While the center of the world's marine biodiversity is undoubtedly the central West Pacific, the mechanisms by which such high biodiversity was generated and perpetuated are still under debate. In this study, we amplified both a mitochondrial DNA control region and 4 microsatellite loci to elucidate the historical phylogeography of the neon damselfish Pomacentrus coelestis in the West Pacific and used the distribution of alleles to test the 'Center of Origin' hypothesis. Two deeply divergent clades ('Pacific' and 'Micronesia') were identified, and the results of hierarchical analysis of molecular variance (proportion of variations among regions, Φ CT = 0.752, p < 0.01) and Bayesian assignments of genotypic data suggest a major genetic break between these clades. Demographic parameters, Tajima's D and Fu's Fs values, also indicate that these 2 lineages have different historical trajectories, indicative of the existence of more than 1 species within the complex currently assigned to P. coelestis. To avoid misinterpretation of past dispersal inferences, these 2 lineages were analyzed separately, and the Pacific clade was found to lack a distinct dispersal direction, probably due to rapid population expansion in the past. In contrast, the Micronesian clade showed a northeastwardly cladogenesis. Additionally, mixed lineages were found in the Raja Ampat Islands, suggesting that the Micronesian clade fits not only with the prediction of the Center of Origin hypothesis, but also the 'Center of Overlap' hypothesis. Our results suggest that multiple evolutionary processes may have acted on single species, either simultaneously or at different times, and have important implications for reef fish management in the West Pacific. KEY WORDS: Microsatellite · mtDNA · Management unit Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 458: [155][156][157][158][159][160][161][162][163][164][165][166][167] 2012 A number of hypotheses have been proposed to explain the biogeographic patterns found in the central West Pacific. The 'Center of Origin' hypothesis proposes that species evolved in the central West Pacific and then dispersed toward peripheral areas (Ekman 1953), and Pleistocene vicariance events might have played an important role in the speciation of marine taxa (Mora et al. 2003). The 'Center of Accumulation' hypothesis suggests that speciation occurs mainly in peripheral regions, with subsequent larval transport eventually resulting in the accumulation of species in the central West Pacific (Rosen 1988). The 'Center of Overlap' hypothesis suggests that the overlap of adjacent biogeographic regions or tectonic plates contributes to the high biodiversity of this region (Woodland 1983). These 3 hypotheses have been tested by the species distribution patterns of many marine taxa (Paulay 1996, Bellwood & Wainwright 2002, Paulay & Meyer 2002, Connolly et al. 2003, Allen 2008. However, using present species range data to test these hypotheses is potentially problematic b...

In this study, the partial mtDNA 16s rRNA gene and the S7 nuclear intron were used to resolve the phylogenetic relationship of four morphologically similar members of Ostorhinchus, including two colour morphs of Ostorhinchus properuptus (lined and dotted types), Ostorhinchus cyanosoma and Ostorhinchus holotaenia. Two different tree-building methods, maximum likelihood (ML) and a Bayesian-based method, yielded trees with highly similar topologies and high bootstrap values and posterior probabilities on the main nodes. Two main clades were recovered, suggesting that O. properuptus dotted type is closely related to O. holotaenia, and O. properuptus lined type members with O. cyanosoma. In addition, the genetic distance between the dotted and lined types of O. properuptus (0·299) was 23-fold higher than that between the dotted type and O. holotaenia (0·013). The dotted type can be identified by genetics as slightly differentiated in Japanese waters. It is treated as a population of the widespread species O. holotaenia.