Molecular evidence for recolonization of Ceramium japonicum (Ceramiaceae, Rhodophyta) on the west coast of Korea after the last glacial maximum

Abstract

Abstract The Yellow Sea, located between the Korean Peninsula and mainland China, was completely exposed during the last glacial maximum of the Pleistocene when the sea level was 120–130 m below the present level. We studied patterns of genetic variation in a marine red alga to examine whether the recent recolonization of algal populations occurred on the west coast of Korea after the end of the last glacial maximum. In total, 53 specimens of the red alga Ceramium japonicum were collected in Korea and Japan. We examined the geographic distribution of haplotypes and patterns of migration using mitochondrial cox1 and plastid rbcL. From the specimens collected, 22 cox1 haplotypes and eight rbcL haplotypes were identified. The network and neutrality tests for cox1 support three clusters (which are geographically grouped into east, south, and west coast populations) and provide evidence for population expansion on the west coast. The levels of gene flow were high in the south coast→west coast direction. Analysis of molecular variation in two protein-coding genes revealed significant genetic structure among the three coasts. The results support the concept that C. japonicum populations recolonized the west coast from the south coast following sea level rise in the northern hemisphere after the last glacial maximum during the late Pleistocene.