DNA barcoding reveals that the common cupped oyster in Taiwan is the Portuguese oyster Crassostrea angulata (Ostreoida; Ostreidae), not C. gigas

Abstract

The Pacific cupped oyster, Crassostrea gigas, is one of the major aquacultural shellfish species that has been introduced to Europe and America from its native source in the West Pacific. In Taiwan, the cultivated cupped oysters along the west coast have been identified as C. gigas for over centuries; however, several molecular phylogenetic studies have cast doubt upon the existence of this species in Taiwan and adjacent waters. Indeed, our analyses of mitochondrial cytochrome oxidase I (COI) sequences from 313 Crassostrea collected from 12 locations along Taiwanese and southern Chinese coastlines confirm that all samples were the Portuguese oyster, C. angulata, rather than C. gigas. Multiple lines of evidence, including haplotypic and nucleotide diversity of the COI gene, demographic history, and population genetics, suggest that Taiwanese C. angulata is unique, probably experienced a sudden population expansion after the Last Glacial Maxima around 20,000 years ago, and has a significantly limited genetic connectivity across the Taiwan Strait. Our study applies an extended sampling and DNA barcoding to confirm the absence of C. gigas in natural and cultivated populations in Taiwan and southern China, where we only found C. angulata. We highlight the importance of conserving the gene pool of the C. angulata population in Taiwan, particularly considering the current threats by large-scale environmental disturbances such as marine pollution, habitat destruction, and climate change.

New insights about the introduction of the Portuguese oyster,Crassostrea angulata, into the North East Atlantic from Asia based on a highly polymorphic mitochondrial region

“…Thus, our results suggested that a demographic expansion event occurred recently in C. angulata. This is in agreement with the results of Hsiao et al (2016) who suggested that C. angulata in Asia experienced a sudden population expansion after the last glacial maxima. However, the results from Tajima's D, Fu's F and R 2 tests obtained in the present study and in other studies have to be considered cautiously since the coalescent model used may be inappropriate for highly fecund species such as C. angulata (Steinrucken et al 2013).…”

“…Moehler et al (2011) and Lallias et al (2015) reported nucleotide diversity values of 0.0044 and 0.0046 for C. gigas, respectively, with samples mainly collected in Europe but also in Canada and Japan. Hsiao et al (2016) found haplotype and nucleotide diversities (using mitochondrial cytochrome oxidase I sequences) in Asia being considerably higher in C. angulata than in C. gigas. This suggests that the number of C. angulata individuals introduced into the NE Atlantic must have been sufficiently high to reflect the genetic diversity of C. angulata in its native range.…”

Analysis of Genome-Wide Differentiation between Native and Introduced Populations of the Cupped Oysters Crassostrea gigas and Crassostrea angulata

“…Recent studies have shown that this species is widely distributed in Asian seas where it shows a high genetic diversity ( Wang et al. 2010 ; Sekino and Yamashita 2013 ; Zhong, Li, Yu, et al 2014 ; Hsiao et al. 2016 ), and also suggested a more complex history of transfers between Asia and Europe ( Grade et al.…”

Impacts of the combined exposure to seawater acidification and arsenic on the proteome of Crassostrea angulata and Crassostrea gigas

“…and C. angulata (Lam. ) are the most important cultured oyster species at a global level (Buestel et al, 2009;Hsiao et al, 2016), and hold major ecological (Grabowski et al, 2012) and socio-economic importance (FAO, 2015). However, these species present different ecophysiological traits (e.g.…”