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An SSU rDNA barcoding approach to the diversity of marine interstitial Cercozoans, including descriptions of four novel genera and nine novel species

University of British Columbia

¹ E-mail: cchantan{at}interchange.ubc.ca

Environmental DNA surveys have shown a great deal of hidden diversity within the Cercozoa. Our investigation into the biodiversity of heterotrophic flagellates in marine benthic habitats in British Columbia, Canada have demonstrated several undescribed taxa with morphological features that resemble the cercozoan genera Cryothecomonas and Protaspis. We have described nine new species of marine interstitial cercozoans distributed into five genera, amongst which four are novel. Phylogenetic analyses of small subunit rDNA sequences derived from two uncultured isolates of Protaspis obliqua and nine novel cercozoan species (within four novel genera) provided organismal anchors that helped establish the cellular identities of several different environmental sequence clades. These data, however, also showed that the rarity of distinctive morphological features in cryomonads, and other groups of cercozoans, makes the identification and systematics of the group very difficult. Therefore, we applied a DNA barcoding approach as a diagnostic tool for species delimitation that used a 618-bp region at the 5' end of the SSU rDNA sequences. Nucleotide sequence analysis of this region showed high intergeneric sequence divergences of about 7% and very low intraspecific sequence divergences of 0-0.5%; phylogenetic analyses inferred from this barcoding region showed very similar tree topologies to those inferred from the full length of the gene. Overall, our study indicates that the 618-bp barcoding region of SSU rDNA sequences is a useful molecular signature for understanding the biodiversity and interrelationships of marine benthic cercozoans.