Meeting Abstract

P2.91  Monday, Jan. 5  Does a primary sex character vary with the degree of female-biased sexual size dimorphism: a test in the Poeciliidae. OUFIERO, Christopher E.*; POLLUX, Bart J.A.; BANET, Amanda I.; ARNOLD, Stephanie; GARLAND, JR, Theodore; Univ. of California, Riverside coufi001@student.ucr.edu

Sexual selection has been recognized as a factor that shapes the evolution of secondary sex characters, including aspects of morphology and behavior. However, can sexual selection operate on primary sex characters? We examined the relationship between female-biased sexual size dimorphism (SSD, measured as male/female standard length) and length of the gonopodium, a primary sexual character found in male poeciliid fish that is used to inseminate the females. The Poeciliidae includes over 200 species of freshwater, livebearing fish. Two main mating strategies occur in this family, gonopodial thrusting and courtship. Species that exhibit gonopodial thrusting exhibit few if any secondary sexual characters and a high degree of SSD; whereas species that exhibit courtship tend to have secondary sexual characters and a low degree of SSD. Therefore, it has been predicted that species with a high degree of female-biased SSD should exhibit larger gonopodia to aid in copulation. We tested this by examining SSD and proportional gonopodium length (gondopodium length/male standard length) in ~45 species of poeciliid fish in a phylogenetic context. We also examined other relationships with SSD and gonopodia, such as allometry of the traits. Preliminary non-phylogenetic results favor the prediction that species with a high degree of SSD have proportionally longer gonopodia than those with a low degree of SSD. Phylogenetically informed and additional results will also be discussed. Supported by NSF DDIG IOS-0709788 to T.G. and C.E.O, and NSF grant DEB-0416085.