Molecular Divergence and Phylogenetic Positioning in Siluriformes Species Using mtDNA COI Gene

Abstract

Aim: Molecular divergence between species or a group of species is an efficient tool to trace the relation between them and assist in their better phylogenetic positioning with good bootstrap supports. The study has emphasized a chosen group of Siluriformes species available in the nearest water resource, which includes species from the families Clariidae, Heteropneustidae, Bagridae, and Siluridae.Materials and Methods: A standard barcoding protocol was followed, where the intraspecific and interspecific pairwise sequence divergences were calculated based on the Kimura 2-Parameter model, followed by phylogenetic tree clustering.Results: A considerable gap was found in the divergence values between species, which is sufficient to differentiate and delimit them. For intraspecific divergence, the average was found to be less than 1%, while the interspecific divergence varied from 16% to 24%. When the comparison was made on an average basis, the divergence between species (20.40%) was found to be approximately 25 times higher than intraspecific divergence (0.811%). When the divergence was calculated separately at each codon position, the maximum contribution was found from the 3rd codon position (78.4%) to the combined divergence, which was followed by the 1st codon position (6.87%) and the least contribution from the 2nd codon position (1.82%). The clustering analysis with Neighbor-Joining and Maximum Likelihood methods delimited the species with parallel phylogenetic clustering, supporting the divergence trends.Conclusion: The work provides a thorough picture of the relationship between divergence values and how this gap in divergence values plays a critical role in differentiating species while, at the same time, assisting in deciphering their taxonomic and phylogenetic positioning.

Keywords: Molecular divergence; Phylogenetic clustering; Siluriformes