Sperm-mediated gene flow and the genetic structure of a population of the colonial ascidian Botryllus schlosseri

Abstract

Concentrations of sibling sperm B. schlosseri decline rapidly within 50 cm of a source colony. In combination with spatially restricted dispersal of brooded larvae, limited dispersal of sperm should enhance the potential for genetic diversification and inbreeding, but analysis of allelic and genotypic frequencies at three independent, polmymorphic allozyme loci provides little evidence for microgeographic variation in gene frequencies. This lack of differentiation can be explained in terms of the absolute number (rather than concentration) of gametes and larvae dispersing from a point source, which may actually increase with distance. Levels of inbreeding are high. -from Author