MALEMATING SUCCESS AND FEMALE PREFERENCE FOR MULTIPLE TRAITS IN THE TWOLINE PUPFISH (CYPRINODON BIFASCIATUS)

Using the twoline pup sh (Cyprinodon bifasciatus), a species with a resource-based polygy-nous breeding system, we examined male mating success in the wild, and we experimentally investigated effects of male body size and substrate type on female association patterns in the laboratory. Our purpose was to (a) identify the traits contributing to male reproductive suc-cess in the eld, (b) measure preferences for each trait independently in the laboratory, and (c) determine the relative importance of each trait. Field observations revealed that substrate type was the main determinant of male reproductive success: males defending territories on rocks mated signi cantly more often than males defending territories on silt or sand. Laboratory ex-periments supported the eld data, and revealed that the female preference for substrate type was independent of male body size effects. When given a choice between two males matched for size but differing in the type of substrates they were defending, females preferred the male on the rocky substrate over the male on the sandy substrate. Laboratory experiments also re-vealed a female preference for larger males when substrate type was held constant. Finally, when females were presented with a choice between a large male on a sandy substrate and