Molecular phylogenetic analysis of class Colpodea (phylum Ciliophora) using broad taxon sampling

The ciliate class Colpodea provides a powerful case in which a molecular genealogy can be compared to a detailed morphological taxonomy of a microbial group. Previous analyses of the class using the small-subunit rDNA are based on sparse taxon sampling, and are therefore of limited use in comparisons with morphologically-based classifications. Taxon sampling is increased here to include all orders within the class, and more species within previously sampled orders and in the species rich genus Colpoda. Results indicate that the Colpodea may be paraphyletic, although there is no support for deep nodes. The orders Bursariomorphida, Grossglockneriida, and Sorogenida are monophyletic. The orders Bryometopida, Colpodida, and Cyrtolophosidida, and the genus Colpoda, are not monophyletic. Although congruent in many aspects, the conflict between some nodes on this single gene genealogy and morphology-based taxonomy suggests the need for additional markers as well as a reassessment of the Colpodea taxonomy.