Examining the link between relaxed predation and bird coloration on islands

Abstract

Insular ecosystems share analogous ecological conditions, leading to patterns of convergent evolution that are collectively termed as the 'island syndrome'. In birds, part of this syndrome is a tendency for a duller plumage, possibly as a result of relaxed sexual selection. Despite this global pattern, some insular species display a more colourful plumage than their mainland relatives, but why this occurs has remained unexplained. Here, we examine the hypothesis that these cases of increased plumage coloration on islands could arise through a relaxation of predation pressure. We used comparative analyses to investigate whether average insular richness of raptors of suitable mass influences the plumage colourfulness and brightness across 110 pairs of insular endemic species and their closest mainland relatives. As predicted, we find a likely negative relationship between insular coloration and insular predation while controlling for mainland predation and coloration, suggesting that species were more likely to become more colourful as the number of insular predators decreased. By contrast, plumage brightness was not influenced by predation pressure. Relaxation from predation, together with drift, might thus be a key mechanism of species phenotypic responses to insularity.

Keywords

insularity; colour volume; comparative analysis; plumage coloration; signal evolution

Published in

Biology Letters
2020, Volume: 16, number: 4
Publisher: ROYAL SOC

SLU Authors

• Paquet, Matthieu

  • Department of Ecology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Evolutionary Biology
Ecology


Publication identifier

DOI: https://doi.org/10.1098/rsbl.2020.0002

Permanent link to this page (URI)

https://res.slu.se/id/publ/105639