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

• Published in: Nature (London) Vol. 409; no. 6817; pp. 185 - 188
• Main Author: Podos, Jeffrey
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 11.01.2001; Nature Publishing Group
• Subjects: Adaptation, Physiological; Animal communication; Animals; Beak - anatomy & histology; Biological and medical sciences; Biological Evolution; Birds; Body Constitution; Body size; Ecuador, Galapagos Is; Evolution; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; Geospiza; Male; Phylogeny; Sexual Behavior, Animal; Songbirds - anatomy & histology; Songbirds - physiology; Speciation; Vocalization, Animal; Galapagos Islands; Pacific Ocean Islands; Ecuador, Galapagos Is; Vocal tract; Mating call; Correlation; Sound production; Biological evolution; Phylogeny; Vertebrata; Beak; Song; Morphology; Body size; Aves; Speciation
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/35051570

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.