Widespread convergent morphological evolution within the largest family of songbirds

Abstract

Although convergence is a common evolutionary phenomenon, few studies have quantified its prevalence across a large, densely sampled clade. Large-scale phylogenies and the advent of novel computational methods facilitate more robust identification of convergent events and their statistical significance. The tanagers (Aves: Thraupidae), the largest family of songbirds, offer an excellent opportunity to study the extent of phenotypic convergence in response to similar ecological pressures on a continental scale. To investigate convergence in the group, we used the largest phylogenetic and multivariate morphological dataset to date for the clade. First, we used phylogenetic comparative analyses to show a correlation between diet and aspects of bill shape. We then investigated our dataset for the presence and magnitude of convergent events and assessed significance through simulations and modeling analyses. Overall, we found that around half (45.3%) of species and clades we tested have converged in morphological space more than would be expected by chance alone. Our study shows that across Thraupidae, various bill shapes have evolved convergently to fill multiple distinct sections of ecological niche space, reflecting a signal of ecological opportunity and structural constraints.

Keywords: Thraupidae; convergence; diet guild; evolution; morphology; tanagers.