Genetic differentiation amongst populations of the coral Pocillopora damicornis off southwestern Australia

An electrophoretic study of genetic differentiation amongst local populations of the reef-coral Pocillopora damicornis was used to group coral heads into units defined as the area of effective dispersal of a clone, and termed “colonies”. For reefs off southwestern Australia, colonies were usually under a few hundred metres in extent. Although most new recruits within a colony were derived asexually, sexually produced propagules acted to connect populations outside the boundaries of a colony. Such connections were weak, and allelic frequencies varied considerably over a few kilometres. The primary agent of genetic differentiation was suggested to be the small effective population size resulting from the asexual proliferation of a few genotypes at any site. The effective number of genotypes per colony was approximately six. Asexual reproduction appears also to limit gene flow and accentuate selection in this species.