Population genetic structure and distribution patterns of sexual and asexual gecko species in the Ogasawara Islands

Abstract

Asexual reproduction lacks genetic diversity but is predicted to be advantageous for dispersal and for increasing abundance relative to sexual reproduction. The oceanic Ogasawara Islands are inhabited by two gecko species, the asexual (parthenogenetic) all-female Lepidodactylus lugubris and the sexually reproductive Hemidactylus frenatus. This situation offers a unique opportunity to examine the relationships among sexuality and the abundance, distribution, and genetic diversity of the two species. A total of 445 geckos were collected across nine islands, and the population genetic structure of both species was estimated using microsatellite markers. Lepidodactylus lugubris was collected on all nine islands and consisted of two widely distributed clones: one diploid and the other triploid. In contrast, H. frenatus was limited to four islands and exhibited variation in population genetic structure among islands, with some bottleneck effects. Successful dispersal may be more frequent in L. lugubris than in H. frenatus; therefore, the asexual reproductive strategy of L. lugubris appears to have contributed to its dispersal success and increased abundance among the small oceanic islands. However, the absence of H. frenatus on islands not inhabited by humans may be partially explained by their different microhabitat preferences, as H. frenatus collection sites were relatively more confined to artificial substrates in towns and along roadways compared to L. lugubris. Moreover, the colonization histories of these two geckos have not yet been assessed; therefore, further study is needed to confirm the effects of sexuality on the population dynamics of these species.