The phylogenetic position of enteromonads: a challenge for the present models of diplomonad evolution.
Unikaryotic enteromonads and diplokaryotic diplomonads have been regarded as closely related protozoan groups. It has been proposed that diplomonads originated within enteromonads in a single event of karyomastigont duplication. This paper presents the first study to address these questions using molecular phylogenetics. The sequences of the small-subunit rRNA genes for three isolates of enteromonads were determined and a tree constructed with available diplomonad, retortamonad and Carpediemonas sequences. The diplomonad sequences formed two main groups, with the genus Giardia on one side and the genera Spironucleus, Hexamita and Trepomonas on the other. The three enteromonad sequences formed a clade robustly situated within the diplomonads, a position inconsistent with the original evolutionary proposal. The topology of the tree indicates either that the diplokaryotic cell of diplomonads arose several times independently, or that the monokaryotic cell of enteromonads originated by secondary reduction from the diplokaryotic state.
Kolisko
Martin
M
Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic.
Cepicka
Ivan
I
Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic.
Hampl
Vladimír
V
Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic.
Kulda
Jaroslav
J
Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic.
Flegr
Jaroslav
J
Department of Parasitology, Faculty of Science, Charles University, Prague, Czech Republic.
D000818:Animals; D016054:DNA, Protozoan / Q000032:analysis; D004275:DNA, Ribosomal / Q000032:analysis; D016828:Diplomonadida / Q000145:classification* / Q000235:genetics*; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D012335:RNA, Ribosomal / Q000235:genetics; D014426:Turtles / Q000469:parasitology
D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D012335:RNA, Ribosomal