Finding that these two genera do not have an immediate common ancestor, implies that this morphology and life-history must have been maintained unchanged from a more distant ancestry. Because of their respective placements as sister taxa to dinoflagellates and ciliates respectively, that organism with the same morphology ultimately must have been the ancestor of both of those groups and thus also of the Apicomplexa.
Mark E. Siddall
American Museum of Natural History,
New York, New York 10024, USA
Thomas A. Nerad
American Type Culture Collection,
Manassas, Virginia 20110, USA
Kimberly S. Reece
Eugene M. Burreson
Virginia Institute of Marine Science,
Gloucester Point, Virginia 23062, USA
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Phylogenetic analysis of Alveolata using stramenopiles and fungi to root the tree separates the morphologically indistinguishable species of Colpodella and Perkinsus . This suggests that their morphology is plesiomorphic (dashed line) and that it is representative of the ultimate ancestor of alveolates. Colpodella sp. [ATCC 50594] was isolated from brown woodland soil from Gambrill State Park, Maryland in 1993. The strain feeds on Bodo caudatus and was maintained in vitro at the American Type Culture Collection with its naturally ocurring bodonid prey. DNA isolation, amplification of SSU rDNA for Colpodella followed standard protocols. All other sequences were obtained from GenBank. Multiple alignment was effected with Clustal-W. The most parsimonious solution and branch support values (at nodes) were obtained with Nona11 using the ratchet.