An international study led by Curtin University has put to bed a scientific debate dating back 176 years, confirming that two historically significant oyster species from Western Australia and Fiji are in fact distinct species.
By combining historic museum collections with modern DNA technology, the research provides new insights into marine biodiversity across the Indo-Pacific and helps strengthen the scientific foundation for future conservation efforts.
The research team revisited a long-standing question about the relationship between Saccostrea scyphophilla, first described in 1807 from Bernier Island in Shark Bay, Western Australia, and Saccostrea mordax, described from Fiji in 1850.
Since the naming of the oyster in Fiji, scientists have debated whether the two oysters represented separate species or whether they were simply different forms of the same oyster.
Saccostrea scyphophilla is found along WA's coast, across northern and eastern Australia, and the Indo-Pacific, while Saccostrea mordax occurs further north and east from Asia to Fiji.
Using modern DNA sequencing, the research has now confirmed the two oysters are genetically distinct species.
Lead author, Senior Research Officer Sherralee Lukehurst from Curtin's School of Molecular and Life Sciences said the findings demonstrate how modern genetic techniques can help answer questions that have challenged scientists for generations.
"Differences in the oysters' shells suggested there might be two species, but shell shape alone can be misleading because oysters change their shape depending on their environment and how closely they grow together," Ms Lukehurst said.
"DNA sequencing has given us the definitive answer, in what is an important breakthrough for understanding and managing marine ecosystems.
"Oysters are not just a food source - they are environmental engineers. They form reefs that provide habitat for many other species, help stabilise shorelines and improve water quality through filtration.
"Having a clear understanding of which species are present is an important foundation for conservation and management."
Research co-author Adjunct Professor Fred Wells, also from Curtin's School of Molecular and Life Sciences, said oysters are an important part of coastal ecosystems around the world.
"However, identifying oyster species can be challenging," Professor Wells said.
"This research provides new insights into oyster biodiversity across the Indo-Pacific, including Western Australia's diverse northern coastline, where many marine species remain poorly understood."
Part of the eDGES (eDNA for Global Environmental Studies) partnership between Curtin University and BHP, the research brought together scientists from Australia, Singapore, Fiji and the United States, combining DNA sequencing with historic museum collections to resolve the long-standing uncertainty.
The study involved analysis of historic specimens held in international collections, including material from the Smithsonian Institution and the Museum of Comparative Zoology at Harvard University, alongside newly collected samples from Bernier Island. A new reference specimen for Saccostrea scyphophilla was established and deposited at the Western Australian Museum.
The paper has been published in the international scientific journal Zootaxa.
