Phylogeography of Hemibarbus labeo (Cyprinidae): Secondary contact of ancient lineages of mtDNA

Nucleotide sequences of the D-loop control region of mtDNA were used to assess the genetic structure and phylogeography of Hemibarbus labeo in Mainland China and Taiwan. A hierarchical analysis of molecular variance of populations in 11 major streams from three geographical regions revealed significant structuring among populations and geographical regions. High levels of nucleotide diversity (p = 1.88%) and haplotype diversity (h = 96 ± 0.009%) suggest a large effective population size. A maximum likelihood tree based on mtDNA variation identified two ancient mtDNA lineages, which split approximately 3.39 million years ago. Overlapping distribution of the major lineages displayed low correspondence with geographical regions and reflects a scenario of secondary mergence after long isolation. Gene genealogy further revealed a unidirectional migration. Nevertheless, there existed a phylogeographical structure that mostly agreed with a biogeographical hypothesis. That is, within each lineage, a close phylogeny between populations of the River-Campagna and East-Pacific regions was supported by the mtDNA gene genealogy, although monophyly of each geographical region was not supported. The degree of genetic differentiation was correlated with geographical distances between populations, displaying a pattern of 'isolation by distance'. Gene genealogy of mtDNA revealed that Yangtzejiang population may act as a divergence centre of H. labeo. In addition, Taiwan population was colonized via a recent a founder event, likely from population Yangtzejiang River about 131 000 years before present. Low haplotype number and genetic variability also suggested possible bottleneck events in the Rongjiang and Dazhangjiang populations.