MOLECULAR EVOLUTIONARY ANALYSES OF NUCLEAR-ENCODED SMALL-SUBUNIT RIBOSOMAL-RNA IDENTIFY AN INDEPENDENT RHIZOPOD LINEAGE CONTAINING THE EUGLYPHINA AND THE CHLORARACHNIOPHYTA

The Rhizopoda comprise a diverse assemblage of protists which depend o n lobose or filose pseudopodia for locomotion. The biochemical and mor phological diversity of rhizopods has led to an uncertain taxonomy. Ri bosomal RNA sequence comparisons offer a measure of evolutionary relat edness that is independent of morphology and has been used to demonstr ate a polyphyletic origin of the Lobosea. We sequenced complete small subunit ribosomal RNA coding regions from the filose amoebae, Euglypha rotunda and Paulinella chromatophora (Euglyphina) to position these t axa in the eukaryote phylogeny. The neighbor-joining analyses show tha t E. rotunda and P. chromatophora share a monophyletic origin and are not closely related to any lobose amoebae in our analyses. Instead, th e Euglyphina form a robust sister group to the Chlorarachniophyta. The se results provide further evidence for the polyphyly of the Rhizopoda and support the creation of a new amoeboid lineage which includes the Euglyphina and the chlorarachniophyte algae; taxa with tubular mitoch ondrial cristae and filose or reticulate pseudopodia.