SuppReading2 - Vol 448 | 9 August 2007 |...

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LETTERS Host specificity of Lepidoptera in tropical and temperate forests L. A. Dyer 1 , M. S. Singer 2 , J. T. Lill 3 , J. O. Stireman 4 , G. L. Gentry 1 , R. J. Marquis 5 , R. E. Ricklefs 5 , H. F. Greeney 6 , D. L. Wagner 7 , H. C. Morais 8 , I. R. Diniz 8 , T. A. Kursar 9,10 9,10 For numerous taxa, species richness is much higher in tropical than in temperate zone habitats 1 . A major challenge in community ecology and evolutionary biogeography is to reveal the mechan- isms 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 6 Sto55 6 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 b 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. Ecological theory requires that organisms differ in their use of shared, limiting resources if they are to coexist. The role of resource specialization in fostering biodiversity is thus a central issue in eco- logy and evolutionary biology. A longstanding hypothesis predicts a direct relationship between ecological specialization and species rich- ness in communities 2 . Specialization reduces interspecific competi- tion and facilitates species coexistence by partitioning niche space 3,4 . Character divergence across generations in response to trophic inter- actions or competition 5 provides an evolutionary mechanism by which species richness and specialization can increase together 6–8 . Beginning with observations recounted by Darwin 9 and Wallace 10 , examples of ecological specialization in tropical organisms have fos- tered a widespread perception that specificity of interactions is a hallmark of the high-diversity tropics.
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This note was uploaded on 09/01/2011 for the course BIEB 128 taught by Professor Holway during the Fall '08 term at UCSD.

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SuppReading2 - Vol 448 | 9 August 2007 |...

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