TOTAL EVIDENCE REFUTES THE INCLUSION OF PERKINSUS SPECIES IN THE PHYLUM APICOMPLEXA

The phylogenetic affinities of the oyster pathogen Perkinsus marinus w ere investigated with morphology, 18S-like rDNA data and actin sequenc e data. Morphological investigations revealed that Perkinsus species d o not have a conoid and that other criteria which have been used to pl ace them in the Apicomplexa are general to alveolates. When considered separately, 18S-like rDNA and actin data sets each support a closer a ffinity for Perkinsus marinus with the dinoflagellates. However, each of these separate analyses possess their own biases and weaknesses. Us e of the phylogenetic principle of 'total evidence' in which data sets are combined in simultaneous analysis yielded a more robust hypothesi s that is stable both to character and taxonomic sampling. The resulti ng cladogram strongly corroborates the placement of Perkinsus species with the Dinoflagellida and not with the Apicomplexa.