Genetic differentiation among populations of the cave fish Schistura oedipus (Cypriniformes : Balitoridae)

DNA sequences were determined for portions of the mitochondrial control reg ion and 16S rRNA genes in five populations of Schistura oedipus, a troglobi tic fish from northwestern Thailand. Based on variation at seven sites out of 593 sequenced, the five populations fall into three groups, apparently i solated by altitude and distance. Nucleotide diversity within groups is on the order of 1.0 x 10(-3) while the extra increment of diversity among grou ps is on the order of 5.0 x 10(-3). While the groups are distinct, the leve l of differentiation among them is low enough to accept provisionally that the five populations represent a single species. On the basis of 16S sequen ce, Schistura oedipus appears to be more closely related to S. poculi than to S. reidi, a proposed sister taxon.