Abstract
AbstratThe goldeye rockfish, Sebastes thompsoni, commercial rockfish catch in the Northwest Pacific Ocean, may influence its population structure. To clarify the population genetic structure of Korean S. thompsoni and its degree of hybridization with the most close species, Sebastes joyneri, we analyzed a mitochondrial (mt) DNA control region and eleven polymorphic microsatellite (ms) loci. S. joyneri individuals were clearly distinguished from S. thompsoni by the mtDNA control region and ms loci results, with single interspecific hybridization between two species suggesting no impact on genetic structure of S. thompsoni. Analysis of mtDNA revealed no population structure within S. thompsoni, suggesting the survival of a single population in southern refugia during the glacial period. The ms loci results, in contrast, showed two genetically distinct clusters within S. thompsoni: One was predominant throughout Korean coasts (from the Yellow Sea, via the Korea Strait to the East Sea); the other was predominant at Dokdo Island in the East Sea; and both occurred in similar ratios at Wangdolcho Reef in the East Sea. A possible factor that restricts gene flow between Korean coastal and offshore populations in the East Sea may be related to the complex oceanic current patterns such as eddies and upwelling, which represent impermeable barriers to population connectivity for this species. Our findings highlight that these two populations might be representative of two separate stock within Korean waters and maintain their geographically related genetic structure.
Highlights
In marine fishes, high dispersal capability and successful settlement during the early pelagic life stages provide opportunities for habitat expansion, maintenance of sustainable population sizes, and the exchange of genetic material between geographically distant populations (Jones et al, 2009; Kritzer & Sale, 2010; Strathmann et al, 2002)
The present study found discordance between the mtDNA and msDNA loci results; the former suggested that Korean S. thompsoni comprised a single panmictic group, but the latter suggested that it comprised two genetically distinct clusters: Cluster 2 was predominant in Korean coastal locations; Cluster 3 was predominant at Dokdo Island; and both clusters occurred in similar ratios at Wangdolcho Reef
A relatively high admixture proportion between the two clusters in most sampling locations, in particular Chujado and Yokjido Island, has been identified, possibly due to disassortative mating associated with bias in occurrence ratios in each cluster
Summary
High dispersal capability and successful settlement during the early pelagic life stages provide opportunities for habitat expansion, maintenance of sustainable population sizes, and the exchange of genetic material between geographically distant populations (Jones et al, 2009; Kritzer & Sale, 2010; Strathmann et al, 2002). As Sebastes species are ovoviviparous (i.e., the female releases free-swimming larvae), the range and direction of transport during dispersive phases of the early life cycle are potentially important influences on population structure (Love et al, 2002). Japanese halfbeak (Hyporhamphus sajori) and Korean rockfish (Sebastes schlegelii) are good examples to demonstrate this; both species spend their early life stages in drifting seaweed, showing very high genetic homogeneity despite the geographic distance between populations (Gao et al, 2016; Uchida & Shojima, 1958; Yu, Kai, & Kim, 2016). The objective of this study was to clarify the connectivity among local populations of Korean S. thompsoni and its degree of hybridization with S. joyneri using the mitochondrial (mt) DNA control region and 11 polymorphic microsatellite loci
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