Mitochondrial DNA sequence analysis from multiple gene fragments reveals genetic heterogeneity of Crassostrea ariakensis in East Asia

Abstract

The native Asian oyster, Crassostrea ariakensis is one of the most common and important Crassostrea species that occur naturally along the coast of East Asia. Molecular species diagnosis is a prerequisite for population genetic analysis of wild oyster populations because oyster species cannot be discriminated reliably using external morphological characters alone due to character ambiguity. To date there have been few phylogeographic studies of natural edible oyster populations in East Asia, in particular this is true of the common species in Korea C. ariakensis. We therefore assessed the levels and patterns of molecular genetic variation in East Asian wild populations of C. ariakensis from Korea, Japan, and China using DNA sequence analysis of five concatenated mtDNA regions namely; 16S rRNA, cytochrome oxidase I, cytochrome oxidase II, cytochrome oxidase III, and cytochrome b. Two divergent C. ariakensis clades were identified between southern China and remaining sites from the northern region. In addition, hierarchical AMOVA and pairwise U ST analyses showed that genetic diversity was discontinuous among wild populations of C. ariakensis in East Asia. Biogeographical and historical sea level changes are discussed as potential factors that may have influenced the genetic heterogeneity of wild C. ariakensis stocks across this region.

Molecular and Fitness Data Reveal Local Adaptation of Southern and Northern Estuarine Oysters (Crassostrea ariakensis)

“…This method is easy to visualize and can be extensively applied to studies of genetic diversity in C. ariakensis. Our findings were consistent with those of previous molecular taxonomic studies which found that C. ariakensis from northern China, Korea, and Japan were more closely related, but did not share a common haplotype with the southern populations using polymorphic microsatellite markers, mitochondrial COI and 16S rRNA sequence variation, and nuclear ITS-1 locus (Wang et al, 2004;Zhang et al, 2005;Xiao et al, 2010;Kim et al, 2014). The molecular data indicate that biogeographic barriers, such as the Yangtze River estuary, exist and isolate the northern and southern C. ariakensis populations.…”

“…Oysters from the northern estuaries cannot survive in southern environments, and the survival, metabolic rate, and growth for both populations showed greater performance in their native habitats than in their translocated non-native habitats. These findings provide critical evidence for adaptive divergence between the northern and southern C. ariakensis in China, which supports previous observations of their differentiation using limited neutral markers (Wang et al, 2004;Zhang et al, 2005;Xiao et al, 2010;Kim et al, 2014). Adaptive divergence in these fitness-related traits as well as in physiological and molecular parameters was also found in two congeneric oyster species, C. gigas and C. angulata, which are naturally distributed along the northern and southern coasts of the Yangtze River, respectively (Wang et al, 2010;Beck et al, 2011), using the same experimental approaches by combining common garden and reciprocal transplantation (Li et al, 2017.…”

“…Disconnected distribution and significant environmental gradients across inhabited estuaries imply differentiations in genomic components and plasticity among different populations, which requires investigations to assess their adaptive capacity in response to environmental challenges, particularly for elevated temperature and salinity. However, previous studies only revealed sequence variations between northern and southern populations of C. ariakensis separated by the Yangtze River estuary using neutral mitochondrial and nuclear gene markers, and speculated the occurrence of reproductive isolation between these two divergent populations (Wang et al, 2004;Zhang et al, 2005;Xiao et al, 2010;Kim et al, 2014). Hybridization experiments need to be carried out after knowing about genetic differentiation, which could provide the most informative findings to verify this hypothesis and further clarify their taxonomic status, e.g., whether they should be considered as two separate species or subspecies (Wang et al, 2004(Wang et al, , 2010.…”

Genetic variation and population structure of the Pacific oyster Crassostrea gigas in the northwestern Pacific inferred from mitochondrial COI sequences

“…The level of genetic diversity of C. gigas was characterized by moderate haplotype diversity (4 of 12 populations had low values, including LZ, PL, ZS and SU) and low nucleotide diversity, which was partly consistent with the previous conclusions reported by Sekino et al [52]. In addition, the level of genetic variation for C. gigas was relatively lower than that of some co-distributed bivalves (Table 5), such as C. sinensis [13], Tegillarca granosa [14], Crassostrea ariakensis [53] and Atrina pectinate [21]. A different population history of these species was assumed to be responsible for the differences in genetic variations.…”

Transferability of Cupped Oyster EST (Expressed Sequence Tag)-Derived SNP (Single Nucleotide Polymorphism) Markers to Related Crassostrea and Ostrea Species

“…For several decades, mitochondrial DNA (mtDNA) and microsatellite genetic markers have been the most common types used for molecular ecological studies (Beheregaray, 2008;Kim et al, 2014). In recent years, however, with the rapid increase in the availability of genomic information on oysters from expressed sequence tag (EST) collections, EST-derived simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs), a genomic approach to molecular marker development has become an attractive alternative to complement-existing markers because then can reduce time and cost compared with development of traditional genomic libraries.…”