An experimental examination of dietary impacts on nuptial signal expression in threespine stickleback: does the nuptial signal indicate carotenoid and lipid stores?

Honest signalling systems associated with mate choice should evolve when female fitness is tightly tied to the quality of her mate. Females are entirely dependent upon the quality of their mate in threespine stickleback (Gasterosteus aculeatus, Linnaeus), since males undertake sole parental care of their offspring. Males of this species produce a bright red, carotenoid based nuptial signal. Here, we examine the honesty of the male signal as an indicator of male lipid reserves, an important component of male quality since the duration and intensity of male care is influenced by parental male lipid reserves. We manipulated dietary carotenoid and lipid composition to determine (i) if dietary lipid facilitated uptake of carotenoids and (ii) if the carotenoid based signal honestly signals male lipid stores. We found that dietary lipids did not influence the storage of carotenoids nor signal expression. We did not find support for the prediction that the red signal indicates lipid stores.