Protistology 5 (4) 281-302 (2008)
The twilight of Sarcodina: a molecular perspective on the polyphyletic origin of amoeboid protists*
Jan Pawlowski
Department of Zoology and Animal Biology, University of Geneva
Summary
For convenience, the traditional classifications placed all amoeboid protists in the group Sarcodina, subdivided based on the type of pseudopodia into
Rhizopoda and Actinopoda. Early molecular phylogenies provided evidence for the polyphyly of Sarcodina, but the relationships between different amoeboid taxa
remained largely unresolved. It was only recently that a more congruent view of the phylogeny of amoeboid protists emerged from multigene analyses. According
to this view, the majority of amoeboid protists are placed in the supergroups Amoebozoa and Rhizaria. Amoebozoa include almost all lobose amoebae and
mycetozoans, while Rhizaria comprise the majority of protists bearing filopodia, reticulopodia and axopodia. Both supergroups also contain a variety of free-living
flagellates and some parasitic lineages. Te few amoeboid protists that did not find their place within these two supergroups have been placed by molecular
phylogenies either among excavates (Heterolobosea), opisthokonts (Nuclearia), and stramenopiles (Actinophryida, some Filosea), or as independent lineages
(Centrohelida, Breviata). Although the molecular data clearly indicate that the pseudopodial structures have been developed several times in the history of eukaryotes,
they also show that a large diversification of amoeboid protists occurred only twice, in lineages leading to Amoebozoa and Rhizaria. Te evolution of different types
of pseudopodia within these supergroups constitutes a new challenge for future phylogenomic studies of amoeboid protists.
| Load PDF |
Back to Contents |
|