Phylogenetic relationship among various strains of Dunaliella (chlorophyceae) based on nuclear its rDNA sequences

Phylogenetic analyses of 15 strains representing 8 taxa of Dunaliella (D. salina, D. bardawil, D. pseudosalina, D. tertiolecta, D. parva, D. viridis, D. peircei and D. lateralis) belonging to both subgenera and all sections of the genus were carried out using the sequences of the nuclear rDNA spacers (internal transcribed spacer [ITS-1 + ITS-2]). The ITS data agreed with the traditional data in that D. lateralis (from subgenus Pascheria) is only distantly related to the seven taxa of the subgenus Dunaliella. The ITS data also supported the monophyly of the subgenus Dunaliella. Within the subgenus Dunaliella, sequence data resolved five phylogenetic groups; some isolates of A parva and D. salina separated into different clades containing other species. For example, D. parva UTEK 1983 (section Dunaliella) grouped with D. viridis CONC 002 (section Virides); the former has more nucleotides in common with D. viridis (93.2% similarity) than to its conspecifics (85.6% similarity). Likewise, the strains of D. parva CCMP 362 and CCAP 19/9 (section Dunaliella), the three strains of D. tertiolecta (section Tertiolectae), and the one strain of D. peircei (section Peirceinae) formed a strong phylogenetic clade (99%-100% support). Dunaliella salina UTEX 200 is more closely related to D. pseudosalina CONC 010 than to its conspecifics (95% similarity), even though the two taxa differ markedly physiologically. The results revealed that D. parva UTEX 1983 has been misidentified and should be renamed as D. viridis. Similarly, the strains of D. parva CCAP 19/9 and CCMP 362 and the strain UTEX 2192 of D. peircei should be renamed as D. tertiolecta. More physiological and molecular work needs to be done to elucidate the correct taxonomic position of D. salina UTEX 200 and D. pseudosalina CONC 010. Finally, the high ITS sequence variability found among the various strains of D. salina underlines the importance of further work to elucidate the species status in this complex taxon.