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Testing the simple and complex versions of Gloger’s rule in the Variable Antshrike (Thamnophilus caerulescens, Thamnophilidae)

Citation

Marcondes, Rafael (2021), Testing the simple and complex versions of Gloger’s rule in the Variable Antshrike (Thamnophilus caerulescens, Thamnophilidae), Dryad, Dataset, https://doi.org/10.5061/dryad.xpnvx0kbw

Abstract

Gloger’s rule is a classic ecogeographical principle that, in its simplest version, predicts animals should be darker in warmer and wetter climates. In a rarely-tested more complex version, it also predicts animals should be more rufous in warmer and drier climates. The Variable Antshrike is a widely-distributed South American passerine that presents an impressive amount of plumage color variation and occupies a wide variety of climatic conditions. Moreover, genetic and vocal evidence indicate ongoing hybridization in south-central Bolivia among three populations with very distinct plumages. We collected color data from 232 specimens from throughout this species’ distribution to test the predictions of Gloger’s rule. We found a negative correlation between brightness and precipitation, consistent with the simple version of Gloger’s rule. In contrast, we found that birds were darker in cooler climates, contrary to the simple version of Gloger’s rule, but consistent with recent findings in other taxa. We found support for both predictions of complex Gloger’s rule and suggest it might be driven by background matching. We conclude by concurring with a recent suggestion that the simple version of Gloger’s rule should be reformulated exclusively in terms of humidity.

Methods

One file (.rds) includes raw reflectance spectra generated with used an OceanOptics USB2000 spectrophotometer coupled to an OceanOptics PX-2 pulsed xenon light source. The other file (.csv) includes specimen information, brightness and redness variables calculated from those spectra (as dsecribed in the associated manuscript), and climatic data from the CHELSA database.

Usage Notes

The .rds file contains a single R object of  'rspec' class. (see specifications here: https://cran.r-project.org/web/packages/pavo/pavo.pdf). This object can be manipulated and further processed with functions available in the R package ‘pavo’.

Funding

National Science Foundation, Award: DEB-1146265

Conselho Nacional de Desenvolvimento Científico e Tecnológico, Award: 201234/2014-9