Inter and intra-specific relationship between goat fishes Upeneus vittatus (Forsskal, 1775) and Upeneus tragula based on their mtCOI gene from Palk Bay and Gulf of Mannar Coast (Mandapam, Tamil Nadu) of India

The identification of goatfish has been commonly performed morphologically. Although traditional patterns of identification are available, there are still difficulties in differentiating species because of their similar appearances. The present study attempted to differentiate the two species Upeneus vittatus and U. tragula based on their mtCOI gene and to study their phylogenetic relationships. Six specimens of U. tragula were collected from the Gulf of Mannar and Palk Bay, and their mtCOI gene was sequenced and grouped with the mtCOI of three U. tragula (KU499646, KX887495, and KC147800), and mtCOI of three U. vittatus (KX024776, KT823808, and KU944141) from the NCBI portal. The neighbor-joining tree revealed that the U. vittatus and U. tragula had a common ancestor. Two specimens of U. tragula, one from the Gulf of Mannar and one from Palk Bay (MN319645 and MN319650) were very closely related to the U. vittatus of Gulf of Mannar (KX024776) with a similarity of 86.34 % and 86.99 % respectively which denotes they might have evolved from the U. vittatus due to allopatric speciation. U. tragula (MN319645 and MN319650) are closely related to each other. The overall mean genetic distance, d = 0.2, indicated that the 12 specimens had conserved regions. The study also revealed that speciation occurs among U. tragula populations in both the Gulf of Mannar and Palk Bay, which might be due to migratory populations or allopatry within a cryptic species.