Geographic variation of the Japanese spinous loach, Cobitis takatsuensis, inferred from allozyme analysis.

Genetic variation among river populations of the Japanese spinous loach, Cobitis takatsuensis, on Shikoku Island, was demonstrated by allozyme electrophoresis based on 40 presumed loci representing 20 enzymes and one non-enzymatic protein. Complete allelic replacement was not evident between populations in any one river system, but existed between populations in different river systems. The maximum genetic distance among populations reached 0.13 and the populations were divided genetically into four or five groups by river system on UPGMA and Neighbor-joining trees. In view of the genetic diversity of C. takatsuensis on Shikoku Island, the populations in three small river systems are thought to have originated from populations in one or the other of two large river systems with a bottle-neck effect. C. takatsuensis is currently designated as an endangered species in Japan. This study suggested that the populations of C. takatsuensis in each river system should be regarded as independent conservation units.