Genetics of two species of soft coral, Sinularia flexibilis and Clavularia koellikeri, from the Great Barrier Reef

The genetic structure of 12 reef populations of the soft coral Sinularia flexibilis was studied along the Great Barrier Reef (maximum separation 1300 km). Up to 64 individuals per reef were collected at at 2 or 3 sites per reef, at a minimum of 5 m apart. Collection locations were: Dungeness, Cumberland, Pickersgill, Escape, Agincourt, Undine, Orpheus, Trunk, Rib, Cannon Bay, Deloraine, Hook Island. In two of these sectors, pairs of inshore and mid/offshore reefs were sampled.

Electrophoretic analysis of 9 polymorphic allozymes (GPI, HK, FBP, TPI, ME, MDH, VL, LGG, FLE) was made.

Departures of genotypic frequencies were evaluated for each locus using the Monte Carlo method using TFPGA software.

Genetic diversity and sexual versus asexual contributions to populations were further evaluated of multi-locus genotypes using: 1. Observed and expected genotype diversity ratios (Go:Ge). 2. Ratio of the [estimated] number of all individuals generated by sexual reproduction (N*) to the number of individuals (N). 3. Number of genotypes observed (Ngo) over N.

Spatial autocorrelation of genotypes within reefs was also investigated using Moran's I and Geary's c calculations.

To investigate the contribution of sexual and asexual reproduction in the soft coral Clavularia koellikeri (Octocorallia: Alcyonacea, Clavulariidae), populations were collected at ten sites among six reefs from two well-separated regions of the Torres Straits (Dungeness, Zuna, Wednesday Is), and the Great Barrier Reef (GBR; Pandora Reef, Orpheus Island, Britomart Reef), Australia. Eight allozyme loci were analysed. Genetic diversity was lower in the southern (18 degrees S) compared with the northern (10 degrees S) populations, suggesting that reefs closer to the southernmost limit of the distribution of C. koellikeri within the GBR (19 degrees S) 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 limited dispersal, consistent with having brooded larvae.