Ancestral Haplotype Retention and Population Expansion Determine the Complicated Population Genetic Structure of the Hilly Lineage of Neolucanus swinhoei Complex (Coleoptera, Lucanidae) on the Subtropical Taiwan Island.

Abstract

Simple SummaryNeolucanus swinhoei is a widespread species of stag beetle distributed across the subtropical Taiwan Island. The biological features of weak flying capability, two-week adult lifespan, and strong dependence on forests are the key factors determining its genetic differentiation. We investigated the influence of historical climatic oscillations in Pleistocene on the distribution of N. swinhoei. The complex population genetic structure and dispersal routes of eastern populations are affected by the geographic isolation of the north/south-oriented Central Mountain Range (CMR) during periodical Pleistocene glaciations. Four possible shelters were inferred for the distribution of N. swinhoei in each geographic region during the periodical glaciations. The coexistence of widely distributed ancestral haplotypes and the locally derived ones are deduced to be the possible explanation of long-distance dispersal events for N. swinhoei. In the presence of the CMR, the northern and southern low mountains are proposed as alternative routes for N. swinhoei. The present study proposes dispersal routes from eastern to western Taiwan, in contrast to the more common scenarios of western-to-eastern dispersal found in other studies.The present study demonstrates that the complicated genetic structure of the hilly lineage of the Neolucanus swinhoei complex was driven by its biological features and habitat requirements as well as hindrance by the CMR during periodical Pleistocene glaciations. The results revealed a tendency of geographical differentiation and major and sub- lineage divergences before and after the Riss glaciation, followed by stable population growth during Würm glaciation. At least four refugia were inferred for N. swinhoei during the Riss–Würm glaciations. The ancestral haplotype retention in the cytochrome oxidase subunit I (COI) gene and compensated substitution in 16S rRNA gene is a possible evolutionary scenario resulting in the inconsistent evolution pattern between COI and 16S rRNA gene coupled with the long-distance dispersal of N. swinhoei. Although the CMR did hinder the dispersal of N. swinhoei, its ancestors may have dispersed to eastern Taiwan through the northern and southern low mountains of the CMR before the Riss glaciation. Our finding suggests that the population growth in the Würm glaciation led a dispersal back to western Taiwan, which is contrast to the more common dispersal scenario from western Taiwan to eastern populations proposed in other studies.