Population genetics and demographic history of the ice goby (Leucopsarion petersii) in the Northwest Pacific

The Northwest Pacific, including Korea, is an interesting area for population genetic studies because of the dramatic Pleistocene sea-level change. The ice goby Leucopsarion petersii is endemic to Korea and Japan. We hypothesized that the ice goby has a population structure. To prove this, we analyzed the phenotypic and molecular characteristics of ice gobies collected from four localities in Korea and compared them with gobies from Japan. Meristic analysis revealed no significant differences, while the morphometric characters differed according to locality and sex. Haplotype networks based on mitochondrial DNA cytb and nuclear DNA myh6 sequences showed that the four localities share the same gene pool, suggesting that there was no or very weak population structure in the South Sea of Korea in the past or at present. All of the Korean ice gobies except the Wando ice goby were similar to ice gobies from the West Sea of Japan, but significantly different from ice gobies from the Pacific Ocean. At present, the Tsushima Warm Current may facilitate ice goby dispersal from the South Sea of Korea to the West Sea of Japan, which has resulted in the same gene pool in these two populations. Dispersal of the Wando ice goby might be difficult because of the complex oceanographic conditions near Wando. A Bayesian skyline plot analysis showed that ice gobies might have experienced two demographic expansions during the Pleistocene interglacial period. Further studies based on more sensitive microsatellite DNA markers are needed to clarify the recent differentiation history.