Assessing the Speciation of a Cold Water Species, Japanese Sand Lance Ammodytes personatus, in the Northwestern Pacific by AFLP Markers

SIMPLE SUMMARY: Assessing the status of multiple highly divergent mitochondrial DNA (mtDNA) lineages and delimiting the evolutionarily significant units (ESUs) are the foundation of forecasting the influence of climate change on intraspecific genetic variation. In this study, we employed AFLP to investigate the genetic structure of Ammodytes personatus and compared the genetic variation of A. personatus in different ocean current systems. The incongruence between nuclear clades and previous mitochondrial lineages suggested that A. personatus is indeed composed of at least two genetically divergent cryptic species. Our results demonstrate that intra-species diversity should be taken into account to assess the influence of climate change on species. This study also highlights the value of the natural physical setting created by warm and cold ocean currents in eliciting a correlation between temperature and species distribution. In future studies, the exact range of temperature in both groups must be assessed with a sufficient number of samples to predict the influences of global climate change on both groups. ABSTRACT: The use of molecular techniques in biodiversity research increasingly results in the recognition of multiple divergent mitochondrial DNA (mtDNA) lineages below the morphospecies level. However, the overlapping distribution of multiple divergent lineages raises the question of whether some of these lineages are in fact cryptic species. Assessing the status of these divergent lineages, delimiting evolutionarily significant units (ESUs), and identifying the dominant evolutionary and ecological drivers are critical components of successful wildlife conservation and management strategies. Amplified fragment length polymorphism (AFLP) markers were applied to characterize the phylogeography pattern of a cold water species, the Japanese sand lance Ammodytes personatus, in warm and cold ocean currents. A total of 211 individuals sampled from 12 populations through the species’ range, including samples from Kuroshio Current, Oyashio Current, Tsushima Current, and Yellow Sea, were analyzed. The Bayesian assignment probability test and Neighbor joining (NJ) analysis divided these populations into two genetically and geographically distinct clades (northern and southern clades) characterized by different sea surface temperatures. The incongruence between nuclear clades and previous mitochondrial lineages suggested that A. personatus is indeed composed of at least two genetically divergent cryptic species. Pleistocene glaciation isolation after secondary contact, local thermal adaptation, and isolation by distance may explain the observed geographic pattern of two cryptic species and genetic structure within clades.