Zoological Studies

Phylogeography of the Taiwanese Endemic Hillstream Loaches, Hemimyzon formosanus and H. taitungensis (Cypriniformes: Balitoridae)

Tzi-Yuan Wang, Te-Yu Liao, and Chyng-Shyan Tzeng (2007) Variations in nucleotide sequences within the mitochondrial control region were used to determine the paleogeography of speciation and diversification of 2 balitorids endemic to Taiwan. Examination of 11 populations of Hemimyzon formosanus and 5 populations of H. taitungensis respectively revealed 23 and 11 haplotypes within the mitochondrial control regions. Utilizing the neighbor-joining method and maximum-parsimony trees, we showed the presence of 3 groups and 2 subgroups in H. formosanus, and 1 group in H. taitungensis. The nested clade analysis, a method with a higher resolution, revealed that the 1 group of H. taitungensis could be further divided into 2 subgroups on the minimum spanning network. The nested clade analysis predicted the evolutionary divergence of populations in H. formosanus due to past fragmentation; furthermore, dispersion among populations of H. taitungensis was caused by long-distance colonization. The moderate gene flow and low genetic divergence within the mitochondrial control region suggest that local range expansion and recent colonization occurred in H. formosanus in west-central Taiwan and in H. taitungensis in eastern Taiwan. Our study showed that one of the major influences on the speciation of both western H. formosanus and eastern H. taitungensis was the Central Mountain Range of Taiwan. Moreover, deep genetic divergence and morphological differences suggest new phylogenetic species exist within H. formosanus.