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Insights into the Evolution of Nuclear Dualism in the Ciliates Revealed by Phylogenetic Analysis of rRNA Sequences
Authors:BRIGITTE HAMMERSCHMIDT  MARTIN SCHLEGEL  DENIS H. LYNN    DETLEF D. LEIPE  MITCHELL L. SOGIN  IGOR B. RAIKOV
Affiliation:Zoologisches Institut, Universität, Tübingen, Auf der Morgenstelle 28, Tübingen, Deutschland;Universität Leipzig, Institut für Zoologie/Spezielle Zoologie, Talstrasse 33, 04103 Leipzig, Deutschland;Department of Zoology, University of Guelph, Guelph, Ontario, Canada NIG 2W1;Molecular Evolution, Marine Biological Laboratory, Woods Hole, MA 02543 USA;nstitute of Cytology, Academy of Sciences, St. Petersburg, Russia
Abstract:The small subunit rRNA gene sequences of the karyorelictean ciliates, Loxodes striatus and Protocruzia sp., and the heterotrichian ciliates, Climacostomum virens and Eufolliculina uhligi , were used to test the evolution of nuclear dualism in the Phylum Ciliophora. Phylogenies derived using a least squares distance method, neighbour joining, and maximum parsimony demonstrate that the karyorelictean ciliates sensu Small and Lynn, 1985 do not form a monophyletic group. However, Loxodes and the heterotrich ciliates form the first branch in the ciliate lineage, and Protocruzia branches, in distance methods, basal to the spirotrich lineage. It is proposed that Protocruzia be removed from the Class Karyorelictea, and placed in closer taxonomic association with the spirotrich lineage. The distribution of nuclear division types along the phylogenetic tree is consistent with the notion that macronuclei incapable of division represent a derived rather than a primitive or "karyorelictid" character trait.
Keywords:Loxodes    Protocruzia    Tracheloraphis    macronucleus    micronucleus    ciliate    division
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