PHYLOGENY OF LOBOCHARACIUM (CHLOROPHYCEAE) AND ALLIES: A STUDY OF 18S AND 26S rDNA DATA1.

The phylogenetic affinities of Lobocharacium coloradoense were investigated by analysis of combined 18S and 26S rDNA data. Results from both parsimony and likelihood methods supported a close alliance among Lobocharacium , Characiosiphon , and Characiochloris. These three taxa formed a clade near the base of the “Dunaliella ” group within the chlamydomonad lineage. Protosiphon , which exhibits a siphonous habit similar to Characiosiphon and Lobocharacium , was not resolved as a close ally of the latter two taxa. The Lobocharacium alliance was characterized by the presence of an attachment pad associated with the nonmotile vegetative stage and pyrenoids that possess cytoplasmic invaginations. The pyrenoid feature is an ultrastructural trait that has now been observed in five different chlorophycean lineages. The Lobocharacium–Characiosiphon–Characiochloris clade is not predicted by any classifications of green algae. Additional taxon and data sampling need to be completed to resolve inconsistencies between the molecular phylogenetic evidence and at least some of the current family-level taxa. [ABSTRACT FROM AUTHOR]