A comparison of evolutionary rates between songs and calls in South-American Fire-eyes (Aves: Pyriglena): a hypotheses test in a phylogenetic framework

Abstract

Investigations on the concerted variation of multiple characters throughout the range of a taxa are fundamental for an understanding of evolutionary forces underlying the process of geographic divergence. In this project, the evolution of vocalizations will be studied in detail across the geographic range of South American Fire-eyes (Aves, Genus Pyriglena) in a phylogenetic framework. The Fire-eyes are members of a highly diverse but poorly studied assemblage of Neotropical birds, the Suboscine passerines. More specifically, it is proposed here to test hypotheses that could explain the patterns of variation among different vocal traits. It is proposed to contrast evolutionary patterns between songs and calls of Fire-eyes. In birds of the Thamnophilidae family, in which Fire-eyes are included, it is suggested that vocalizations are hard-wired and that songs have the primary dual function of mate attraction and territory defence whereas calls have the primary function of, for exemple, contact betweem pair members. Thus, one can infer that songs and calls are respectively long and short range acoustic signals and that natural and social and sexual selection would have a stronger influence on patterns of song evolution while calls would be more prone to the effects of genetic drift. Two predictions can be derived: 1) calls will track phylogeny more closely than songs and 2) songs will present a higher evolutionary rate than calls. (AU)