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Previous issue date: 2015-03-19 === Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES === the factors that influence the choice of egg-laying sites by adult insects is
critical in order to identify the major drivers of host-plant use by insects. The abundance
of different plant species and the level of feeding specialization of insects have been
considered as determinants of the preferential use of host-plants by herbivorous insects.
We analyzed the host use patterns of endophagous insects that feed on Asteraceae
flower-heads to test the following hypotheses: (i) the abundance of a plant species has a
positive effect on the preference of herbivorous insects for that plant species, and (ii) the
relative importance of plant abundance in determining preferential use is greater for
herbivorous species that use a wider range of host-plant species. We used data on the
interactions between herbivorous insects and Asteraceae host-plants family sampled in
20 Cerrado areas in São Paulo State. We analyzed 11 species of endophagous insects
and 12 host-plant species. For eight species of herbivorous insects, plant species
abundance showed a positive influence on herbivore preference. Three insect species
did not respond to any influence of plant abundance on feeding preferences, but one of
them showed a positive effect of plant species identity. Furthermore, both the most
specialized and the most generalist insect species presented a stronger positive effect of
plant species abundance in their choice of a host-plant. Therefore, our study shows that
the abundance of plant species is a major factor determining the preferential use of hostplants
by the endophagous insects of Asteraceae. Moreover, we show that herbivore diet
breadth mediates the relationship between host use and plant abundance. === Estudos abordando interações entre insetos herbívoros e plantas hospedeiras
abrangem uma vasta gama de aspectos ecológicos. Boa parte desses aspectos pode ser
relacionada diretamente ou indiretamente com a alta dependência que os herbívoros
apresentam em relação às suas plantas hospedeiras. Devido a essa alta dependência os insetos
herbívoros respondem tanto à riqueza e densidade, quanto ao arranjo espacial das hospedeiras
no habitat (Wright and Samways 1999, Summerville and Crist 2001, Tsharntke and Brandl
2004). Além das plantas hospedeiras proporcionarem recurso alimentar para os insetos, elas
também fornecem abrigo e microclima adequado para o desenvolvimento dos imaturos
(Gaston et al. 1992). Insetos herbívoros não consomem indiscriminadamente as plantas,
havendo geralmente alguma preferência por poucas espécies de plantas hospedeiras (Futuyma
and Gould 1979). Assim, mudanças, por exemplo, em aspectos quantitativo e qualitativo,
nessas hospedeiras podem ter grandes efeitos sobre as populações desses herbívoros. Nesse
contexto, pode-se dizer que a amplitude da dieta é um componente fundamental do nicho das
espécies de insetos herbívoros, influenciando desde sua dinâmica populacional e
suscetibilidade à extinção (Brown 1984), até sua distribuição geográfica (Strong et al. 1984).
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