Genetic diversity in wild and reared populations of the Japanese bitterling Tanakia tanago (Cyprinidae)

Abstract

The Japanese bitterling Tanakia tanago is an endangered cyprinid species; thus, captive breeding programs are being conducted in various facilities as ex situ conservation. To examine the genetic diversity in one wild and three reared populations, and its changes during the process of captive breeding, sequences of the mitochondrial cytochrome b gene and control region were determined. The wild population, collected in 1993, was monomorphic. Although the reared population that originated from the wild population was almost monomorphic, a rare haplotype, distinct from all others by a relatively large sequence divergence, was also observed. In the other reared populations, some degree of genetic diversity had been maintained. A reared hybrid population, which originated from a mixture of three distinct populations, showed the greatest genetic diversity. These results suggest considerable genetic diversity within and among populations of T. tanago in the past. Although a loss of genetic diversity was observed in some year-classes of reared populations, there was no tendency for genetic diversity to decrease as a result of captive breeding, probably because offspring were obtained from multi-year-class parents in the captive breeding program. Accordingly, this breeding method should be appropriate for conserving the genetic diversity of T. tanago.