Population Structure ofAegialitesBeetles (Coleoptera, Salpingidae) on the Coasts of Hokkaido, Northern Japan

Abstract

We conducted a molecular phylogeographic analysis of Aegialites beetles sampled on the coasts of Hokkaido, northern Japan, using a partial sequence (553 bp) of the mitochondrial ND2 gene. The beetles are flightless and are adapted to the supralittoral zone of rocky shores. In all, 249 individuals from 17 populations were included in the molecular analysis. Haplotypes of the Aegialites beetles studied comprised two distinct lineages with different distributional ranges: one (lineage A) on the coasts of Hokkaido facing the Sea of Japan and the Sea of Okhotsk, and the other (lineage B) mostly on the Pacific coast and on the Shiretoko Peninsula in northeastern Hokkaido. These haplotype lineages clearly indicate two groups of populations, one comprising lineage A haplotypes (group A) and the other lineage B haplotypes (group B). Only one population, at Taisei facing the Sea of Japan on the Oshima Peninsula, contained a mixture of haplotypes from the two lineages. Genetic divergence among populations was larger in group B than in group A. Despite the unidimensional nature of the beetles' habitat, no correlation was found between the degree of genetic differentiation and geographic distance in either group of populations. Population genetic parameters suggested that the two lineages originated in the Pliocene, and that the populations in group A underwent a rapid increase in population size, whereas those in group B did not. We present a scenario for the allopatric divergence of the two lineages.