EAPSI: Investigating the Presence of a Female Bateman Gradient in the Japanese surfperch Ditrema Temminckii

Izumiyama Michael S, San Jose CA

Investigators

Abstract

Sexual selection is a major force driving evolution. This project will examine how sexual selection and reproduction vary in the Japanese surfperch, Ditrema temminckii, and compare the variation in number of mates and offspring to other surfperches endemic to the eastern Pacific coast. This project will utilize genetic information to understand the number of mates and fathers in a unique fish that exhibits internal fertilization and gestation to the sub-adult state. The research will be conducted at Osaka City University and Niigata University in collaboration with Dr. Satoshi Awata. This collaboration will provide unique data and new insights into how sexual selection varies between different species which diverged roughly 7 million years ago and have maintained a unique reproductive strategy. This project will measure sexual selection in female Ditrema temminckii by utilizing microsatellites to assign parentage to broods of pregnant female D. temminckii. The correlation between the number of sires and number of offspring (Bateman Gradient) will be determined and compared to other species of surfperch in the family Embiotocidae. In addition, sperm storage has been observed in D.temminckii, which uniquely positions this project to address a common criticism of female Bateman gradient studies: namely, that the number of sires is an underestimate of the actual number of mates. By tracking the number of mates progressively during the reproductive season and comparing to the number of sires detected, this study will be the first of its kind with the power to validate (or reject) the use of sires as an estimate of the number of overall mates. Therefore, this project aims to provide insight into the evolution of female sexual selection within a family of fishes that exhibit a derived reproductive strategy; by doing so, we may also resolve the controversy surrounding the use of sires as a proxy for the number of mates and clear the way for future female Bateman gradient studies in surfperch. This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by National Science Foundation and the Japan Society for the Promotion of Science.