Mitochondrial DNA analysis in ayu (Plecoglossus altivelis) raises an urgent conservation need for its southernmost population

Abstract

The central-marginal hypothesis predicts that genetic diversity decreases and genetic differentiation increases toward the species distribution margin. We analyzed the mitochondrial DNA control region of ayu (Plecoglossus altivelis) collected from different localities, including central and marginal populations, to test the hypothesis. The results show that the ayu populations at southern marginal habitats (Tien Yen River in Vietnam and Yakugachi River in Amami-oshima Island) displayed low genetic diversity (Haplotype diversity, H = 0.52 and 0.67; Nucleotide diversity, Pi = 0.01 and 0.006, respectively) and significantly differed from the central populations (p 0.05). This study showed that in ayu, the central-marginal hypothesis is valid in the southern direction but not in the northern direction. Urgent conservation is needed for the genetically distinct population in the degraded southern habitat with severely low genetic diversity.