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We analyzed the ITS2 primary and secondary structure (including Compensatory Base Changes ( CBCs)) of 17 new Dunaliella strains (11 D. viridis, two D. tertiolecta, and four Dunaliella sp.), and compared these with other Dunaliella sequences available from the ITS2 database to circumscribe their taxonomic position. The ITS2 primary and secondary structure analysis positioned the majority of D. viridis strains in four main clades, showing that D. viridis is polyphyletic. The detection of at least one CBC among these clades strongly suggests that they could correspond to different biological species. Unexpectedly, while D. viridis var. euchlora ( CCAP19/21) was positioned within the subgenus Dunaliella, D. viridis var. palmelloides ( CCAP11/34) was positioned clearly outside this subgenus, suggesting that this taxon may not be properly placed in Dunaliella. Furthermore, the detection of at least three compensatory base changes ( CBCs) between D. viridis var. palmelloides ( CCAP11/34) and the other strains analyzed, confirm that this strain is a different species. For these reasons we propose re-naming D. viridis var. palmelloides ( CCAP11/34) to incertae sedis, and D. viridis var. euchlora ( CCAP19/21) to Dunaliella sp. Therefore, the ITS2 primary and secondary structure data suggest a taxonomic re-structuring of D. viridis. [ABSTRACT FROM AUTHOR]

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]

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]

Comparative ultrastructural data have shown that atleast two distinct groups exist within Carteria. Similarly, interpretations of variation in gross morphological features have led to the discovery of morphologically distinct groups within the genus. Partial sequences from the nuclear-encoded small and large subunit ribosomal RNA molecules of selected Carteria taxa were studied as a means of 1)testing hypotheses that distinct groups of species exist within the genus and 2)assessing monophyly of the genus. Parsimony analysis of the sequence data suggests that three Carteria species, C.lunzenis, C. crucifera, and C.oliveri, form a monophyletic group that is the basal sister group to all other ingroup flagellate taxa (including species of Chlamydomonas, Haematococcus, Stephanosphaera, Volvox and Eudorina). Two other Carteria taxa, C.radiosa and Carteria sp. (UTEX isolate LB 762), form a clade that is the sister group to a clade that includes Haematococcus spp., Chlamydomonas spp., and Stephanosphaera. Thus, the sequence data support the interpretation of ultrastructural evidence that described two distinct Carteria lineages. Moreover, the sequence data suggest that these two Carteria groups do not form a monophyletic assemblage. Parsimony analysis of a suite of organismal (morphologica, ultrastructural, life history and biochemical) character data also suggest two distinct lineages among the five Carteria taxa; however, the organismal data are ambiguous regarding monopophyly of these Carteria taxa. When the two independent data sets are pooled, monophyly of Carteria is not supported; therefore, the weight of available evidence, both molecular and organismal, fails to support the concept of Carteria as a natural genus. [ABSTRACT FROM AUTHOR]