Nucleotide diversity in populations of balitorid cave fishes from Thailand.

Genetic variabilities in four cave and eight surface species of balitorid freshwater fishes from Thailand were assessed using random amplified polymorphic DNA (RAPD). Cave species have consistently lower RAPD variation than surface species and it is hypothesized that this difference is a function of reduced population size in cave fishes. Indices of nucleotide diversity (pi) were calculated from the RAPD data and are four to five times higher for the surface species than the cave species: 6.4 x 10-3 vs. 1.4 x 10-3. The pi-values for cave fishes are significantly lower than those for surface balitorids and those measured in other species using RAPD/amplified fragment length polymorphism data.