GENETIC-DIFFERENCES AMONG BLACK-LIPPED PEARL OYSTER (PINCTADA-MARGARITIFERA) POPULATIONS IN THE WESTERN PACIFIC

Seven populations of the black-lipped pearl oyster, Pinctada margariti fera, from the western Pacific were assayed for allozyme variation at 17 polymorphic loci from mantle biopsies. Levels of within population variation were high (mean number of alleles per locus averaged 6.8, me an direct-count heterozygosities averaged 0.575). Gene frequencies wit hin populations conformed to those expected under random mating. Signi ficant genetic differentiation between populations within reef groups and additionally between the Great Barrier Reef (GBR) and the Pacific islands (Kiribati and the Cook Islands) was revealed by hierarchical F -ST analysis. The average numbers of migrants per generation (N(e)m) a mong the Pacific islands and among the GBR populations was 6-8 and twi ce that between the Pacific islands and the GBR. This suggests a relat ively high gene flow among populations in Kiribati and the Cook Island s on an evolutionary time scale. However, the occurrence of significan t differences in gene frequencies among populations within reef groups suggests that genetic surveys of local populations should be undertak en prior to making any transfers of pearl oysters from other reefs in order to protect these genetic resources.