Meeting Abstract
Female preferences for male sexual traits are thought to be adaptive because they allow females to gain information about potential mates. The condition dependence of sexual traits is hypothesized to maintain the honesty of this information, where only healthy males who are well adapted to their environment can express the most elaborate traits. Melanin-based sexual traits, however, have long been thought of as strictly genetically controlled and there is often a lack of condition dependence with trait expression in adults. One explanation is that condition dependence for some melanin traits is limited to certain time periods, such as early development. In barn swallows Hirundo rustica erythrogaster, where melanin breast plumage is sexually selected, the majority of color variation can be attributed to variation in the developmental environment, yet color changes little within individuals as adults, despite annual molting of feathers. To understand the gene by environment interactions that generate this pattern, we cross-fostered eggs at the start of incubation and manipulated parasites in nests. We also collected data on maternal investment in egg composition and incubation, as well as nestling condition and physiology. Developing feather quills were collected from experimental nestlings for RNA analysis and compared with the color of emerged feathers when nestlings fledged. From these data, we identify how gene expression and environmental variation during development shape melanin color expression. This work provides new insight into the condition-dependence of melanin traits during development, and what females gain by using melanin-based signals during mate choice.
