Genetic characterisation of Emiliania huxleyi (Haptophyta)

Amongst the coccolithophorids, Emiliania huxleyi is the most successful and can form large scale blooms under a variety of environmental conditions. This implies extensive genetic variation within this taxon. Physiological, morphological and antigenic differences between clonal isolates support this suggestion. Our investigations into the level of genetic variation within the morphological species concept of E. huxleyi indicate that it is such a young taxon that sequence comparisons of both coding and non-coding regions cannot resolve the issue of how many separate taxonomic entities are involved. However, PCR-based genetic fingerprinting techniques do reveal extensive genetic diversity, both on a global scale and within major bloom populations in both space and time, Cell DNA content can also separate cells with morphotype A coccoliths from those with morphotype B coccoliths. Taken together with physiological and morphological evidence, these data suggest that the morphotypes of E. huxleyi should be separated at the variety level. We have used both nuclear and plastid rRNA sequence comparisons to confirm the place of E. huxleyi within the Haptophyta.