Morphological variation and preliminary survey of Isozyme / Allozyme markers in Rasbora daniconius of Sri Lanka

Abstract

Intra-specific morphological variation and differentiation among eight populations of the common freshwater fish Rasbora daniconius (Cyprinidae) were investigated. Significant heterogeneity and differentiation was found among some of the populations studied indicating limited geographic variation, as suggested by relatively large overlap in canonical scores among most of the samples. However, three populations could be separated convincingly from the rest; Pattiyapola, Dediyagala and Godapitiya. Cluster analysis based on the pair-wise inter-location morphological distinctiveness identified Dediyagala population as the most distinct one from all others. Mavil Aru population formed a distinct branch as well. The group of fish (P9) having close resemblance to R. daniconius but with a slightly different lateral stripe also separated. The preliminary genetic analysis was done to reveal existing genetic variation among three populations where eight enzymes were detected, but only three (LDH-I, PGM, ME-I) were clearly polymorphic. The present results show that R. daniconius in Sri Lanka is not phenotypically and genotypically homogenous. The absence of differences between population samples that experience highly limited present-day interchange may be partly explained by colonization history or environmentally controlled variability.