DNA entombed in archival seashells reveals low historical mitochondrial genetic diversity of endangered white abalone Haliotis sorenseni

Abstract

In this study we used decades-old shells of the endangered Northeast Pacific white abalone Haliotis sorenseni to produce high-quality DNA sequences for identification and historical diversity analysis. We obtained mitochondrial (mt) and nuclear DNA sequences (cytochrome c oxidase subunit I and histone H3 respectively) from shells with collection dates bracketing a period of population decline due to overexploitation, from throughout the species’ range. Illustrating the potential of shell DNA for forensic and conservation studies, we found two cases of misidentification among archival shell specimens. Diversity at the mitochondrial marker was lower in H. sorenseni throughout the 20th century than levels recently observed in two sympatric species that also suffered declines. The cause of comparatively low mtDNA diversity in white abalone is unclear; however, it cannot be exclusively linked to exploitation. DNA entombed in shells allowed us to directly establish historical genetic baselines for restoration of this endangered species. Vast repositories of shells exist in museum, aquaculture and private collections; the DNA contained within may be broadly investigated for studies of evolution, archaeology and conservation.