Phylogeography and Identification of a 187-bp-Long Duplication within the Mitochondrial Control Region of Formosania lacustre (Teleostei: Balitoridae)

Abstract

An unusually long duplication was first discovered within the mitochondrial control region of the hillstream loach, Formosania lacustre. Over 68% of the 22 heteroplasmic individuals with the duplication were concentrated in the Tadu and Choshui Rivers of west-central Taiwan. This unusual duplication was located in the R1-repeated region of the mitochondrial genome, which includes a partial tRNA(superscript Pro) and the 5'-end control region. The duplication has a tendency to form secondary hairpin structures. For the phylogeographic analysis, the mitochondrial control region of 68 individual loaches from 11 different river systems (10 in Taiwan and 1 in mainland China) were amplified and sequenced. Nested clade analysis divided these loach populations into 2 distinct groups: northern and central groups. Higher and lower F(subscript ST) values were respectively revealed in the northern and central groups. Unexpectedly, a newly recorded population was established in this study. This population was previously classified as F. stigmata, but the mtDNA lineage analysis and morphological comparison indicated a strong similarity of this population with F. lacustre. Furthermore, the nested clade analysis indicated a long-distance dispersal route from central Taiwan to the mainland China; the mainland population later dispersed into northern Taiwan during recent ice ages. We concluded that colonization between the mainland China and central Taiwan was a major influence leading to the low genetic divergence and recent recolonization of F. lacustre.