GENETIC STRUCTURE OF ENDANGERED BATA (LABEO BATA, HAMILTON) INFERRED FROM LANDMARK-BASED MORPHOMETRIC AND MERISTIC MEASUREMENTS AND ALLOZYME MARKERS

Abstract

Landmark-based morphometric and meristic counts were conducted to evaluate the population status of L. bata collected from three rivers namely the Tista, the Padma and the Brahmaputra and one hatchery sources. Seven of 13 morphometric characters, four of 8 meristic counts and eleven of 25 truss measurements revealed a significant inter-stock variation (P<0.01) among all samples. Plotting discriminant function DF1 and DF2 showed differentiation among stocks for both measurements. The first and second DF accounted 67.9% and 22.3% group variability respectively, explaining 90.2% of total group variability. A dendrogram based on morphometric and landmark distances placed the Tista and the Brahmaputra populations in one cluster with one sub-cluster with the Padma population while the hatchery population formed separate cluster. Allozyme electrophoresis was also carried out to assess the population genetic structure of L. bata with five enzymes (EST, GPI, LDH, MDH and PGM). The enzymes were controlled by eight presumptive loci (Est-1*, Gpi-1*, Gpi-2*, Ldh-1*, Ldh-2*, Mdh1*, Mdh-2* and Pgm*) where highest (six) polymorphic loci were found in Brahmaputra population. The mean proportion of polymorphic loci (%) observed as 62.50, 50, 75 and 62.50 in the Tista, the Padma, the Brahmaputra and the hatchery populations respectively. The highest (1.875) mean number of allele per locus was observed in the Brahmaputra river population. The mean proportion of heterozygous loci per individual was 19.48% and the average observed heterozygosity (Ho) and expected heterozygosity (He) were 0.195 and 0.176 respectively for all populations. The lowest (0.032) pair-wise population differentiation (FST) and highest (7.649) gene flow (Nm) were found in the Padma and the Brahmaputra river population indicating close relationship among them. In the Nei’s UPGMA dendrogram, the Tista population separated from other cluster by the highest genetic distance, D=0.171. The Padma and the Brahmaputra populations of L. bata made one cluster (D=0.009) and separated from the hatchery population by the genetic distance of 0.048. This study revealed considerable but inequitable variations among populations in wild and hatchery populations of L. bata using two methods at a time.