Plumage coloration follows Gloger’s rule in a ring species

Aim: Animal coloration is expected to differ between populations in different habitats according to Gloger’s rule, with darker animals found in more humid, vegetated or warmer environments. Yet despite considerable support across the globe, the mechanisms behind this biogeographical rule are currently still unclear. Exploiting a ring species with plumage coloration from crimson to pale yellow, we test Gloger’s rule and the mechanisms behind phenotypic divergence. Location: South-eastern Australia. Major taxa studied: Crimson rosellas (Platycercus elegans). Methods: We combined three modelling approaches (spatial regression; random decision forest species distribution and conditional inference tree) to test the association between 10 environmental variables (based on long-term climate data and remotely sensed reflectance of the land) and plumage coloration across the distribution of P. elegans. We also took in-situ measurements of background coloration of dominant vegetation to examin...