AVIAN VOCALIZATIONS AND PHYLOGENETIC SIGNAL

The difficulty of separating genetic and ecological components of voca lizations has discouraged biologists from using vocal characters to re construct phylogenetic and ecological history. By considering the phys ics of vocalizations in terms of habitat structure, we predict which o f five vocal characters of herons are most likely to be influenced by ecology and which by phylogeny, and test this prediction against a mol ecular-based phylogeny. The characters most subject to ecological conv ergence, and thus of least phylogenetic value, are first peak-energy f requency and frequency range, because sound penetration through vegeta tion depends largely on frequency. The most phylogenetically informati ve characters are number of syllables, syllable structure, and fundame ntal frequency, because these are more reflective of behavior and syri ngeal structure. Continued study of the physical principles that disti nguish between potentially informative and convergent vocal characters and general patterns of homology in such characters should lead to wi der use of vocalizations in the study of evolutionary history.