Friday, August 8, 2008

PS 85-142: A macro-ecological analysis of tree-caterpillar interactions

Ellen C. Thompson and Andrew J. Kerkhoff. Kenyon College


The interactions between herbivores and their host plants provide a useful system for the study of large-scale patterns of biodiversity. In this study, we are interested in determining whether herbivores and their host plants exhibit tight coevolutionary relationships, or whether herbivores employ a more opportunistic strategy when colonizing hosts. Using a macroecological approach, we examined the phylogenetic and biogeographic associations between Lepidoptera and a sample community of 36 eastern deciduous tree species. Specifically, we examine how patterns of host range overlap, phylogenetic relatedness and functional similarity are related to the taxonomic and phylogenetic similarity of herbivore communities. Results/Conclusions

A total of 645 macrolepidoptera were recorded as herbivores on our 36 host species, with almost 1,500 pairwise interactions. The diversity of herbivore assemblages varied greatly, and we found that closely related hosts have more similar and more phylogenetically related Lepidoptera communities. However, the pattern decays as host phylogenetic distance increases. These data, together with the fact that phylogenetic clustering of herbivore communities appears in fully a quarter of the host taxa, suggest that coevolution occurs against a background of more diffuse, opportunistic interactions. The opportunistic nature of herbivores is supported by the fact that herbivore community similarity was positively correlated with host range overlap. This suggests that, as opportunists, herbivores are more likely to colonize more apparent hosts. Overall, our study raises interesting questions about long-held hypotheses regarding the origin and maintenance of biodiversity, and illuminates the need for greater sampling of Lepidopteran communities even in relatively well-surveyed temperate forest ecosystems.