Genetic population structure of the deep-sea whelk Buccinum tsubai in the Japan Sea

Abstract

The purpose of the present paper was to examine the genetic population structure of Buccinum tsubai in the Japan Sea. Mitochondrial 16SrRNA gene sequence analysis was performed with specimens from various stations in the Japan Sea. Mitochondrial lineages were clearly patterned geographically in four separate areas: the Hokkaido area, the Yamagata-Toyama area, the Yamato Bank area, and the San'in area. The main distribution depth range of B. tsubai is between 200 m and 1000 m isodepths, and the horizontal distance between the 200 m and 1000 m isodepth lines represents the specific spatial scale of the habitat (SSSH). These four areas were separated either by the complete discontinuity of the SSSH area or by its narrow spatial extension. Genetic distances between the main haplotypes of each area were calculated as Jukes-Cantor distances, the value of which ranged between 0.012 and 0.017. This value seemed to be unrelated to the geographic distance. There was no tendency for clustering according to depth. In future, the morphological characters of the four lineages of B. tsubai should be compared in detail in order to elucidate significant genetic differences among them.

A review of genetic intra- and interspecific relationships of deep-sea Buccinum and Neptunea species around Japan (with special reference to the Sea of Japan)

“…The monophyly of the San'in subpopulation and that of the other three subpopulations were supported by phylogenetic analysis (Iguchi et al 2004(Iguchi et al , 2007a contrary to our expectation that the monophyly of the San'in subpopulation and that of Yamato Bank one would be supported considering these geographic positions. This means that the San'in subpopulation was the first to be separated from the other three subpopulations in the past.…”

“…COI gene is known to be highly variable and more informative for population analysis than 16S rRNA gene (Hart and Podolsky 2005). In our results, B. tsubai included four genetically distinguishable subpopulations, which is consistent with the result using mitochondrial 16S rRNA sequences (Iguchi et al 2004(Iguchi et al , 2007a. The genetic structure of N. constricta was also clear and significant genetic differentiation was detected by analysis of molecular variance (AMOVA) among the four regions corresponding to the distribution of B. tsubai subpopulations, but the degree of the genetic differentiation was lower than that of B. tsubai (Fig.…”

“…The reduction of the habitat range of B. tsubai during the glacial periods in the Sea of Japan would also have facilitated the genetic differentiation among subpopulations of this species. This tendency is clear especially in the Yamato Bank population which is well recognized in the larger branch length of genotypes from the Yamato Bank subpopulation in the molecular phylogenetic trees (Iguchi et al 2004(Iguchi et al , 2007a.…”

“…In addition, this species has a eurybathic distribution pattern (208-1,355 m, Kato 1979). As a result of molecular phylogenetic analysis based on mitochondrial 16S rRNA gene, the haplotypes of B. tsubai were grouped into four major lineages (Iguchi et al 2004). These lineages were clearly patterned geographically in four separate areas characterized by the 1000-m isobath line: the Hokkaido area, the Yamagata-Toyama area, the Yamato Bank area, and the San'in area (Fig.…”

“…inclytum Pilsbry, 1904;B. isaotakii Kira, 1959;and B. tsubai Kuroda in Teramachi, 1933, which include four genetically different subpopulations (Iguchi et al 2004(Iguchi et al , 2007a as described above. In this analysis, we added the genetic data of four subpopulations of B. tsubai in order to compare the genetic distances between interspecies and intraspecies.…”