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Abstract

Tunas of genus Auxis are commercially and ecologically important fish of family Scombridae. There is currently no information concerning the genetic divergence between A. thazard and A. rochei. Therefore, a study was conducted to estimate the degree of genetic divergence between two species based on PCR-RFLP analysis of D-loop region (500 bp) of mitochondrial DNA in 100 individuals collected from Tuticorin (India). High level of genetic divergence (9.26%) was observed between A. thazard and A. rochei. Estimates of molecular diversity indices were higher in A. rochei (π = 3.8808; hd = 0.9641) compared to A. thazard (π = 2.2514; hd = 0.8441). Based on demographic parameters, population expansion of A. thazard estimated to begin about 67,167 years before present while of founding of A. rochei took place about 114,747 years before present in Indian Ocean. Thus, we conclude that A. rochei represents the ancestral species of genus Auxis.