The high richness and diversity of Heterothripidae in all Malpighiaceae

studied shows that these plants are very important as major and/or minor hosts for thrips

maintenance along the year in Cerrado natural areas, particularly for H. peixotoa.

Heterothripidae is a family comprising over 70 species in four genera and it is usually

found in dicotyledons and only in the New World (Mound & Marullo 1996, Mound & Morris

2007). With one exception, all the species are flower-living. The exception, Aulacothrips

dictyotus Hood has been shown to be ectoparasitic on a species of Homoptera (Izzo et al.

2002) and also uses the membracids for phoresy (Alves-Silva & Del-Claro unpubl. data). Out

of the 71 species described in Heterothripidae, 64 belong in Heterothrips, however almost

nothing is known of the biology of the species (Mound & Marullo 1996). Available studies

reported the occurrence of Heterothripidae in only a few plants. Feller et al. (2002), observed

Heterothrips arisaemae Hood feeding on Arisaema triphyllum (L.) Schott. (Araceae) in

United States and this thrips was also implicated on pollination. In Brazil Heterothripidae was

found on flowers of Poaceae, Myrtaceae, Rubiaceae, Asteraceae (Pinent et al. 2005) and

Malpighiaceae (Del-Claro et al. 1997). In our study Heterothrips sp. 1 was very frequent in B.

malifolia, its major host but the other Heterothrips morphospecies were not representative.

The possibility that these Heterothrips morphs are new species is big, particularly for

Heterothrips sp 4. which possesses a pair of curved horns on the abdomen dorsally, an

anatomic feature never seen before.

Heterothrips peixotoa Del-Claro, Marullo and Mound 1997 – This was the most abundant

species in this study and its dominance in the plants was constant and regular all over the year.

All Malpighiaceae analyzed can be considered good hosts for H. peixotoa but population rates

reach its maximum on P. tomentosa and B. laevifolia, though the other plants serve as quite

good hosts as well, since adults and immatures were found simultaneously. Heterothrips

peixotoa was an undescribed species until 1997, when it was first discovered and studied in

the flowers of P. tomentosa coexisting with ants (Del-Claro et al. 1997). So far H. peixotoa

was registered only in Brazil and other than Malpighiaceae this species was recorded in

Eryngium sp. (Apiaceae) and Homolepis glutinosa (Sw.) F. Zuloaga & Soderstr. (Poaceae)

(Pinent et al. 2005).

Scutothrips nudus (Moulton, 1932) – This species was abundant in B. malifolia and B.

laevifolia which may be considered major hosts. In the other plants S. nudus occurrence was

low, blurred either by H. peixotoa as well as F. condei (Thripidae). Though its commonness

in B. malifolia and B. laevifolia, this thrips species was not seen foraging on the anthers and

petals like H. peixotoa and its habits remain unknown. In structure this genus is intermediate

between Aulacothrips and Heterothrips. Four South American species are currently placed in

this genus (Mound & Marullo 1996). No information is available of S. nudus biology or

ecology. In our study this species was present in all plants but the major hosts were B.

malifolia and B. laevifolia.

Lenkothrips sp. – There is not what to say about this species since only three individuals

were sampled in the flowers of Byrsonima intermedia. This taxon is recognized at generic

level because of anatomical remarkable features of the only included species (Mound &

Marullo 1996). No information about its host associations is available.

Family Thripidae

This family is, with 2060 known species, by far the largest of the Sub Order Terebrantia

(Mound & Morris 2007) but in this study the abundance of Thripidae individuals was exceed

by Heterothripidae members. The Thripidae is found worldwide, and includes almost all of

the pest species of thrips (Morse & Hoddle 2006) which were represented by F. condei, F.

schultzei and F. occidentalis in our study, but only F. condei was adundant whereas the other

two were represented by one individual each. The species of many genera are associated only

with grasses, whereas others are associated only with dicotyledonous plants, some in flowers

but others only on leaves (Mound 2002a). Pest species are commonly more adaptable in their

habits, and many of them feed and breed both on leaves and in flowers (Strauss & Karban

1994, Leite et al. 2006). There are no registers of the number of Thripidae species in Brazil,

however in the genera Frankliniella about 40 species have been recorded, 18 of them

described originally from this country (Monteiro 2002). This diversity is quite similar to

Costa Rica with 44 species (Mound & Marullo 1996). Frankliniella is a large genus of about

180 species, 90% of which are from the Neotropics; species recognition is peculiarly difficult

particularly amongst the small pale bodied forms (Mound & Marullo 1996).

Frankliniella condei John, 1928 – Among the Thripidae this species was the most abundant

occurring in all Malpighiaceae studied, its population was low only in Byrsonima intermedia

therefore not considered a host for F. condei. These individuals are very vagile and easily

come and go from flowers all day long. They often stayed under the flower chambers with

other co-specifics and went out to forage on the petals alone. The small size together with

pale-yellow color of individuals makes them hard to see on the flowers. Frankliniella condei

seems to be common and endemic to Brazil and it was already found in several plants both

mono and dicocotyledons in Santa Catarina, Minas Gerais and São Paulo States (Monteiro et

al. 2001). This species has economic importance by attacking nectarine (Prunus persica var.

nuscipersica (L.) Batsch) causing damage to flower’s ovarium and fruits (Hickel &

Ducroquet 1998, Pinent et al. 2008). Other registers include Rosa sp., Citrus aurantium L.,

Citrus limon (L.) Burm. f., Persea Americana Mill., Mangifera indica L., Zea mays L. and

Medicago sativa L. (Silveira et al. 2005). In Cerrado F. condei was found in the flowers of

Hancornia speciosa Gomez in high densities and coexisting with staphilinidae beetles.

Apparently there was no competition between these two taxa and while beetles fed on pollen

thrips fed on floral tissues (pers. obs). Natural enemies of F. condei are unknown (Silveira et

al. 2005).

Frankliniella minuta (Moulton) – The only one individual sampled in our study does not

permit us to state about its ecology and host associations and therefore we may not consider B.

malifolia as a host plant for F. minuta. By the way is the first register of this species on

Cerrado natural plants. Frankliniella minuta is a group of related species which were initially

thought to be pollinators of daisy flowers in United States (Annand 1926). Indeed Asteraceae

seems to be the main hosts for this group where they breed and feed (Mound & Marullo 1996).

Frankliniella minuta distribution seems to be restricted to Americas where it was registered

from United States to Peru (Mound & Marullo 1996, Kirk 2002). In Brazil, F. minuta had

been described based in a few specimens and the records were very doubtful (Monteiro 2002)

with no information about its host plants. Later samples brought out three species of minuta

group: F. bertelsi (De Santis, 1967), F. distinguenda Bagnall, 1919 and F. oxyura Bagnall,

1919, all of them common to Asteraceae (Pinent et al. 2005, Cavalleri et al. 2006).

Frankliniella schultzei (Trybom) – This was also a low occurrence thrips species with only

three individuals found on P. tomentosa. This polymorphic pollen feeding species is common

to South America and has been seen in large numbers in southern Brazil on cultivated flower

crops such as Chrysanthemum (Asteraceae) and Gladiolus (Iridaceae) (Mound & Marullo

1996). In Australia this species was recorded in eight natural plants in which Malvaviscus

arboreus Cav. (Malvaceae) was considered as F. schultzei main host (Milne & Walter 2000,

Milne et al. 2007). Although F. schultzei is sometimes considered a pest and a vector of

Tospovirus (Sakurai 2004), it is also known as a predator of mites in Australia (Mound &

Marullo 1996). Frankliniella schultzei, like F. occidentalis, does not seem to be specifically

adapted for preying on mite eggs, even though such predation enhances performance and

reproductive output of F. schultzei when constrained on leaves (Milne & Walter 2000). In

Brazil most studies on F. schultzei regards its association with crops and the transmission of

virus (Nagata & de Avila 2000, Monteiro et al. 2001) and its ecology and biology on Brazil

natural plants are unknown. The three individuals found in B. laevifolia are not representative

and this is not a major host F. schultzei.

Frankliniella occidentalis (Pergande) – Like F. minuta, F. occidentalis was represented by

only one individual and we may assume that no Malpighiaceae is a host for this species.

Known as western flower thrips, this polymorphic, polyphagous and omnivorous thrips is the

species which accounts for almost all of the published studies about these thrips. Such

importance is not surprising given that this species is a major worldwide pest of agricultural

and horticultural crops (Trichilo & Leigh 1986, Agrawal & Klein 2000, Morse & Hoddle

2006). The species causes considerable damage to a wide range of plants through feeding,

oviposition and transmission of tospoviruses, and the financial cost of this spread has been

enormous (Kirk & Terry 2003). Frankliniella occidentalis populations in crops are suppressed

by predators like Orius insidiosus (Say 1832) (Hemiptera: Anthocoridae) (Funderburk et al.

2000) or by the use of chemicals (Helyer & Brobyn 1992), however the vagility, high

reproduction rates and the intrinsic resistance of F. occidentalis to pesticides (Immaraju et al.

1992), makes this species difficult to control on integrated pest management programmes

(Gaum et al. 1994, Jensen 2000, Bielza 2008). In Brazil it has been registered in many plants

(Monteiro 2002). In Byrsonima intermedia its occurrence is rare and clearly this is not a host

for this thrips species.

Halmathrips (Demetriothrips) – One more species to join the group of one individual

sampled which does not permit assumptions about the ecology and host associations. So far,

five species have been described in this genus; but few individuals exist to compare. Because

so few specimens are available and because all of them are inadequately mounted for critical

study it is not possible to assess their taxonomic or systematic positions with any confidence

(Mound & Marullo 1996). In Brazil Halmathrips was found on the leaves of Casearia

decandra Jacq. (Flacourtiaceae) (Pinent et al. 2005). The subgenus Demetriothrips was

described by a single female from Mexico and no information about its ecology is available.

In Brazil this is the first register for this subgenus. They probably all feed on the leaves of

forest trees (Mound & Marullo 1996).

6.1.2 Sub Order Tubulifera, family Phlaeothripidae

The large individuals of suborder Tubulifera were well represented and if we take into

account that most species in this suborder are fungivorous, its occurrence in flowers of

Malpighiaceae is quite interesting. The suborder Tubulifera comprises the single and largest

family within Thysanoptera, the Phlaeothripidae with about 3500 described species (Mound

& Morris 2007). About two-thirds of the 700 species of thrips registered in Brazil are grouped

in the suborder Tubulifera and only two species are considered to damage cultivated plants

and none are known to be associated with any tospoviruses (Monteiro 2002, Mound 2002a).

This family exhibits a wide range of life styles, particularly fungus feeding and gall forming

(Mound & Marullo 1996). Members of this suborder have the ovipositor developed into a

chute, the wings have no microtrichia and the veins are absent or vestigial (Richards & Davies

1988). Eggs are usually deposited horizontally, but more rarely vertically on the leaf or other

surface on which the female is feeding. Tubuliferans have three pupal stages (Mound &

Marullo 1996).

Pseudophilothrips – Surprisingly each one of the three Malpighiaceae in which this genera

was found (B. malifolia, P. tomentosa and B. laevifolia) supports one different species of

Pseudophilothrips (Laurence Mound pers. comm.) which account for four species worldwide

(Mound & Marullo 1996). Malpighiaceae are host for Pseudophilothrips because both adult

and immature were found concomitant on the plant. This genus is known as leaf feeding and

responsible for high levels of herbivory on their hosts (Hight et al. 2002, Cuda et al. 2009 ).

The most remarkable case occurs in Schinus terebinthifolius Raddi, a native Anarcadiaceae

from Brazil (Manrique et al. 2008). Pseudophilothrips ichini (Hood), damage the plant with

their rasping-sucking mouthparts and frequently kill the new shoots. Because of this behavior,

P. ichini is being considered as a biological control agent for S. terebinthifolius in Florida,

where the past introduction of this plant is causing nowadays the loss of Florida natural

vegetation (Cuda et al. 2008).

Liothrips – The single individual found in P. tomentosa accounted for the high diversity of

thrips in this plant. This is one of the largest genera in the Thysanoptera with about 230

species (approximately 15 in Brazil), all leaf-feeding (Mound & Marullo 1996). In Hawaii

Liothrips urichi Karny is a biological control agent against the weed Clidemia hirta (L.) D.

Don (Melastomataceae) but predators like Pheidole megacephala (Fabricius) (Formicidae)

and Montandoniola moraguesi (Puton) (Anthocoridae) reduces thrips effectiveness in

controlling weed plants (Reimer 1988). In Brazil Varanda & Pais (2006) noted that Liothrips

didymopanacis Del-Claro & Mound (1996) was the main herbivore on Didymopanax vinosum

(Cham. & Schltdl.) Seem. (Apiaceae) throughout the year in Cerrado causing necrosis and

twisting of young leaves and these thrips were not affected by leaf defenses like the toughness

and tannins. Liothrips are also implicated with galls (Monteiro 2002). This genus was

registered in five plants in Southern Brazil (Pinent et al. 2005) and we showed that

Malpighiaceae is not a host for this thrips.

Haplothrips gowdeyi (Franklin 1908) – The single individual of this species was found in the

flowers of B. campestris. Unlike the dark color of Pseudophilothrips and Liothrips, H.

gowdeyi is brown in color and micropterous. This species is probably African in origin,

judging from its frequency in collections from that continent. However it is now widespread

around the tropics and one of the most common flower thrips in Caribbean (Mound &

Marullo 1996). In Brazil it was found coexisting with three species of Frankliniella in

chrysanthemum (Dendrathema grandiflora Tzvelev) crops in greenhouses (Carvalho et al.

2006) and it seems to be common for H. gowdeyi to be associated with other thrips species,

particularly Frankliniella (Annadurai & Velayudhan 1986). In nectarine (Prunus persica var.

nuscipersica (L.) Batsch) H. gowdeyi, together with other thrips, was responsible for causing

damage to flower’s ovarium and fruits (Hickel & Ducroquet 1998, Pinent et al. 2008); In

maize the predator Orius insidiosus (Say) was found positively associated with H. gowdeyi

and other two thrips species (Silveira et al. 2005). The significance of this co-occurence of H.

gowdeyi with other thrips species was not analyzed and deserves further attention.

6.2 Thrips community and host plant preferences

Studies of thrips communities are very rare and usually researchers focus on only one or a

few species of thrips (Agrawal et al. 1999, Seal et al. 2006), the exception accounting for pest

thrips in crops where more than one species is involved (see Carvalho et al. 2006, Dreistadt et

al. 2007). In an inventory conducted in Southern Brazil, Pinent et al. (2005) found three

coexisting thrips species in Banisteriopsis metallicolor (A. Juss.) O Donell & Lourteig.

(Malpighiaceae) and most diversity occurred in Asteraceae, recognizably to host several

thrips species (Mound 2005). Furthermore in Pinent et al. (2005) the only Malpighiaceae

present, from 72 plants analyzed, was B. metallicolor which hosted three species of thrips.

This contrasts with our findings in the present study since the least number of thrips species

found in a Malpighiaceae was six and the maximum was ten species, indicating the great

importance of these plants in Brazilian Savanna as pool of thrips diversity, relative to other

biomes.

The coexistence of many thrips species in a same microhabitat is quite common and may

involve portioning or resources like food, shelter and places to oviposit (Hickel & Ducroquet

1998, Pulliam 2000, Sakai 2001, Silveira et al. 2005, Pinent et al. 2008). Malpighiaceae

flowers are a homogeneous habitat; their flowers are very similar either in structure as in food

resources offered for thrips like pollen and floral tissues (Del-Claro et al. 1997). The ways in

which species within ecological communities partition available resources among themselves

is a major determinant of the diversity of coexisting species. All else being equal, a

community with more resource sharing, or greater niche overlap, will clearly support more

species than one with less niche overlap (Pianka 1974).

Heterothrips peixotoa was the most abundant thrips in all plants and may be considered

the species to make the best use of Malpighiaceae flowers, being a stronger competitor

relative to other species. Generally in communities of thrips, species of the genus

Frankliniella are the most abundant accounting in some cases for more than 90% of the

species sampled (Pearsall & Myers 2001, Carvalho et al. 2006) demonstrating either a good

adaptation to its habitat, high reproductive rates and better invasive and competitive behavior

than the other species (Morse & Hoddle 2006). However, in Malpighiaceae the situation is

opposite; H. peixotoa was the main herbivore in relation to the other thrips in all

Malpighiaceae studied, its dominance was constant and not exceeded by any other species.

Usually the dominance of species varies over time so allowing many species to coexist. Cho

et al. (2000) studied the spatial and temporal occurrence of three thrips species on tomato and

concluded that thrips shared the same space on the plants (upper and lower plant strata) but on

foliage, the thrips feeding resources, Frankliniella fusca (Hinds) was predominant while few

F. triciti (Fitch) and F. occidentalis were observed. This dominance changed as the season

progressed and F. occidentalis became dominant one month later.

Most cases of interspecific competition are indirect interactions between species mediated

by the influence of one species in the limiting resources of another species (Pulliam 2000). In

relation to reproduction, by avoiding sites already crowded with eggs of H. peixotoa, females

of other species might be forced to oviposit on other plants or in resources of lower nutritional

quality for their offspring thus bringing about a density-dependent regulation of population

size (Jaenike 1990).

In Malpighiaceae, except for H. peixotoa, the dominance of thrips species changed over

time depending on the plant, and the causes may be in the ecology and host ranges of the

species. For instance, F. condei was well represented in all plants except in Byrsonima

intermedia. This plant flowers in October in the beginning of the rainy season in the same

occasion that Hancornia speciosa Gomez (Apocynaceae) starts blooming. This Apocynaceae

is a major host of F. condei and large populations are found within its flowers until January,

when flower production ceases (Alves-Silva & Del-Claro unpul data). Moreover F. condei

was also found in abundance in Tocoyena formosa (Schum. & Schlecht) Schum (Rubiaceae)

and Himatanthus obovatus (Müll. Arg.) Woodson (Apocynaceae) (pers. obs). All these

species share the similarity of large white flowers with long tubular corolla and presence of

scent. The low numbers F. condei in Byrsonima intermedia may be explained by the high

invasive and the potential of this thrips to occupy new available microhabitats. Such statement

was corroborated by the fact that in B. campestris, the following plant in the chain of

Malpighiaceae sequential flowering, F. condei was abundant as at this period the other host

plants mentioned above do not produce flowers. Changes in host plants may be important in

determining which plant an insect will or will not choose. The simplest but perhaps most

common reason why certain plants are not preferred by a given herbivore may be related to

phenologies (Barbosa 1988). The overlapping of flowering between Byrsonima intermedia

and H. speciosa and the preference of F. condei for the latter is a reflection of the thrips

species lifestyle, a specific response to a specific set of selective forces. Frankliniella condei

host changing puts Malpighiaceae as major hosts in part of the year and minor hosts in other.

Also, in this context Malpighiaceae has a significant importance in the maintenance of species

such as F. condei which change their hosts according the availability of other resources in

time and space.

6.3 Resource and predators

Apparently Heterothrips species in Malpighiaceae are also common in other parts of the

world. In Costa Rica several species of Heterothrips were found in the flowers of common

Byrsonima and other species of Malpighiaceae (Mound & Marullo 1996). The conservative

aspect of floral morphology in all Malpighiaceae, with five petals and sepals forming a

chamber, may have profound implications on thrips occupation in the flowers. For example,

to leaf-mining or bud-boring insects, plant anatomy rather than plant phytochemistry or

phylogenetic relationships may determine host range (Powell 1980). Not only H. peixotoa,

but all thrips species may benefit of living under the sepal chambers. This microhabitat offers

escape from predators and also protection against environment (Del-Claro et al. 1997, Mound

& Terry 2001) indicating that both bottom-up and top-down forces are important in

structuring thrips communities (see Hunter & Price 1992). There is a wide acceptance that

thrips populations are limited by bottom-up forces (food or resource) (Mound 2005) but

enemy free space may be also a selecting force to make Malpighiaceae suitable for thrips

living.

In field observations Pseudophilothrips were the species most susceptible to predation. In

some occasions Pseudophilothrips stayed for long periods on the petals and its contrasting

dark color on this surface was very conspicuous. It could either expose the individuals to

predators as well as provoke desiccation through direct sun exposition. However no predator

attack to these thrips was observed and desiccation presumably did not take place because

these thrips species possesses a tough cuticle which may minimize the effects of sunlight and

heat. The most likely predators, jumping and crab spiders, did not spend their efforts on

Pseudophilothrips, possibly because thrips are low rewarding resources (Charnov 1976, Pyke

et al. 1977) or because their long setae along the body are defense mechanisms against

predators, the same strategy used by caterpillars (see Hare & Eisner 1993). Observations

indicated that predators played a negligible role in controlling all thrips populations, not only

Pseudophilothrips. Natural enemies of thrips are not well known and besides some Hemiptera

and Hymenoptera (Dreistadt et al. 2007) in crops and greenhouses little is known about thrips

predators in natural ecosystems.

According to Morse & Hoddle (2006) most resident natural enemies that attack thrips are

generalist predators and even those which presents some degree of specificity, such as

hymenopteran parasitoids that attack thrips eggs, (Megaphragma spp.) (Steyn et al. 1993,

Bernardo & Viggiani 2002, Tamo et al. 2002) and larvae (Ceranisus spp.: Eulophidae)

(Castineiras et al. 1996) generally inflict low levels of mortality (Hessein & Mcmurtry 1988).

But the most likely factor affecting the susceptibility to natural enemies is the life cycle of

thrips. Usually, eggs are laid inside plant tissues; there are two free-living larval instars; two

or three pupal stages that pupate within protective cracks on branches or in soil, buried

beneath the host plants; and winged vagile adults (Mound & Marullo 1996). Under such

conditions, a guild of generalist natural enemies would need to be simultaneously available in

several distinct habitats (e.g., arboreal to attack thrips larvae and adults exposed on leaves,

and subterranean to attack pupal stages in the soil) to minimize the number of life stages

benefiting from refuge in natural enemy free space. In addition, the “boom and bust” ecology,

patchy distribution of high-density populations, and occurrence of life stages that occupy

widely varied niches make invasive thrips an unstable resource for resident natural enemies

(Morse & Hoddle 2006). Obrist et al. (2005) have shown that pupal and prepupal thrips,

which are restricted in their mobility, were killed most successfully by Chrysoperla carnea

(Stephens) (Neuroptera: Chrysopidae) whereas older larvae and winged adults were more

likely to escape the attacks of predator and caught less successfully.

The behavior of both predator and prey is a crucial factor influencing predation and in

Malpighiaceae. The fluctuation of thrips populations along the year, the movements between

plants, the concealed habitats under the sepals, the small size and the flying-at-any-

disturbance behavior of these insects makes them hard to find and to capture by predators.

Parasitoids of thrips are species-specific (Triapitsyn 2005) and to succeed in Malpighiaceae,

parasitoids would have to be able to enter the tiny chambers where thrips live and be lucky to

find the certain species to parasitize, like the genera Frankliniella and Thrips (Tagashira &

Hirose 2001) but our observations showed no other arthropod species than thrips inside

flower chambers. The last but not less important to be mentioned is the defensive behavior of

some thrips in the form of anal exudates or volatile unpleasant odors (Tschuch et al. 2002).

In Malpighiaceae ants are the main predators of thrips and Fernandes et al. (2005) showed

that in Byrsonima crassifolia (Linnaeus) H. B. K. (Malpighiaceae) ants exerted strong

influences on the structure, composition, and dynamics of phytophagous insect communities,

including thrips, diminishing the damages of these insects through the herbivory (see Del-

Claro et al. 2006). Ants observed in our study were too big to enter the flower chambers to

prey on thrips and foraged rather on the leaves in order to get the nectar from extrafloral

nectaries. The impact of natural enemies may favor host specialization in phytophagous

insects but as a single host does not produce flowers all along the year, thrips are forced to

look for other flowering plants. The similarity between habitats may facilitate the occupation

because previous learning may maximize the use of this new habitat and save energy which

otherwise would be spent to know and explore this new habitat (Jaenike 1990). Therefore the

conservative aspect of flowering Malpighiaceae is so important either in providing food as

well as enemy free spaces (Del-Claro et al. 1997). So it is common to find so many thrips and

often the same species in sequential flowering Malpighiaceae.

6.4 Polyphagy

Sequential flowering Malpighiaceae offer a predictable and useful microhabitat for thrips

maintenance along the year because the different plants bloom in a series that allow thrips to

migrate between hosts where it can find food and protection. However, not all species of

thrips migrate from plants. Of all the thrips species common to the five Malpighiaceae, only

H. peixotoa abundantly infested all plant species, while Frankliniella condei and Scutothrips

nudus also occurred in all plants, but in low abundance sometimes.

The higher H. peixotoa abundancy shows that this species is able to feed and develop

successfully on all five plant species, suggesting that it is a Malpighiaceae generalist

herbivore. Peixotoa tomentosa and B. laevifolia presented the higher rates of H. peixotoa

infestation, indicating that these two plants are the major hosts while the other three plants are

placed as minor ones. The other thrips species in which the approach major/minor hosts are

suitable were F. condei and S. nudus since adult and immature of these species occurred in all

plants. Their indexes of dominance shows that for F. condei its major hosts were

Banisteriopsis malifolia and B. campestris while for S. nudus the major host was B. malifolia.

All these three thrips species may be considered polyphagous as herbivorous species tend to

have this designation simply on the basis of incidence records from numerous plant species

(Zalucki et al. 1986). Polyphagy is a main ecological feature for these thrips because it allows

the migration from plants whenever there are resources available so population can persist in

time and space in a variety of hosts. In this view, sequential flowering Malpighiaceae serve as

a predictable reservoir of food in which thrips may continue to make use of, independently of

the flowering species. This statement is according to Mound & Teulon (1995) who consider

polyphagous organisms to evolve local 'preferences' to suite local plant species availability.

That may be the reason why we found great diversity of thrips in Brazilian Savanna

Malpighiaceae and thrips are so successful in exploring these plants.

According to Milne & Walter (2000) polyphagy in thrips represents a survival mechanism

against periodic stressful conditions but may also mean an adaptation for a species to exploit a

diversity of sporadically and unpredictable abundant hosts opportunistically. Such an

adaptation can be considered a functional equivalent of the other mechanisms used by various

thrips species to span unfavorable periods, namely aestivation and diapause (Ananthakrishnan

1993, Van Houten et al. 1995, Nakao 1998). Thrips in our study breed throughout the year

and do not overwinter so Neotropical sequential flowering provides habitats and food so

thrips do not need to enter the diapause.

6.5 Seasonality and phenology

Despite its uniqueness, thrips movements and maintenance in different seasons along the

year has not caught the attention of thysanopetorologists and there are few data available on it.

The first and most time consuming study was conducted by Davidson & Andrewartha (1948)

who recorded Thrips imaginis Bagnall, 1926, population during 14 years in two varieties of

roses in Australia. They concluded that thrips populations come and go from flowers more or

less in waves and this may be due to inherent gregariousness of the species. Also, the species

were more common in the localities where flowers were abundant and were highly influenced

by weather; the population was high in summer and low in winter. Relations with rain,

moisture and temperature were considered to increase thrips populations. More recently Leite

et al. (2002) did not observe relation between Scirtothrips manihoti Bondar, 1924 population

on cassava (Manihot esculenta Crantz var. Cacau) with rainfall, temperature and relative

humidity. Thrips populations were rather controlled by senescence of the plant and predators

than environmental factors. On Brassica oleracea L. var. acephala, Thrips tabaci Lind.

populations tended to increase as the mean temperature increased while heavy rain and high

humidity were deleterious to these insects (Leite et al. 2005). In Prunus persica var.

nuscipersica (L.) Batsch thrips are associated with years of dry winter (Hickel & Ducroquet

1998). In Brazilian Savannah thrips were related negatively with relative humidity. However,

since we analyzed five different host plants thrips might be related primarily with a particular

host and not with the climate solely. Data shows that both climate and host are apparently

responsible for thrips population rates given that thrips were more abundant in P. tomentosa

and B. laevifolia. These plants flowers in wet season when the rains are rare and relative

humidity is low. In cerrado vegetation rains may be a strong force reducing small herbivores

abundance (Del-Claro & Oliveira 2000).

6.6 The importance of sequential flowering and major hosts

Since a high proportion of plants expend their reproductive energy in single brief annual

pulses, the animal community dependent on flower resources can be expected to follow the

cyclicity of flowering and be reduced during the intervening periods, like pollinators such as

bees, butterflies and also thrips attracted to their foraging plants (Appanah 1993, Mound &

Terry 2001). For instance, in temperate zone the staggered annual flowering, instead the

sequential flowering, seems to be common. It comprises a progression of annual population

patterns in a sequence of species that extends for only part of the year. For example, in a

lowland tropical forest at La Selva, Costa Rica, beetle pollinated species flower in a staggered

sequence for part of the year (Young 1986). During the non flowering interval or gap the

beetles are dormant (Newstrom et al. 1994). Marquis & Braker (1994) discussed that in

tropical forests host plant seasonality is one of the main forces structuring the herbivores

communities. In the present study, the seasonal variation and sequential flowering of

Malpighiaceae followed by thrips species migration suggest that it is also applicable in the

tropical savannas.

In Neotropics sequential flowering is common (Frankie et al. 1974, Machado & Semir

2006, Marques & Lemos Filho 2008) and considering the level of competition for pollinators

during a general flowering the sequential flowering noted so far among trees with close floral

affinity may be a much more widespread phenomenon (Appanah 1993). As the five

Malpighiaceae in this study are sympatric and flowers are very similar, competition for

pollinators would be expected if the species bloomed at the same time. Competitive plant

effects will commonly occur when a shared pollinator forages so as to transfer pollen

interspecifically, since this will reduce the availabilities of effective pollinator movements,

pollen, and stigmatic surfaces to individuals of both species and may thereby limit their

reproductive output. Such effects will occur even if each plant species has additional

pollinators not shared by the other (Waser 1978). The timing of plant reproductive cycles

affects plant–plant interactions such as competition for resources or for pollinators (Newstrom

et al. 1994). This competition for pollinators has often been suggested as the primary selective

force molding flowering schedules (Brody 1997). For associated animal community,

sequential flowering plants represent a predictable and continuous source of resources

(Siqueira Filho & Machado 2001). Again, our data suggest that not only plant-pollinator

system is influenced by phenology and seasonality, but also plant-herbivore relationships.

Thrips have the capacity to increase their populations rapidly in response to the

availability of a massive source of flowers (Bawa & Hadley 1990). Mixed continual flowering

patterns have dramatic influence on amplitude peaks of thrips. This pattern has been described

for thrips pollinated species in Malaysia. After many years of sporadic light flowering, a

staggered but slightly sequential flowering of six Shorea (Dipterocarpaceae) species burst into

full, high intensity flowering. At this time, the short-lived thrips pollinators had an

exponential population explosion (Chan 1981, Appanah 1985). Shorea species are thrips

major hosts and at other times, when these hosts are not available, other species that flower

more frequently at low or intermediate amplitudes maintain the thrips at low population levels

(Appanah 1985, Bawa & Hadley 1990, Newstrom et al. 1994). Malpighiaceae also present the

same features as Shorea species such as increasing thrips populations and serve as major hosts

for some thrips species, but unlike Shorea which flowers only in part of the year, the

sequential flowering Malpighiaceae provides habitats for thrips maintenance during the entire

year. Moreover, the destination of Shorea thrips in the gaps of flowering is unknown whereas

for Brazilian savanna Malpighiaceae at least for H. peixotoa, F. condei, S. nudus their

whereabouts are known.

Davidson & Andrewartha (1948) noted that Thrips imaginis Bagnall populations

presented annual fluctuations related to availability of host plants. During the spring, fields

and gardens harbored flowering plants which provided favorable situations for T. imaginis.

During the summer these plants disappeared and the insects died almost completely. The

survivors were to be found in restricted local situations scattered thinly throughout the area of

distribution of the species, in minor hosts. Therefore major hosts are an essential and limiting

factor in maintaining thrips populations and have direct and undoubted implications for

conservation efforts in areas where the flora is endangered like Cerrado in Central Brazil

(Myers et al. 2000). The group of five sequential flowering Malpighiaceae analyzed in this

study has not been found elsewhere in plant inventories in cerrado vegetation. Usually these

inventories are made in protected reserves and accomplish mostly trees excluding shrubs and

vines from analysis and the Malpighiaceae eventually sampled, are mostly Byrsonima (Silva

et al. 2002, Assunção & Felfili 2004). It is really surprising the fact that Banisteriopsis and

Peixotoa are so rare in other Cerrado areas (Urso-Guimarães & Scareli-Santos 2006) as in

ours these plants are so abundant. Cerrado biota is not homogeneous, so additional

distribution data for different groups of organisms must be collected and organized in a

retrievable way to help conservationists to determine whether there are additional unidentified

subareas of endemism (Silva & Bates 2002 ).

If thrips, particularly H. peixotoa, are dependent of sequential flowering to maintain its

population along the seasons, the lack of any plant may have strong consequences because

thrips would be at least two months without host and thrips adult life span is about one month

(Murai & Loomans 2001). The register of this thrips species in plants other than

Malpighiaceae (Pinent et al. 2005) suggests wider habit exploitation. Also it has been argued

that polyphagy should favor risk spreading, with females laying their eggs on many host

plants in order to ensure that at least some offspring survive. Such a strategy, if beneficial,

could lead to the acceptance of a greater variety of host species for oviposition (Jaenike 1990)

and thrips could survive in small number in these minor hosts in the lack of the major ones.

The fact that some species matter more than others becomes especially clear in the case of

keystone species which refers to species whose loss has a disproportionate impact on the

community when compared to the loss of other species (Mills et al. 1993). We still cannot

assume Malpighiaceae as keystone species for thrips given that no large scale samplings were

made in other plants to compare. Yet most ecosystem processes are driven by the combined

biological activities of many species, and it is often not possible to determine the relative

contributions of individual species to ecosystem processes (Loreau et al. 2001, Naeem 2002,

Hooper et al. 2005). However our results and our knowledge of thrips occurrence so far,

particularly H. peixotoa, allow us to propose that the community of these sequential flowering

plants have a significant and noteworthy role in thrips time and space maintenance.

It would be useful to learn how thrips community would adapt itself to a change in its

staple food resources through availability in time and space. Would the diversity of potential

food species be a factor determining whether thrips could remain, feeding on substitutes, or

whether they would have to move to other habitats or plants? This approach will be the aim of

future studies and may elucidate different aspects of thrips biology and ecology and enrich

our knowledge about these minute and ubiquitous insects.

7 CONCLUSION

In this study we showed that sequential flowering Malpighiaceae has an important role in

the maintenance of thrips community throughout the year, especially for H. peixotoa, the most

abundant species in all samplings. The richness and diversity recorded is the highest ever

sampled for thrips living in a group of related taxonomic plants, possibly because the

conservative aspect of Malpighiaceae flowers provide food resources and protection against

predators. Large flowers support more thrips and the environment may be as important as the

plant flowering phenology in maintaining thrips in time and space. Future studies will attain

on the damages or benefits of thrips in their hosts as well as their occurrence on other

common plants on Brazilian Savanna vegetation.

Acknowledgements: Dr. Laurence A. Mound for the indentification of thrips and insightufull contribution on the

boardless knowledge of thrips worldwide; Ms. Adriano Cavalleri for the help in some aspects of Brazilian thrips;

Msc. Andrea Andrade Vilela for the fieldwork companion; Msc. Pietro Kiyoshi Maruyama Mendonça for

comments on the manuscript; Programa de Pós Graduação em Ecologia e Conservação de Recursos Naturais,

UFU and Capes (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for the finnancial support.

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