Mitochondrial DNA Diversity of Tor douronensis Valenciennes (Cyprinidae) in Malaysian Borneo

This study examines the population structure and taxonomy of Tar dour on ensis, an important indigenous freshwater fish species in Malaysian Borneo, by using sequence analysis of 466 base pairs of the mitochondrial cytochrome c oxidase I (COl) gene. A total of 62 fish samples were collected from five locations in Sarawak (N=54) and Sabah (N=8). The phylogenetic analysis using the Neighbour-joining (Nj) method supported the monophyletic status between T. douronensis and Tor tambroides, which further reinforced their taxonomic status as distinct species. The T. douronensis haplotypes were further divided into three major groups, with the Pelian fish from Sabah forming its own group (Cluster Ill) with strong bootstrap support. The large genetic differences separating the Sabah haplotypes from its Sarawak congener ssuggested that the Pelianfish might representa cryptic species. The current stud) showed high levels of intra and inter-popula tion variations in T. douronensis. With in all population variations, T. douronensis populations werefound, except in Bario. The presence of fixed haplotype differences along with high FST values among the populations of T. douronensis, support the conclusion that little or no migration occurred among the extantpopulations separated uy large geographic distances or river systems. However, the sharing of haplotypes between some such populations, f or example between Batang Ai and Bari o (H S6), and between Batang Ai and Ulu Limbang/Ba Kelalan (HS2) provided support that T. douronensis had a historically widesp read natural distribution in the region probably during the Quaternary period. Overall, the present study was able to shed light on the taxonomy and population structure of T. douronensis in Malaysian Borneo.