The phylogeny of the genus Nannochloropsis (Monodopsidaceae, Eustigmatophyceae), with descriptions of N. australis sp. nov. and Microchloropsis gen. nov.

Abstract:

Strains of the genus Nannochloropsis (Eustigmatophyceae) from the Australian National Algae Culture Collection were evaluated by DNA sequence analysis. Strains were first assessed by sequence analysis of a 900-base-pair region of the plastid rbcL gene (bar-code analysis). This analysis allowed us to identify most of the strains at specific rank. However, the strains CS-416 and CS-759 produced a unique rbcL DNA sequence and were sister to N. oceanica in the phylogenetic analysis. Complete rbcL sequences and nuclear 18S ribosomal (r)DNA sequences were produced for these two strains. The results of phylogenetic analyses of an alignment of the concatenated 18S rDNA and rbcL sequences for Nannochloropsis taxa revealed that strains CS-416 and CS-759 represent a new species, N. australis. In addition, the analysis provided strong support for erecting a new genus, Microchloropsis, comprising the species M. salina and M. gaditana.

Key Words::

• DNA bar code
• Eustigmatophyceae
• Microchloropsis
• Nannochloropsis
• rbcL
• rDNA

ACKNOWLEDGEMENTS

This research was supported by National Science Foundation grant DEB1248291 to K.P.F. and M.W.F. Additional equipment support was provided by grants from Arkansas INBRE (funded by the National Center for Research Resources (grant number 5P20RR016460-11) and the National Institute of General Medical Sciences (grant number 8P20GM103429-11) of the National Institutes of Health) to M.W.F. We thank Bobbie Okimoto at the University of Arkansas DNA Resource Center for sequencing and Marek Eliáš, University of Ostrava, for sharing the new rbcL primers Eu-rbcL-F1 and Eu-rbcL-R1. We thank Editor David Garbary, Associate Editor Antonio Jose Calado and two anonymous reviewers for helpful comments and careful editing.