Cladistic phylogeny of Calanoid copepods (Crustacea: Arthropoda) using 18S rRNA gene

This study establishes a molecular phylogeny for calanoid copepods based upon 18S rRNA gene including 4 families from 2 super families. For this investigation, copepods were collected from different habitats of the Tamil Nadu Coast (Southeast India). The tree topology confirmed the monophyletic state of the families Pontellidae and Pseudodiaptomidae with high bootstrap values of 82 and 98% respectively. The family Acartiidae derived from the Glade Pontellidae with a genetic distance ranged from 11.2 to 14.5%. However, the Paracalanidae family showed the highest genetic distance of 17.5% to the superfamily Centropagoidea and formed a seperate Glade. We have also reconstructed phylogenetic trees using neighbor-joining (NJ)), maximum-likelihood (ML) and minimum evolution (ME) methods by retrieving 10 reference sequences from the NCBI that were compared with our own 15 calanoid copepod sequences. All these trees resolved clear separation of calanoid copepods based on family and superfamily level and hence 18S rRNA gene is a suitable molecular marker to study the relatively recent cladogenetic events among calanoid copepods.