Genetic differentiation among populations of the brooding soft coral Clavularia koellikeri on the Great Barrier Reef

The contribution of sexual and asexual reproduction, the spatial patterns of genetic structure, and the potential gene flow among populations were determined For the soft coral Clavularia koellikeri L (Octocorallia: Alcyonacea, Clavulariidae) at ten sites among six reefs from two well-separated regions of the Great Barrier Reef (GBR), Australia. Eight allozyme loci indicated that colonies of C. koellikeri separated greater than or equal to3 m were produced sexually. Genetic diversity was lower in the southern (18degreesS) compared with the northern (10degreesS) populations, suggesting that reefs closer to the southernmost limit of the distribution of C. koellikeri within the GBR (19degreesS) may represent a more marginal habitat for this species, High levels of genetic differentiation were significant at all spatial scales (sites within reefs, reefs, and regions) from <4 km up to 1,000 km, indicating that C. koellikeri has restricted dispersal, consistent with having brooded larvae.