RIOS-CARDENAS, Oscar; Ohio University: Patterns of Parental Investment and Sexual Selection in Fishes: Do They Support Bateman�s Principle?

Bateman was the first to show a sex difference in variance in mating success. He proposed that this differential in mating success variance was caused by the differential investment in gamete production (males produce cheap sperm, while females produce expensive eggs). Since then, sex differences in variation in mating success have been used to explain sex differences in behavior (choosy females and promiscuous males) and morphology (sexual dimorphism). Later, Trivers pointed out that parental investment may include investments other than the production of gametes, and thus parental effort should also be considered in those species with parental care of the young. In general, the sex that contributes least will also be the sex with the highest variance in mating success and the one under strong sexual selection. Even though types of parental care in fishes are as diverse as the group, species with solitary male parental care are common. I explored the cost of paternal care in the pumpkinseed sunfish Lepomis gibbosus. Paternal care was energetically costly to the pumpkinseed sunfish as parental males significantly lost weight during the parental care period. Furthermore, the presence or size of the clutch did not improve the probabilities of obtaining more mates, thus the costs of care are not mitigated through increased mating success, as is the case in other substrate brooder fishes. However, parental males appeared to be under the influence of intersexual selection, which suggests that the costs of producing eggs by females might be higher than those incurred by parental males, or the operational sex ratio might be biased toward males. I explore the effects of this paternal investment in the Bateman gradient (or sexual selection gradient) for the pumpkinseed sunfish and other fishes with internal fertilization.