YUND, P.O.*; JOHNSON, S.L.; CONNOLLY, L.E.; Univ. of New England; Univ. of Maine; Univ. of New England: Multiple paternity and subsequent fusion/rejection interactions in a colonial ascidian

The production of genetically variable offspring is a central function of sexual reproduction. The genetic composition of offspring subsequently affects many processes that operate on adults. Although much work has considered the costs and benefits of sexual vs. asexual reproduction, studies of the consequences of variation among sexually produced broods have been largely lacking. For free-spawning marine invertebrates, fertilization processes control the genetic diversity of offspring. Each egg can potentially be fertilized by a sperm from a different male, and hence levels of multiple paternity within a brood are an index of genetic diversity. Determinants of multiple paternity have not yet been explored, but variation is expected based on the interaction of mating systems with environmental conditions and population parameters. For sessile, colonial invertebrates, one important adult process that may be affected by the genetic composition of offspring is the fusion with or rejection of conspecific colonies. Colonies contact in the course of asexual growth, and are often related because of philopatric larval dispersal. Allorecognition systems that dictate fusion vs. rejection are under genetic control, so variation in multiple paternity within a brood should influence fusion rates. We have been exploring the possible relationship between multiple paternity and subsequent fusion/rejection interactions in a colonial ascidian (Botryllus schlosseri). Microsatellite assays of embryos brooded by colonies in natural populations indicate substantial variation in levels of multiple paternity. Fusion tests among recruits collected from settlement plates adjacent to maternal colonies were used to assay fusion frequency. Results may indicate the need to consider fertilization processes to fully understand adult fusion/rejection dynamics.