May 29 2013

12:00 LSB 2320

Kevin Burns
Department of Biology, San Diego State University

Diversification of tanagers, the largest radiation of Neotropical songbirds


The tanagers represent a major continental radiation, making up an important component of the Neotropical fauna. Traditionally, the group was considered to contain 242 species of mostly colorful, fruit-eating or omnivorous birds. In this study, we show that the tanagers are a clade of 370 species spanning a diversity of feeding morphologies, plumage variation, vocal abilities, and habitat preferences. We reconstructed a phylogeny for tanagers using two mtDNA and four nuclear genes using a combination of maximum likelihood and Bayesian methods. Within tanagers, we identified 13 major clades that diverged at roughly the same time, but vary in size from 2 to over 100 species. These clades provide independent tests concerning character variation and species diversification. Compared to related groups of birds, the tanagers are significantly species-rich relative to background expectations, with a diversification rate comparable to Hawaiian silverswords. The phylogenetic tree of tanagers shows a pattern of lineage diversification expected under a scenario of adaptive radiation. Testing the fit of different diversification process models on an ultra metric tree identified an exponential density-dependent decline model as the most appropriate for tanagers. However, testing diversification models for each of the major clades of tanagers indicates that two of the major clades fit a pure birth model (the Darwin’s finch clade and the Sporophila clade). Using the phylogeny of tanagers, we also compare patterns of evolution in characters typically associated with natural selection (ecological niche, morphology) and those associated with sexual selection (plumage, song) and evaluate their relationship to diversification rates.















































































































































































































































































































































































































































































































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