What is the taxonomic status of East Asian otter species based on molecular evidence?: focus on the position of the Japanese otter holotype specimen from museum

<p>The Japanese otter (<i>Lutra nippon</i>), once inhabited in most islands of Japan, is now considered as an extinct species. Although the Japanese otter is regarded as a distinct species from the Eurasian otter (<i>L. lutra</i>), its phylogeny and taxonomic status are based on limited information on morphological and genetic data, and thus further clarification is required. Here, we assessed the phylogenetic relationship among the genus <i>Lutra</i> and taxonomic status of <i>L. nippon</i> by using the complete sequences of cytochrome <i>b</i> gene of its holotype. The present phylogenic trees supported that the genus <i>Lutra</i> specimens largely formed monophyletic group, with <i>L. sumatrana</i> as a basal to other <i>Lutra</i> species. Within <i>Lutra</i> species, <i>L. nippon</i> was distantly related with <i>L. lutra</i>. The European otter population of <i>L. l. lutra</i> were clustered together with its subspecies, <i>L. l. chinensis</i> rather than the same subspecies, Korean otter population. The discrepancy between the genetic data and traditional taxonomy justifies the necessity of reexamination of the current subspecific classification system of Eurasian otters. Level of genetic divergence between the holotype of <i>L. nippon</i> and <i>L. lutra</i> was two to three-fold lower than those among the other sister species of the Lutrinae. Based on the level of divergence between the <i>L. nippon</i> and <i>L. lutra</i>, and insufficient evidence of morphological difference between them, it is suggested that designation of Japanese otter as a separate species from L. <i>lutra</i> will be reconsidered.</p>