The Red Queen Visits Sage Grouse Leks

Coevolution between parasites and host is a sufficient although not necessary condition for the evolution of secondary sexual characteristics. I review evidence supporting the role of parasites in the maintenance of lek behavior in Sage Grouse (Centrocercus urophasianus). Males bearing avian malaria (Plasmodium pediocetii) or lice (Lagopoecus gibsoni or Goniodes centrocerci) have significantly lower reproductive success than noninfected males. Malaria-infected males attend leks significantly less frequently and lek attendance is highly correlated with male reproductive success. In addition, males with malaria secured copulations later in the breeding season with hens that were younger, in poorer condition and less successful than mates of malaria-free males. Lice create hematomas on the air sacs of males which females can detect to avoid lousy males. Results of our field studies are reinforced by experiments; captive males given antibiotics to reduce parasite loads are chosen more often by females in arena trials. Our results lend empirical support for Hamilton and Zuk's (1982) interpretation ofthe Red Queen's hypothesis, although many unknowns remain in our understanding of the interaction between parasite