Phylogenetic positions and taxonomic assignments of the systematically controversial genera, Spirotrachelostyla, Uroleptopsis and Tunicothrix (Protozoa, Ciliophora, Stichotrichia) based on small subunit rRNA gene sequences

摘要

The phylogenetic positions of three systematically controversial genera of ciliates, Spirotrachelostyla, Uroleptopsis and Tunicothrix, have never been established by molecular data. The small subunit rRNA genes of three species, S. tani, U. citrina and T. wilberti, were sequenced and added to existing sequences of stichotrichs and other ciliates to construct phylogenetic trees. Results indicate the following: (1) Uroleptopsis is most closely related to species of Pseudokeronopsis, supporting its assignment to the family Pseudokeronopsidae; (2) one sampled Tunicothrix branches sister to the two sampled Parabirojimia, and this supports the placement of Tunicothrix in the Parabirojimidae; (3) Spirotrachelostyla clusters consistently with Trachelostyla to form a distinct, divergent clade that associates with Amphisiella at the base of the entire sporadotrich-urostylid clade, confirming the hypothesis that Spirotrachelostyla should be placed in the family Trachelostylidae.