DOI: 10.5061/dryad.n7832
title: Data from: Darker where cold and wet: Australian birds follow their own version of Gloger's rule

description: Gloger's rule is usually interpreted as predicting darker coloured
 animals in warmer and more humid/vegetated regions. The relative
 importance of temperature and rainfall or vegetation is however unclear,
 and often only one variable is tested at a time, mainly through proxies.
 Here, I assess the predictions of Gloger's rule for interspecific
 achromatic plumage variation (dark to light variation) for an entire
 avifauna (551 species of Australian landbirds). I tested the effects of
 climatic variables (temperature and rainfall) and vegetation structure on
 plumage reflectance at species and assemblage level (100x100 km cells),
 controlling for phylogenetic relatedness and spatial autocorrelation. To
 assess the robustness of these results I compared observed results with
 those of a null distribution of effects obtained from repeatedly
 simulating random plumage reflectance evolution on the phylogeny. At both
 the species and assemblage level, darker coloured birds were found in
 wetter and colder regions and in more densely vegetated habitats.
 Simulations confirm results at the species level and the effect of
 temperature at the assemblage level, but rainfall and vegetation effects
 at the assemblage level fall within the distribution of simulated effects
 and should be interpreted with care. Interspecific colour variation in
 Australian birds supports Gloger's rule for rainfall/vegetation, but
 shows the opposite pattern for temperature. Darker colours in wet and
 vegetated environments are consistent with the role of melanin
 pigmentation in preventing feather degradation by bacteria, but also with
 background-matching for camouflage. Darker plumage might be beneficial in
 colder regions or detrimental in warmer regions if it affects
 thermoregulation, a selective force often only assumed to be of importance
 for ectotherms. The data highlight the need to test the generality of
 biogeographic rules across levels and at broad scale. Experimental work is
 needed to confirm the mechanisms linking plumage achromatic variation to
 climate.
description: Data for species-level
 analysesData includes the
 following variables: phylo.name=scientific names which match nomenclature
 used in birdtree.org; patch.loc= dorsal (d) or ventral (v);
 log10av.ref=log10-transformed average reflectance of dorsal or verntral
 plumage patches; hab.close=index of vegetation density; temp=average
 temperature based on the distribution of the species; log10rain=average
 log10-transformed annual rainfall based on the distribution of the
 species; lat=average latitude based on the distribution of the species;
 lon=average longitude based on the distribution of the species; sex=male
 or female.species.level.data.csvData for the assemblage-level analysesData has the following variables: cell.name=identifier for each 1 degree cell; n.species=number of species recorded in cell; av.ref.m.d= average male dorsal reflectance value for species recorded in cell; av.ref.m.v=average male ventral reflectance value for species recorded in cell; av.ref.f.d=average female dorsal reflectance value for species recorded in cell; av.ref.f.v=average female ventral reflectance value for species recorded in cell; Lat=latitude of centre of cell; Lon=longitude of centre of cell; n.surveys=number of surveys carried out in cell; temp=average temperature in a 50 km radius around the centre of cell; log10rain=log10-transformed average annual rainfall in a 50 km radius around the centre ; veg=average vegetation structure score in a 50 km radius around the centre of cell.assemblage.level.data.csv