Ecology and morphology as drivers of passerine song differentiation across an island archipelago

Abstract

We conducted an integrative analysis to explore possible explanations for the song differentiation in bird populations from the mainland and the Tres Marías Archipelago (TMA) on the central-western Pacific coast of Mexico. We first analysed the effect of isolation on cultural transmission by comparing repertoire size and genetic fixation in four phylogenetically distantly related passerines for which previous studies have documented significant genetic divergence between island and mainland populations. Then, we examined the contributions of potential factors involved in song differentiation (syllable duration and frequencies, frequency range), including morphology (bill size and body weight), genetic divergence and environmental factors (precipitation and temperature). Syllable sharing between TMA and mainland populations was higher for Northern Cardinals Cardinalis cardinalis and Golden Vireos Vireo hypochryseus but lower for Rufous-backed Thrushes Turdus rufopalliatus. Songs of TMA populations showed longer syllable duration in Rufous-backed Thrush and Golden Vireo, and shorter syllable duration in Northern Cardinal than those on the mainland. No significant differences were found between island and mainland populations of Streak-backed Oriole Icterus pustulatus. Bill volume differed significantly between TMA and mainland populations of Northern Cardinals and Rufous-backed Thrushes but not Streak-backed Orioles and/or Golden Vireos. Correlations between body size and song frequencies were low but significant for most variables. We conclude that bird song differentiation on these islands is driven by isolation, environmental factors and morphology.

Marcelo Araya-Salas

Research Associate

My research interests include evolutionary behavioral ecology, cultural evolution, scientific programming and all possible combinations of them.