Urbanisation as a potential environmental filter to the plumage colours of passerines

Abstract

Urban ecosystems can act as an environmental filter that only allows the establishment of species with specific life-history traits. These environmental filters can result in the homogenization of biological diversity. Understanding what traits set apart the animals able to colonize and establish in urban habitats from those who cannot is a crucial step towards understanding how organisms respond to urbanization, and what subset of biodiversity can be supported by urban environments. In this present project, I will combine citizen data, phylogenetic comparative methods, and a continuous measure of urbanization to investigate if urbanization is acting as an environment filter across passerine species on one of the largest cities in the Americas, Sao Paulo. Specifically, I will focus on bird plumage color, a trait that is shaped by the combined strengths of natural and sexual selection. I have two specific questions: 1) what is the relationship between urbanization and passerine plumage color diversity? The predation risk of colorful birds can increase with urbanization and the diversity of carotenoid resources responsible for bird plumage color can decay with urbanization. So, I hypothesize that birds with homogeneous coloration can have more success in highly urbanized areas. In this way, I expect to find a negative relationship between urbanization and diversity of plumage colors of passerines. 2) what is the relationship between urbanization and sexual dichromatism of passerine plumage? In urban areas, plumage sexual dichromatism could be reduced by dietary constraints and increased predation. So, I expect to find a negative association between urbanization and the presence of passerine bird species showing sexual plumage dichromatism which, in turn, would imply that species sorting associated with urbanization operates by a complex interplay between dietary constraints and the evolutionary outcome of sexual selection. (AU)