Abstract
AimTo comprehend the phylogeographic patterns of genetic variation in anurans at Taiwan Island, this study attempted to examine (1) the existence of various geological barriers (Central Mountain Ranges, CMRs); and (2) the genetic variation of Bufo bankorensis using mtDNA sequences among populations located in different regions of Taiwan, characterized by different climates and existing under extreme conditions when compared available sequences of related species B. gargarizans of mainland China.Methodology/Principal FindingsPhylogenetic analyses of the dataset with mitochondrial DNA (mtDNA) D-loop gene (348 bp) recovered a close relationship between B. bankorensis and B. gargarizans, identified three distinct lineages. Furthermore, the network of mtDNA D-loop gene (564 bp) amplified (279 individuals, 27 localities) from Taiwan Island indicated three divergent clades within B. bankorensis (Clade W, E and S), corresponding to the geography, thereby verifying the importance of the CMRs and Kaoping River drainage as major biogeographic barriers. Mismatch distribution analysis, neutrality tests and Bayesian skyline plots revealed that a significant population expansion occurred for the total population and Clade W, with horizons dated to approximately 0.08 and 0.07 Mya, respectively. These results suggest that the population expansion of Taiwan Island species B. bankorensis might have resulted from the release of available habitat in post-glacial periods, the genetic variation on mtDNA showing habitat selection, subsequent population dispersal, and co-distribution among clades.ConclusionsThe multiple origins (different clades) of B. bankorensis mtDNA sequences were first evident in this study. The divergent genetic clades found within B. bankorensis could be independent colonization by previously diverged lineages; inferring B. bankorensis originated from B. gargarizans of mainland China, then dispersal followed by isolation within Taiwan Island. Highly divergent clades between W and E of B. bankorensis, implies that the CMRs serve as a genetic barrier and separated the whole island into the western and eastern phylogroups.
Highlights
Biogeography focuses on the study of the distribution of organisms and populations in distinct geographic space through geological time
The divergent genetic clades found within B. bankorensis could be independent colonization by previously diverged lineages; inferring B. bankorensis originated from B. gargarizans of mainland China, dispersal followed by isolation within Taiwan Island
Divergent clades between W and E of B. bankorensis, implies that the Central Mountain Ranges (CMRs) serve as a genetic barrier and separated the whole island into the western and eastern phylogroups
Summary
Biogeography focuses on the study of the distribution of organisms and populations in distinct geographic space through geological time. The CMRs, which include more than 260 peaks above 3,000 m, are a major biological barrier along the north-south axis and provide the niches leading to the genetic diversification of endemic organisms [16], such as freshwater fish [17,18,19], frogs [20], and squirrels [21]. The Miaoli Plateau and Formosa Bank, divided western Taiwan into three phylogeographical areas [18,20] This scenario is supported by the phylogenetic signatures obtained for a number of taxa, including frogs such as Buergeria robusta [20] and Sylvirana latouchii [22], and freshwater fishes such as Acrossocheilus paradoxus [23], Varicorhinus barbatulus [18], Hemimyzon formosanus [24], and Formosania lacustre [25]. Whether these patterns can be applied to other amphibians toad remains to be verified
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