Molecular Systematics of Freshwater Diaptomid Species of the Genus Neodiaptomus from Andaman Islands, India

Calanoid copepods belonging to the family Diaptomidae occur commonly and abundantly in different types of freshwater environment. Based on morphological taxonomic key characters 48 diaptomid species belonging to 13 genera were reported from India. Taxonomic discrimination of many species of these genera is difficult due to their high morphological similarities and minute differences in key characters. In the present study two species of the genus, Neodiaptomus, N. meggiti and N. schmackeri from Andaman Islands were examined based on morphological and molecular characters which showed low variation in morphology and differences in their distributions. The morphological taxonomy of Copepoda with genetic analysis has shown complementing values in understanding the genetic variation and phylogeny of the contemporary populations. In this study, a molecular phylogenetic analysis of N. meggiti and N. schmackeri is performed on the basis of mitochondrial Cytochrome c oxidase subunit I (COI) gene. The mtDNA COI sequence of N. meggiti and N. schmackeri is 650 bp long. The mtDNA COI 1 gene sequence data of N. meggiti exhibits a remarkable constancy throughout its distributional area ranging from North to south Andaman. Similarity of N. meggiti with other genera of the family varies from 67.6 to 75.5% while of N. schmackeri varies from 65.5 to 72.6% on the basis of COI gene sequences. While N. meggiti and N. schmackeri share a similarity of 92.3%, high COI gene sequence similarity among each other supports the morphological based data that they belong to the same genus. The phylogenetic relationship elucidated using three different tree-making algorithms, the neighbour joining, minimum evolution and maximum parsimony showed that five plankton specimens under study form two clusters and constituted a deeply rooted, evolutionarily distinct group, separated from the other related genera used in the analysis. The phylogenetic relationship of the two diaptomid copepod N. meggiti and N. schmackeri of Andaman is remarkably accurate when the Neighbor joining phylogenetic tree and as well as maximum parsimony phylogenetic tree are considered.