title: Unexpectedly complex gradation of coral population structure in the Nansei Islands, Japan.
abstract: To establish effective locations and sizes of potential protected areas for reef ecosystems, detailed information about source and sink relationships between populations is critical, especially in archipelagic regions. Therefore, we assessed population structure and genetic diversity of Acropora tenuis, one of the dominant stony coral species in the Pacific, using 13 microsatellite markers to investigate 298 colonies from 15 locations across the Nansei Islands in southwestern Japan. Genetic diversity was not significant among sampling locations, even in possibly peripheral locations. In addition, our results showed that there are at least two populations of A. tenuis in the study area. The level of genetic differentiation between these populations was relatively low, but significant between many pairs of sampling locations. Directions of gene flow, which were estimated using a coalescence-based approach, suggest that gene flow not only occurs from south to north, but also from north to south in various locations. Consequently, the Yaeyama Islands and the Amami Islands are potential northern and southern sources of corals. On the other hand, the Miyako Islands and west central Okinawa Island are potential sink populations. The Kerama Islands and the vicinity of Taketomi Island are potential contact points of genetic subdivision of coral populations in the Nansei Islands. We found that genetic population structure of A. tenuis in the Nansei Islands is more complex than previously thought. These cryptic populations are very important for preserving genetic diversity and should be maintained.
authors.affiliation: Marine Genomics Unit Okinawa Institute of Science and Technology Graduate University 1919-1 Tancha Onna-son Okinawa 904-0405 Japan.
authors.forename: Yuna
authors.initials: Y
authors.lastname: Zayasu
authors.affiliation: Marine Biophysics Unit Okinawa Institute of Science and Technology Graduate University 1919-1 Tancha Onna-son Okinawa 904-0405 Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Nakajima
authors.affiliation: Sesoko Station University of the Ryukyus 3422 Sesoko Motobu Okinawa 905-0227 Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Sakai
authors.affiliation: Ishigaki Tropical Station Seikai National Fisheries Research Institute Fisheries Research Agency 148-446 Fukai-ota Ishigaki Okinawa 907-0451 Japan.
authors.forename: Go
authors.initials: G
authors.lastname: Suzuki
authors.affiliation: Marine Genomics Unit Okinawa Institute of Science and Technology Graduate University 1919-1 Tancha Onna-son Okinawa 904-0405 Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Satoh
authors.affiliation: Marine Genomics Unit Okinawa Institute of Science and Technology Graduate University 1919-1 Tancha Onna-son Okinawa 904-0405 Japan.
authors.forename: Chuya
authors.initials: C
authors.lastname: Shinzato
keywords: Acropora tenuis; gene flow; genetic diversity; microsatellite; population genetics