Mitochondrial DNA phylogeography of Acrossocheilus paradoxus (Cyprinidae) in Taiwan

Nucleotide sequences of 3' end of the cytochrome b gene, tRNA genes, D-loop control region, and the 5' end of the 12S rRNA of mitochondrial DNA (mtDNA ) were used to assess the genetic and phylogeographic structure of Acrossoc heilus paradoxus populations, a Cyprinidae fish of Taiwan. A hierarchical e xamination of populations in 12 major streams from three geographical regio ns using an analysis of molecular variance (AMOVA) indicates high genetic d ifferentiation both among populations (Phi (ST) = 0.511, P < 0.001) and amo ng regions (<Phi>(CT) = 0.368, P < 0.001). Limited migration largely contri buted to the genetic differentiation. High nucleotide diversity (1.13%) and haplotype diversity (0.80%) were detected among populations. The degree of genetic differentiation was correlated with geographical distance between populations, a result consistent with the one-dimensional stepping stone mo dels. A neighbour-joining tree recovered by (DAMBE) supports the pattern of isolation by distance and reveals a closer relationship between population s of the central and southern regions. A minimum spanning network based on nucleotide substitutions reflected migration routes from populations of the central region to the northern and southern regions, respectively. Postgla cial colonization and expansion can explain the phylogeographical pattern. Single and ancient migration events may have allowed the northern region to attain the monophyly of mtDNA alleles. In contrast, most populations withi n geographical regions are either paraphyletic or polyphyletic due to the r elatively shorter time period for coalescence. Both low haplotype number an d genetic variability suggest a bottleneck event in the Chingmei population of northern Taiwan. Based on coalescence theory the monophyly of the Tungk ang population of the southern region may be associated with a founder even t.