SEXUALLY SELECTED COLOR IN MALE STICKLEBACKS - A SIGNAL OF BOTH PARASITE EXPOSURE AND PARASITE RESISTANCE

Individual variation in parasite exposure is often overlooked in studies of the role of parasites in the evolution of mate choice. Here we outline how androgen and carotenoid dependent red breeding coloration might broadcast reliable information about parasite exposure and genetic resistance to common parasites in a population of male three-spined sticklebacks (Gasterosteus aculeatus). Copepods, which are important prey for sticklebacks contain carotenoids essential for development of breeding coloration, but are also intermediate hosts for common parasites of sticklebacks. Of the five parasite species found in 46 males, only those three transmitted through copepods show associations with intensity of red breeding coloration. Two of these (Diphyllobothrium spp.) show a positive relationship with intensity of red coloration, whereas the apparently more pathogenic Schistocephalus solidus is negatively associated with intensity of red breeding coloration. The signal broadcasted by bright red males may thus be operating both as a sexually selected handicap, and as a reliable signal about degree of parasite exposure.