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Influencia diferencial de la expresión de Slc7a11 y la condición corporal sobre la pigmentación producida por feomelanina en dos poblaciones de trepador azul Sitta europea con diferente riesgo de depredación

The expression of the gene Slc7a11 promotes the antioxidant capacity of cells by providing them with cysteine that can be used for the synthesis of glutathione (GSH), the most important intracellular antioxidant. In melanocytes, intracellular cysteine can also enter melanosomes and get incorporated in the pigment pheomelanin synthesis pathway, thus decreasing cysteine availability for GSH synthesis and potentially creating chronic oxidative stress. Therefore, this study hypothesized that a mechanism limiting the use of intramelanocytic cysteine for pheomelanin synthesis in environmental conditions generating oxidative stress may be physiologically advantageous and favored by natural selection. Evidence we searched of such a mechanism by comparing the influence of melanocytic Slc7a11 expression on pheomelanin?based pigmentation in developing Eurasian nuthatch Sitta europaea nestlings from two populations differing in predation risk, a natural source of oxidative stress. Pheomelanin synthesis and pigmentation tended to increase with Slc7a11 expression in the low?risk population as expected from the activity of this gene, but decreased with Slc7a11 expression in the high?risk population. The same was not observed in the expression of five other genes influencing pheomelanin synthesis without affecting cysteine availability in melanocytes. The influence of body condition on the intensity of pheomelanin?based pigmentation also differed between populations, being positive in the low?risk population and negative in the high?risk population. The resulting pigmentation of birds was more intense in the high?risk population. These findings suggest that birds perceiving high predation risk may limit the use of cysteine for pheomelanin synthesis, which becomes independent of Slc7a11 expression. Some birds may have thus evolved the ability to adjust their pigmentation phenotype to environmental stress. informacion[at] Galván & Sanz (2020) Differential influence of Slc7a11 expression and body condition on pheomelanin-based pigmentation in two Eurasian nuthatch Sitta europaea populations with different predation risk. J Avian Biol DOI 10.1111/jav.02275
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Females mate with males with diminished pheomelanin-based coloration in the Eurasian nuthatch Sitta europaea

Females mate with males with diminished pheomelanin-based coloration in the Eurasian nuthatch Sitta europaea

Sexual selection can drive the evolution of phenotypic traits because of female preferences for exaggerated trait expression in males. Sexual selection can also lead to the evolutionary loss of traits, a process to which female preferences for diminished male trait expression are hypothesized to contribute. However, empirical evidence of female preferences for diminished male traits is virtually lacking. Eurasian nuthatches Sitta europaea provide an opportunity to test this possibility, as a chestnut flank patch produced by the pigment pheomelanin is present since the first plumage of these birds and its color is more intense in nestlings in poor condition in our study population. It has been proposed that developing birds in poor condition may increase their production of pheomelanin as a detoxifying strategy. Female nuthatches may thus prefer mating with males showing flank feathers of diminished color, as this could indicate that males experienced good conditions early in development, which can positively affect the fitness of future generations. Here results according with this prediction in a wild population of Eurasian nuthatches are shown, as adult males with lighter chestnut feathers paired earlier in the season, while chestnut coloration had no effect on female mating success. Chestnut color expression was not affected by the body condition of birds, suggesting that females obtain information on the body condition in early life of their potential mates and not on their current body condition. This constitutes one of the few examples of females mating with males showing diminished traits and provides the only explanation so far by which this process can occur. informacion[at] Galvan & Rodríguez-Martinez (2018) Females mate with males with diminished pheomelanin?based coloration in the Eurasian nuthatch Sitta europaea. J Avian Biol. Doi 10.1111/jav.01854