Abstract
Sexual selection and social selection are two important theories proposed for explaining the evolution of colorful ornamental traits in animals. Understanding signal honesty requires studying how environmental and physiological factors during development influence the showy nature of sexual and social ornaments. We experimentally manipulated physiological stress and immunity status during the molt in adult king penguins (Aptenodytes patagonicus), and studied the consequences of our treatments on colourful ornaments (yellow‐orange and UV beak spots and yellow‐orange auricular feather patches) known to be used in sexual and social contexts in this species. Whereas some ornamental features showed strong condition‐dependence (yellow auricular feather chroma, yellow and UV chroma of the beak), others were condition‐independent and remained highly correlated before and after the molt (auricular patch size and beak UV hue). Our study provides a rare examination of the links between ornament determinism and selection processes in the wild. We highlight the coexistence of ornaments costly to produce that may be honest signals used in mate choice, and ornaments for which honesty may be enforced by social mediation or rely on genetic constraints.
Highlights
Understanding the evolution of conspicuous ornaments, often costly to produce and maintain, has been a long-standing focus of evolutionary biology (Andersson, 1994; Kuijper, Pen, & Weissing, 2012). Darwin (1871) laid the groundwork for this topic by observing that conspicuous ornaments could enhance access to sexual partners and reproduction, and that their evolution might be explained by sexual selection.In the second half of the twentieth century, researchers realized that ornaments could be used in competition for nonsexual resources, such as access to food and territories outside reproduction (Tobias, Montgomerie, & Lyon, 2012; West-Eberhard, 1983)
Our results showed that some ornamental features were strongly affected by our treatments, while we found no evidence of treatment effects on other ornamental features
Body condition of birds at the beginning of the molt was positively linked to the YOchroma of their auricular patches in both experiments, suggesting that color production of that ornament is under an energetic trade-off
Summary
Understanding the evolution of conspicuous ornaments, often costly to produce and maintain, has been a long-standing focus of evolutionary biology (Andersson, 1994; Kuijper, Pen, & Weissing, 2012). Darwin (1871) laid the groundwork for this topic by observing that conspicuous ornaments could enhance access to sexual partners and reproduction, and that their evolution might be explained by sexual selection. Darwin (1871) laid the groundwork for this topic by observing that conspicuous ornaments could enhance access to sexual partners and reproduction, and that their evolution might be explained by sexual selection. In the second half of the twentieth century, researchers realized that ornaments could be used in competition for nonsexual resources, such as access to food and territories outside reproduction (Tobias, Montgomerie, & Lyon, 2012; West-Eberhard, 1983). West-Eberhard (1983) pointed out in her theory of social selection that ornaments can evolve whenever they enhance gene replication due “to differential success in social competition, whatever the resource at stake” (West- Eberhard, 1983). “subset of social selection in which the resource at stake is mates” (Lyon & Montgomerie, 2012; West-Eberhard, 1983).
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