9416548 Yund PROJECT ABSTRACT This proposal will explore the impact of population density on the relationship between gamete production and reproductive success in a colonial ascidian. Previous research has found that variation in population density will affect the relationship between gamete production and reproductive success differently in male and female-phase colonies. The relationship between production and the number of fertilization obtained by a colony is expected to be linear in competitive situations (high population densities), but plateau in noncompetitive situations (low population densities) at the male gamete production level that allows a male to fertilize all of the eggs in his vicinity. In contrast, the relationship between egg production and the number of offspring produced by a colony is expected to be linear at low population densities (where male gamete limit the number of eggs fertilized), but plateau at high population densities due to constraints on the number of embryos that colonies can brood. These hypotheses will be tested in this research project by establishing experimental populations of ascidians that vary in gamete production under two density conditions and assaying male and female reproductive success. Male reproductive success will be assayed by using allozyme markers to assign paternity, while female reproductive success will be assayed by directly counting the proportion of eggs fertilized in each brood . This study will contribute to our knowledge of benthic marine organisms by examining the selective pressures that fertilization processes can exert on gamete allocation patterns.
