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Bayha, K.M., J.H. McDonald, and P.M. Gaffney, 2003. Molecular Systematics of the Invasive Ctenophore, Mnemiopsis sp., University of Delaware. Proceedings of the Third International Conference on Marine Bioinvasions, La Jolla, California, March 16-19, 2003, p. 11. Molecular Systematics of the Invasive Ctenophore, Mnemiopsis sp.The ctenophore genus Mnemiopsis currently contains two species (M. leidyi and M. mccradyi), with native ranges from Massachusetts to Southern Argentina. Over the past 20 years, these ctenophores have been introduced to the Black, Azov and Caspian Seas. In order to clarify the taxonomy and population genetics of Mnemiopsis, we have collected nuclear and mitochondrial sequence data from representatives of both putative species. The nuclear internal transcribed spacer regions (ITS) 1 and 2 were sequenced from 63 individuals collected from 22 different geographic regions spanning the ctenophores’ native and invaded ranges. We found no length variation in ITS-1 (233 bp) or ITS2 (228 bp). Furthermore, percent sequence divergence was low (0-0.9% for both ITS1 and ITS2) and within the range of intra-specific divergence found in other organisms, suggesting the presence of only one species of Mnemiopsis in all geographic ranges. Geographic analysis of ITS1/ITS2 composite genotypes indicates that South American Mnemiopsis (Argentina and Brazil) are isolated from North American populations (Atlantic/Gulf of Mexico coasts) and a weak population break exists around Cape Hatteras in North American waters. All invasive Mnemiopsis share genotypes with North American ctenophores, with the largest overlap occurring between invasive ctenophores and those south of Cape Hatteras into the Gulf of Mexico. Results from ongoing studies of additional nuclear and mitochondrial markers will also be presented. Contact: Keith Bayha, Smith Lab, University of Delaware, 700 Pilottown Rd.,
Lewes, DE 19958, USA |