Phylogeny of Trichomonads Inferred from Small-Subunit rRNA Sequences |
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Authors: | JOHN GUNDERSON GREGORY HINKLE DETLEF LEIPE HILARY G MORRISON SHAWN K STICKEL DAVID A ODELSON JOHN A BREZNAK THOMAS A NERAD MIKLOS MÜLLER MITCHELL L SOGIN |
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Institution: | Center for Molecular Evolution, Marine Biological Laboratory, Woods Hole, Massachusetts 02543;Department of Biology, Central Michigan University, Mount Pleasant, Michigan 48859;Department of Microbiology, Michigan State University, East Lansing, Michigan 48824-1101;Protistology Department, American Type Culture Collection, Rockville, Maryland 20852-1776;The Rockefeller University, 1230 York Ave., New York, New York 10021 |
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Abstract: | ABSTRACT. Small subunit (16S-like) ribosomal RNA sequences were obtained from representatives of all four families constituting the order Trichomonadida. Comparative sequence analysis revealed that the Trichomonadida are a monophyletic lineage and a deep branch of the eukaryotic tree. Relative to other early divergent eukaryotic assemblages the branching pattern within the Trichomonadida is very shallow. This pattern suggests the Trichomonadida radiated recently, perhaps in conjunction with their animal hosts. From a morphological perspective the Devescovinidae and Calonymphidae are considered more derived than the Monocercomonadidae and Trichomonadidae. Molecular trees inferred by distance, parsimony and likelihood techniques consistently show the Devescovinidae and Calonymphidae are the earliest diverging lineages within the Trichomonadida, however bootstrap values do not strongly support a particular branching order. In an analysis of all known 16S-like ribosomal RNA sequences, the Trichomonadida share most recent common ancestry with unidentified protists from the hindgut of the termite Reticulitermes flavipes. The position of two putative free-living trichomonads in the tree is indicative of derivation from symbionts rather than direct descent from some free-living ancestral trichomonad. |
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Keywords: | Evolution rRNA 16S-like rRNA protist symbiosis |
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