Microsatellite DNA analysis of southeast Australian Haliotis laevigata (Donovan) populations - implications for ranching in Port Phillip Bay

The genetic composition of greenlip abalone (Haliotis laevigata) from Point Cook in Port Phillip Bay was examined prior to the aggregation of individuals from this site for ranching. The very thinly distributed natural population at Point Cook was believed to be of low genetic diversity, because the animals all originated from a single spawning event 5 y previously. Animals from Point Cook were compared with other H. laevigata from two sampling sites within Port Phillip Bay, and two sites outside the Bay in Bass Strait, to examine their genetic diversity and origin. Variation was assessed at five microsatellite loci. Deviations from Hardy-Weinberg equilibrium (HWE) were observed at some loci in various populations, but the Point Cook population was in HWE at all five loci. Mean heterozygosity and number of alleles was similar in all populations. Hierarchical analysis of molecular variance indicated significant genetic variation among populations, but did not differentiate Port Phillip Bay from Bass Strait populations. Pairwise comparisons of multilocus F_STand R_ST indicated significant genetic differences between Point Cook and some populations, as well as between other populations, but no consistent spatial pattern of differentiation was observed. There was no significant correlation between genetic and geographic distance. The level of genetic variation observed in the Point Cook individuals was similar to that in individuals from the other four sites, and sufficient to support a ranching program. However, this variation should be monitored to maximize genetic potential, and avoid commercially undesirable effects of inbreeding. Implications of this study in relation to the management of a ranching population in Port Phillip Bay are discussed.