Abstract

The internal transcribed spacer 2 (ITS2) nuclear DNA was sequenced for six species of barbin fishes from Assam in the North Eastern region of India. The variations in the sequences were investigated to estimate nucleotide composition, nucleotide diversity, transition-transversion bias, genetic distance, and phylogenetic relationship. From the sequence analysis, it was found that the average G + C content (64.8%) was more than A + T content (35.2%). The nucleotide diversity (Pi) was found to be 0.04737. The number of transition substitutions was more than transversion substitutions and the transition–transversion bias was 1.16. Overall mean genetic distance was found to be 0.050 with a range from 0.005716 (between Puntius sophore and Puntius chola) to 0.084536 (between Pethia gelius and Systomus sarana). The phylograms constructed by neighbor-joining and maximum likelihood methods resulted in a similar topology where the monophyly of the Pethia group was recovered which consists of P. gelius, Pethia ticto, and Pethia conchonius. The two Puntius species (P. sophore and P. chola) were not clustered together and S. sarana remained a distinct taxon. The results of the present study partially validated the utility of the ITS2 DNA sequence in genetic diversity and phylogenetic studies in the barbin fishes.

Key words: ITS2, nuclear DNA, barbin fishes, genetic distance, phylogenetic relationship.