1. Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, Louisiana 70118, USA
2. Department of Biology, Wesleyan University, Middletown, Connecticut 06459, USA
3. Department of Biological Sciences, George Washington University, Washington, DC 20052, USA
4. Department of Biological Sciences, Wright State University, Dayton, Ohio 45435, USA
5. Department of Biology, University of Missouri–St Louis, St Louis, Missouri 63121, USA
6. Yanayacu Biological Station and Center for Creative Studies, Cosanga, Napo, Ecuador c/o Foch 721 y Juan Leon Mera, Quito, Ecuador
7. Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, Connecticut 06269, USA
8. Department of Ecology/Zoology, University of Brasilia, 70910-900, Brasilia, DF, Brazil
9. Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840, USA
10. Smithsonian Tropical Research Institute, Panama City, Panama

Correspondence to: L. A. Dyer¹ Correspondence and requests for materials should be addressed to L.A.D. (Email: ldyer@tulane.edu).

Abstract

For numerous taxa, species richness is much higher in tropical than in temperate zone habitats¹. A major challenge in community ecology and evolutionary biogeography is to reveal the mechanisms underlying these differences. For herbivorous insects, one such mechanism leading to an increased number of species in a given locale could be increased ecological specialization, resulting in a greater proportion of insect species occupying narrow niches within a community. We tested this hypothesis by comparing host specialization in larval Lepidoptera (moths and butterflies) at eight different New World forest sites ranging in latitude from 15° S to 55° N. Here we show that larval diets of tropical Lepidoptera are more specialized than those of their temperate forest counterparts: tropical species on average feed on fewer plant species, genera and families than do temperate caterpillars. This result holds true whether calculated per lepidopteran family or for a caterpillar assemblage as a whole. As a result, there is greater turnover in caterpillar species composition (greater diversity) between tree species in tropical faunas than in temperate faunas. We suggest that greater specialization in tropical faunas is the result of differences in trophic interactions; for example, there are more distinct plant secondary chemical profiles from one tree species to the next in tropical forests than in temperate forests as well as more diverse and chronic pressures from natural enemy communities.

1. Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, Louisiana 70118, USA
2. Department of Biology, Wesleyan University, Middletown, Connecticut 06459, USA
3. Department of Biological Sciences, George Washington University, Washington, DC 20052, USA
4. Department of Biological Sciences, Wright State University, Dayton, Ohio 45435, USA
5. Department of Biology, University of Missouri–St Louis, St Louis, Missouri 63121, USA
6. Yanayacu Biological Station and Center for Creative Studies, Cosanga, Napo, Ecuador c/o Foch 721 y Juan Leon Mera, Quito, Ecuador
7. Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, Connecticut 06269, USA
8. Department of Ecology/Zoology, University of Brasilia, 70910-900, Brasilia, DF, Brazil
9. Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840, USA
10. Smithsonian Tropical Research Institute, Panama City, Panama

Correspondence to: L. A. Dyer¹ Correspondence and requests for materials should be addressed to L.A.D. (Email: ldyer@tulane.edu).

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