Meeting Abstract
Carotenoid-based signaling is a classic example of honest signaling, in that acquiring or metabolizing carotenoids imposes costs such that those individuals expressing the most carotenoid rich signals are in the best condition. The red-backed fairywren (RBFW: Malarus melanocephalus) provides an interesting system in which to refine our understanding of the potential costs and mechanisms of the expression of carotenoid-based signals. In this species, males within a single population exhibit flexible reproductive phenotypes, where some males express red-black plumage that includes a sexually-selected vibrant red feather patch on their back, and other males exhibit a plumage identical to brown females, lacking the red patch. Previous work has shown that brown males are able to produce carotenoid based plumage within days of switching social status from subordinate helpers to dominant breeders. However, it remains unknown whether RBFW males maintain high levels of circulating carotenoids even when brown, or whether they only increase carotenoid levels when molting into red-black plumage. Established theory predicts that male carotenoid levels should be highest during molt, and low outside of the molt period because producing carotenoid coloration is costly. We tested this prediction by quantifying plasma carotenoid levels in brown males, red-black males and females. Preliminary evidence indicates that plasma hue of brown males more closely resembles that of red-black males, suggesting that there may be low costs of obtaining or metabolizing carotenoids in this system. Our findings highlight the complex ways in which carotenoids may be used to signal quality and set the stage for future research in this system.
