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Pteridine pigments compensate for environmental availability of carotenoids
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  • Devi Stuart-Fox,
  • Katrina Rankin,
  • Adrian Lutz,
  • Adam Elliott,
  • Andrew Hugall,
  • Claire McLean,
  • Iliana Medina
Devi Stuart-Fox
University of Melbourne School of BioSciences
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Katrina Rankin
The University of Melbourne
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Adrian Lutz
The University of Melbourne
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Adam Elliott
The University of Melbourne
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Andrew Hugall
Museums Victoria
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Claire McLean
Museums Victoria
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Iliana Medina
University of Melbourne School of BioSciences
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Abstract

Carotenoid-based colours are a textbook example of honest signalling because carotenoids must be acquired from the environment. However, many species produce similar colours using self-synthesised pteridine pigments. A compelling but untested hypothesis is that pteridines compensate for low environmental availability of carotenoids because it is metabolically cheaper to synthesise pteridines than to acquire and sequester carotenoids. Based on a phylogenetic comparative analysis of 11 pigment concentrations in skin tissue of agamid lizards, we show that pteridine concentrations are higher and carotenoid concentrations lower in less productive environments. Both carotenoid and pteridine pigments were present in all species, but only pteridine concentrations explained colour variation among species. Furthermore, pigment concentrations were uncorrelated with indices of sexual selection. These results suggest that variation among species in pteridine synthesis compensates for environmental availability of carotenoids and challenge the paradigm of honest carotenoid signalling in vertebrates with complex colour production mechanisms.