Unexpected population genetic structure in two closely related euphaeid damselflies from the Yaeyama and Taiwan Islands (Odonata: Euphaeidae)

Abstract

Abstract In general, population genetics theory predicts that a fragmented smaller population will contain relatively less genetic diversity than a larger population, and so will have a higher rate of genetic fixation due to random genetic drift or inbreeding. However, in this study, having analysed the genetic structure of the mitochondrial DNA COI region between two closely related euphaeid damselflies, we obtained unexpected results which contradict the theoretically expected patterns. Despite their geographical proximity, Euphaea yayeyamana was clearly genetically isolated on Ishigaki and Iriomote Islands, and no haplotype crossovers were observed. Even within each island, several diverse haplotypes were observed, indicating a significantly high haplotype intra-island diversity. However, the genetic diversity within Taiwan’s population of Euphaea formosa was significantly lower than that within either Ishigaki or Iriomote Island, even though Taiwan is significantly larger, with high mountain ranges that reach c. 4000 m a.s.l. and an abundance of habitats, all factors that should contribute to high genetic diversity. The current low diversity status for Taiwan’s population may be due to genetic bottleneck effects. In contrast, despite the very small population sizes of Ishigaki and Iriomote Islands coupled with the effects of glacial and interglacial geological events, they have maintained markedly high genetic diversity.