Molecular phylogeny of four ascidian species inferred from mitochondrial Cytochrome Oxidase subunit I (COI) sequence.

Ascidians is a crucial group for the studies of deuterostome evolution and the origin of chordates, yet little molecular work has been done to determine the evolutionary relationships and largely unexplored beyond a few species. The phylogenetic analysis are presented for four different species of solitary ascidians, Ascidia virginea, Ascidiella aspersa, Clavelina oblonga and Aplidium fuscum, obtained from Great Nicobar Biosphere reserve (GNBR). Mitochondrial Cytochrome Oxidase subunit 1(COI) gene was amplified and the genetic diversity at the phylogenic level was measured. Bar-coded sequences were extracted with BLAST format from NCBI and the genetic diversity of the submitted sequences were compared with the related ascidian species. Maximum divergences measured among the four species were as follows: Ascidia virginea (96%), Ascidiella aspersa (96%), Clavelina oblonga (94%) and Aplidium fuscum (97%). This is the first report of molecular phylogeny of ascidians from Great Nicobar Biosphere Reserve, Andaman and Nicobar Islands. From this study, we found some stable clades on the evolutionary relationships among these ascidian species that may prompt a reevaluation of some morphological characters.