Correlated evolution of morphology and vocal signal structure in Darwin's finches.

:Speciation in many animal taxa is catalysed by the evolutionary diversification of mating signals. According to classical theories of speciation, mating signals diversify, in part, as an incidental byproduct of adaptation by natural selection to divergent ecologies, although empirical evidence in support of this hypothesis has been limited. Here I show, in Darwin's finches of the Galápagos Islands, that diversification of beak morphology and body size has shaped patterns of vocal signal evolution, such that birds with large beaks and body sizes have evolved songs with comparatively low rates of syllable repetition and narrow frequency bandwidths. The converse is true for small birds. Patterns of correlated evolution among morphology and song are consistent with the hypothesis that beak morphology constrains vocal evolution, with different beak morphologies differentially limiting a bird's ability to modulate vocal tract configurations during song production. These data illustrate how morphological adaptation may drive signal evolution and reproductive isolation, and furthermore identify a possible cause for rapid speciation in Darwin's finches.

Podos J 《NATURE》

Ecological adaptation and species recognition drives vocal evolution in neotropical suboscine birds.

Seddon N 《EVOLUTION》

Correlated evolution of beak morphology and song in the neotropical woodcreeper radiation.

Mating signals may diversify as a byproduct of morphological adaptation to different foraging niches, potentially driving speciation. Although many studies have focused on the direct influence of ecological and sexual selection on signal divergence, the role of indirect mechanisms remains poorly understood. Using phenotypic and molecular datasets, we explored the interplay between morphological and vocal evolution in an avian radiation characterized by dramatic beak variation, the Neotropical woodcreepers (Dendrocolaptinae). We found evidence of a trade-off between the rate of repetition of song syllables and frequency bandwidth: slow paced songs had either narrow or wide frequency bandwidths, and bandwidth decreased as song pace increased. This bounded phenotypic space for song structure supports the hypothesis that passerine birds face a motor constraint during song production. Diversification of acoustic characters within this bounded space was correlated with diversification of beak morphology. In particular, species with larger beaks produced slower songs with narrower frequency bandwidths, suggesting that ecological selection on beak morphology influences the diversification of woodcreeper songs. Because songs in turn mediate mate choice and species recognition in birds, these results indicate a broader role for ecology in avian diversification.

Derryberry EP ，Seddon N ，Claramunt S ，Tobias JA ，Baker A ，Aleixo A ，Brumfield RT ... -  《-》

The calmodulin pathway and evolution of elongated beak morphology in Darwin's finches.

Abzhanov A ，Kuo WP ，Hartmann C ，Grant BR ，Grant PR ，Tabin CJ ... -  《-》

Vocal mechanics in Darwin's finches: correlation of beak gape and song frequency.

Podos J ，Southall JA ，Rossi-Santos MR 《JOURNAL OF EXPERIMENTAL BIOLOGY》