Complex Plumage Patterns Can Be Produced Only with the Contribution of Melanins.

Ismael Galván,Juan J Negro,Jorge García-Campa

doi:10.1086/693962

Ismael Galván, Juan J Negro + Show 1 more

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https://doi.org/10.1086/693962

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Abstract

Birds exhibit an extraordinary diversity of plumage pigmentation patterns. It has been overlooked, however, that complex patterns can be produced only with the contribution of melanins because these are the only pigments under direct cellular control. We tested this hypothesis for the first time examining the plumage patterning of all species of extant birds. Thirty-two percent of species show complex plumage patterns, the vast majority (98%) including the contribution of colors produced by melanins. Only 53 species show complex patterns that do not contain melanin-based colors, and these species display unusual colorations and belong to three families where innovative metabolic modifications of conventional carotenoid pigments have been described. While the adaptive functions of complex plumage patterns remain poorly understood and in most cases are ascribed to fulfill camouflage, our findings indicate that such functions will be understood only by considering the synthesis pathway of melanins.

Highlights

Attempts to explain the extraordinary diversity in animal pigmentation across species have been made since the beginning of stud-The evolution of pigmentation patterns may be better understood by the mechanisms of color production, as these determine the physiological constraints that lead to natural selection’s favoring or limiting different color types (Galván and Solano 2009)
We postulate a largely overlooked observation regarding plumage patterns: they are apparently produced by colors conferred by melanins but not by colors conferred by carotenoids (McGraw 2006), nanostructures (Maia et al 2011), or the group-specific pigments such as psittacofulvins, turacin, or porphyrins (Galván et al 2016)
This difference is key for understanding the pressures that allow or constrain the development of plumage patterns, as while carotenoids are photosynthetic pigments that birds obtain from dietary sources and are transported with lipoproteins through the bloodstream to the follicles of growing feathers (McGraw 2006), melanins are endogenously synthesized in specialized cells

Summary

Introduction

The evolution of pigmentation patterns may be better understood by the mechanisms of color production, as these determine the physiological constraints that lead to natural selection’s favoring or limiting different color types (Galván and Solano 2009). We postulate a largely overlooked observation regarding plumage patterns: they are apparently produced by colors conferred by melanins (for a description of colors produced by natural melanins, see Galván and Wakamatsu 2016) but not by colors conferred by carotenoids (McGraw 2006), nanostructures (Maia et al 2011), or the group-specific pigments such as psittacofulvins, turacin, or porphyrins (Galván et al 2016) This difference is key for understanding the pressures that allow or constrain the development of plumage patterns, as while carotenoids are photosynthetic pigments that birds obtain from dietary sources and are transported with lipoproteins through the bloodstream to the follicles of growing feathers (McGraw 2006), melanins are endogenously synthesized in specialized cells (i.e., melanocytes; Lin et al 2013). Our aim here is to test, by examining the appearance of all species of extant birds, the hypothesis that complex plumage patterns are produced only with the contribution of melanin-based pigmentation

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