The role of ecological factors in determining phylogeographic and population genetic structure of two sympatric island skinks (Plestiodon kishinouyei and P. stimpsonii)
We conducted comparative phylogeographic and population genetic analyses of Plestiodon kishinouyei and P. stimpsonii, two sympatric skinks endemic to islands in the southern Ryukyus, to explore different factors that have influenced population structure. Previous phylogenetic studies using partial mitochondrial DNA indicate similar divergence times from their respective closest relatives, suggesting that differences in population structure are driven by intrinsic attributes of either species rather than the common set of extrinsic factors that both presumably have been exposed to throughout their history. In this study, analysis of mtDNA sequences and microsatellite polymorphism demonstrate contrasting patterns of phylogeography and population structure: P. kishinouyei exhibits a lower genetic variability and lower genetic differentiation among islands than P. stimpsonii, consistent with recent population expansion. However, historical demographic analyses indicate that the relatively high genetic uniformity in P. kishinouyei is not attributable to recent expansion. We detected significant isolation-by-distance patterns among P. kishinouyei populations on the land bridge islands, but not among P. stimpsonii populations occurring on those same islands. Our results suggest that P. kishinouyei populations have maintained gene flows across islands until recently, probably via ephemeral Quaternary land bridges. The lower genetic variability in P. kishinouyei may also indicate smaller effective population sizes on average than that of P. stimpsonii. We interpret these differences as a consequence of ecological divergence between the two species, primarily in trophic level and habitat preference.
KeywordsFilter bridge Phylogeography Population genetics Reptile Ryukyu Archipelago Scincidae
We are grateful to M. Tokuzato, T. Sasai, N. Kidera, T. Shiroma, T. Nakamura, Y. Yoshioka, Y. Koizumi, N. Sata and K. Mochida for their help in collecting specimens; T. Hikida for providing valuable comments throughout the study; two anonymous reviewers for many useful suggestions. A part of this study was conducted in a course of the conservation projects, “Current Status of the Kishinoue’s blue-tail skink”, which was organized by the Okinawa Prefectural Board of Education (OPBE), and was financially supported by OPBE and Japanese Agency for Cultural Affairs. We are also much indebted to M. Tokuzato for his help in obtaining the permission and management of the project.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted. This article does not contain any studies with human participants performed by any of the authors.
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