Phylogeny and taxonomy of Prasiolales (Trebouxiophyceae, Chlorophyta) from Tasmania, including Rosenvingiella tasmanica sp. nov. MO ´ NICA B.J. MONIZ 1 ,FABIO RINDI 1,2 * AND MICHAEL D. GUIRY 1 1 Ryan Institute for Environmental, Marine and Energy Research, National University of Ireland, Galway, Ireland 2 Dipartimento di Scienze del Mare, Universita ´ Politecnica delle Marche, Via Brecce Bianche, I-60131 Ancona, Italy MONIZ M.B.J., RINDI F. AND GUIRY M.D. 2012. Phylogeny and taxonomy of Prasiolales (Trebouxiophyceae, Chlorophyta) from Tasmania, including Rosenvingiella tasmanica sp. nov. Phycologia 51: 86–97. DOI: 10.2216/10-103.1 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. KEY WORDS: Australia, Biogeography, Phylogeny, Prasiola, Prasiolales, rbcL, Rosenvingiella, Tasmania, Taxonomy, Trebouxiophyceae INTRODUCTION The green algal class Trebouxiophyceae includes a large assemblage of unicellular and multicellular microchloro- phytes distributed in virtually every type of terrestrial and aquatic habitat and often involved in lichen symbioses (Lewis & McCourt 2004). The order Prasiolales represents one of the most ecologically differentiated lineages among the Trebouxiophyceae because it includes taxa distributed in marine, freshwater and terrestrial habitats in polar and cold-temperate regions (Ettl & Ga ¨rtner 1995; John 2002; Rindi 2007). This order includes algae consisting of uniseriate filaments, ribbon-like thalli, expanded monostro- matic blades, packet-like colonies and pseudoparenchyma- tous axes (Knebel 1935; Ettl & Ga ¨rtner 1995), characterized by an unusal combination of morphological and ultrastruc- tural characters that made their phylogenetic position uncertain for a long time (O’Kelly et al. 1989; Hoek et al. 1995; Sherwood et al. 2000). As currently circumscribed, the Prasiolales includes one family (the Prasiolaceae) and about 35 species belonging to the genera Prasiococcus Vischer, Prasiola Meneghini, Prasiolopsis Vischer and Rosenvingiella P.C. Silva (Guiry & Guiry 2010). The genus Trichophilus Weber-van Bosse, which was formerly believed to belong to this group, was recently shown to represent a sepa- rate lineage in the class Ulvophyceae. Suutari et al. (2010) showed that the culture SAG84.81, from which the sequences EF203012 and AY762601 were obtained, does not represent the genuine T. welckeri and is a prasiolalean alga probably referable to Prasiolopsis. Molecular studies published in the last 10 years have robustly established the placement of the Prasiolales within the Trebouxiophyceae (Karsten et al. 2005; Darienko et al. 2010) and have greatly advanced our understanding of the phylogeny and diversity of this group (Sherwood et al. 2000; Rindi et al. 2004, 2007; Perez-Ortega et al. 2010). Molecular data have partially confirmed conclusions based on morphology but have also led to some unexpected results and have revealed a high level of cryptic diversity in some taxa (Rindi et al. 2004, 2007; Perez-Ortega et al. 2010). Most of the taxonomic and distributional information (as well as molecular data) currently available for the Prasiolales has been produced in the northern hemisphere, mainly because scientists interested in the systematics of this group are based primarily in northern geographical regions. In general, the information available for these algae in the southern hemisphere is much more limited, with the remarkable exception of Antarctic Prasiola crispa (Lightfoot) Ku ¨ tzing (which is one of the best-studied terrestrial algae from ecological and physiological perspectives; e.g., Hoyer et al. 2001; Kovacik & Batista Pereira 2001; Lud et al. 2001; Kosugi et al. 2010). Records of Prasiolales, particularly marine species, are available from several regions of the southern hemisphere (Womersley 1956, 1984; Ramı ´rez & Santelices 1991; Adams 1994; Boraso de Zaixso 2002). With few exceptions, however, the details reported on the biology of these organisms are limited. To date, relatively few * Corresponding author (f.rindi@univpm.it). Phycologia (2012) Volume 51 (1), 86–97 Published 31 January 2012 86