First report of the European flat oyster Ostrea edulis, identified genetically, from Oyster Harbour, Albany, south-western Western Australia

Abstract

Ostrea angasi is the only large native ostreine species in southern Australian waters (i.e. New South Wales, Victoria, Tasmania, South Australia and Western Australia (WA)). It has also been recorded as a fossil from Late Pliocene calcarenites of the Roe Plain along the south-eastern coast of WA. Wild populations were harvested for food before and after European settlement. A sample of flat oysters from Oyster Harbour, Albany, WA, was typed for 16S and cytochrome oxidase 1 (CO1) mitochondrial (mt) DNA markers previously shown to be diagnostic for species of Ostreidae. Ostrea edulis was identified in the sample at an approximate 30% occurrence with O. angasi. Interspecific partial 16S and CO1 mtDNA sequence divergences, estimated using Kimura's two-parameter model, were 0.83% and 1.45%, respectively. The occurrence of O. edulis among native O. angasi populations has not hitherto been suspected and, thus, there has not been a legitimate morphological separation of the two. These results emphasise the value of molecular markers in: (1) discriminating morphologically plastic and closely related species; and, thus (2) the monitoring of species introduced into morphologically similar stocks. We caution against such introductions because of the possibility of the importation of oyster diseases (e.g. bonamiasis) and of this and other adverse impacts upon native species.