Corticosterone regulates multiple colour traits in Lacerta [Zootoca] vivipara males

Abstract

Ornamental colours usually evolve as honest signals of quality, which is supported by the fact that they frequently depend on individual condition. It has generally been suggested that some, but not all types of ornamental colours are condition dependent, indicating that different evolutionary mechanisms underlie the evolution of multiple types of ornamental colours even when these are exhibited by the same species. Stress hormones, which negatively affect condition, have been shown to affect colour traits based on different pigments and structures, suggesting that they mediate condition dependence of multiple ornament types both among and within individuals. However, studies investigating effects of stress hormones on different ornament types within individuals are lacking, and thus, evidence for this hypothesis is scant. Here, we investigated whether corticosterone mediates condition dependence of multiple ornaments by manipulating corticosterone levels and body condition (via food availability) using a two-factorial design and by assessing their effect on multiple colour traits in male common lizards. Corticosterone negatively affected ventral melanin-and carotenoid-based coloration, whereas food availability did not affect coloration, despite its significant effect on body condition. The corticosterone effect on melanin-and carotenoid-based coloration demonstrates the condition dependence of both ornaments. Moreover, corticosterone affected ventral coloration and had no effect on the nonsexually selected dorsal coloration, showing specific effects of corticosterone on ornamental ventral colours. This suggests that corticosterone simultaneously mediates condition dependence of multiple colour traits and that it therefore accounts for covariation among them, which may influence their evolution via correlational selection.

Stress‐induced changes in color expression mediated by iridophores in a polymorphic lizard

“…The increase in overall throat luminance following stress manipulation is consistent with results found in birds (Almasi, Roulin, Jenni‐Eiermann, & Jenni, ; Roulin et al., ), butterflies (Kemp & Rutowski, ), and other lizard species (San‐Jose & Fitze, ). The magnitude of change in achromatic contrast for corticosterone‐treated individuals in our study was around 6 JNDs, suggesting that lizards are likely to be able to perceive the observed variation.…”

“…Consequently, color signals may be reliable indicators of an individual's condition and ability to tolerate stress. Evidence for this hypothesis derives from experiments showing that an increase in glucocorticoids can affect the size and intensity of sexually selected color signals (Fitze et al., ; Kemp & Rutowski, ; Kemp, Vukusic, & Rutowski, ; Lendvai, Bókony, Angelier, Chastel, & Sol, ; Roulin et al., ; Saino et al., ; San‐Jose & Fitze, ; San‐Jose, Granado‐Lorencio, Sinervo, & Fitze, ; Steffen & McGraw, ). However, whether stress affects processes of pigment production and/or deposition, the structural properties of cells and tissues, or both is largely unknown.…”

“…For example, changes in the spacing of platelets rapidly produce color change in tree lizards (Morrison et al., ) and chameleons (Teyssier et al., ). Furthermore, in common lizards ( Lacerta vivipara ), corticosterone manipulation affects carotenoid‐based color expression by altering iridophore‐mediated “background reflectance,” but not carotenoid deposition in the skin (San‐Jose & Fitze, ).…”

Corticosterone: a costly mediator of signal honesty in sand lizards

“…CORT has direct and largely negative effects on color production (Calisi and Hews ; San‐Jose and Fitze ; Weiss et al. ) and, in particular, interferes with the process of melanogenesis through competitive binding of the melanocortin receptor necessary for melanin pigmentation (Ducrest et al.…”

Condition‐dependence, pleiotropy and the handicap principle of sexual selection in melanin‐based colouration

“…We implanted nestling barn owls with pellets releasing the hormone corticosterone, which is implicated in behavioural and physiological responses to environmental stress. Although the administration of corticosterone can lead to a decrease in melanin‐based colouration (see also San José & Fitze, ), inter‐individual variations in colouration observed in the barn owl are due largely to genes rather than environmental factors (Roulin et al ., ). Therefore, in the barn owl covariation between melanin‐based colouration and the regulation of corticosterone is not due to corticosterone altering melanogenesis, but rather to genes involved in melanogenesis pleiotropically altering the regulation of corticosterone (Almasi et al ., ).…”