Phylogeny and taxonomy of Prasiolales (Trebouxiophyceae, Chlorophyta) from Tasmania, including Rosenvingiella tasmanica sp. nov.

The order Prasiolales includes trebouxiophycean green algae widely distributed in polar and cold temperate regions. Molecular data produced in recent years have shed considerable light on the phylogeny and genetic diversity of this group. Most of the information available for the order, however, has been obtained for the northern hemisphere; information for the southern hemisphere is comparatively scanty. Collections of Prasiolales were obtained from coastal sites in southern and eastern Tasmania and studied by microscopic examination, culture experiments and molecular analyses based on rbcL sequences. The results led to the discovery of a new species, Rosenvingiella tasmanica, which represents a previously unknown lineage within the genus Rosenvingiella. Culture observations and molecular data showed that collections from Tasmania previously identified as R. polyrhiza must be referred to R. constricta. This is the first record of this species for the southern hemisphere and outside of Eurasia and North America. In the same way, the molecular data revealed that the alga formerly known in Tasmania as Prasiola crispa is in fact referable to P. borealis. This organism was found both as a free-living alga and in a lichenized form similar to the original collections from North America. The rbcL gene sequence comparisons indicate a high genetic similarity between the Prasiolales of Tasmania and those of Pacific North America.