THE MARINE AND TERRESTRIAL PRASIOLALES (CHLOROPHYTA) OF GALWAY CITY, IRELAND: A MORPHOLOGICAL AND ECOLOGICAL STUDY

Green algae belonging to the order Prasiolales have been reported frequently in terrestrial, freshwater, and marine habitats, generally in situations in which they are not submerged continuously and often in association with deposits of avian feces or other rich sources of nitrogenous compounds. Terrestrial habitats in Galway City on the west coast of Ireland have large populations of four such algae: Rosenvingiella polyrhiza (Rosenvinge) P. C. Silva, Prasiola calophylla (Carmichael ex Greville) Kützing, P. crispa (Lightfoot) Kützing, and P. stipitata Suhr ex Jessen, of which only the last is in any way fully associated with a tidal regime. The other species are found in an extraordinary range of nonmarine terrestrial habitats in the center of Galway, a city that still retains its narrow, medieval street plan. Width of the streets, proportion of residences, substratum type, and aspect are shown to be the main factors affecting the distribution of these algae, although a combination of consistent dampness and nitrogenous-compound availability from animal wastes is likely to be the primary determining factor. Morphological and phenological data are presented for each entity, and it is concluded from field observations that R. polyrhiza should continue to be recognized as a separate entity, even though a close relationship with Schizogonium murale Kützing is probable.     

MOLECULAR PHYLOGENY OF THE GREEN ALGAL ORDER PRASIOLALES (TREBOUXIOPHYCEAE,CHLOROPHYTA)1

The systematics of the Prasiolales was investigated by phylogenetic inference based on analyses of the rbcL and 18S rRNA genes for representatives of all four genera currently attributed to this order (Prasiococcus, Prasiola, Prasiolopsis, Rosenvingiella), including all type species. The rbcL gene had higher sequence divergence than the 18S rRNA gene and was more useful for phylogenetic inference at the ranks of genus and species. In the rbcL gene phylogeny, three main clades were observed, corresponding to Prasiola, Prasiolopsis, and Rosenvingiella. Prasiococcus was nested among species of Prasiola occurring in subaerial and supralittoral habitats. Trichophilus welckeri Weber Bosse, a subaerial alga occurring in the fur of sloths in Amazonia, was closely related to Prasiolopsis ramosa Vischer. The species of Prasiola were grouped into three well‐supported clades comprising (i) marine species, (ii) freshwater and terrestrial species with linear blades, and (iii) terrestrial species with rounded or fan‐shaped blades. Sequence divergence was unexpectedly low in the marine group, which included species with different morphologies. For the 18S rRNA gene, the phylogenetic analyses produced several clades observed for the rbcL gene sequence analysis, but, due to very little sequence variation, it showed considerably lower resolution for inference at the species and genus levels. Due to the low support of some internal branches, the results of the analyses did not allow an unambiguous clarification of the origin and the early evolution of the Prasiolales.     

Prasionema heeschiae sp. nov. (Prasiolales,Chlorophyta) from Campbell Island,New Zealand: first record of Prasionema in the southern hemisphere

A new species in the genus Prasionema (Prasiolales, Trebouxiophyceae) is described from Campbell Island, in the New Zealand subantarctic region, the first record of this genus in the southern hemisphere. Prasionema heeschiae sp. nov. is filamentous, uni- to predominantly biseriate, with disc-shaped cells, and an axial plastid with a central pyrenoid. It is anchored by an enlarged pigmented basal cell. There is evidence of reproduction by both spores and fragmentation. This species was found growing on a timber wharf above the high tide level. The only other species in the genus, P. payeri Heesch, M.Pazoutová & Rindi, was described from Spitzbergen growing on soil in a high nutrient environment. The bipolar distribution of Prasionema is discussed. Based on phylogenetic analyses that included sequence data from holotype material of southern filamentous Prasiolales, we reduce Rosenvingiella australis to synonymy with R. tasmanica.     

THE PRASIOLALES (CHLOROPHYTA) OF ATLANTIC EUROPE: AN ASSESSMENT BASED ON MORPHOLOGICAL,MOLECULAR, AND ECOLOGICAL DATA,INCLUDING THE CHARACTERIZATION OF ROSENVINGIELLA RADICANS (KÜTZING) COMB. NOV.1

Despite a simple morphology and intensive studies carried out for more than two centuries, the systematics of the Prasiolales still presents several unsolved problems. The taxonomic relationships of several common species of Prasiolales, mostly from northern Europe, were investigated by a combination of morphological observations, culture experiments, and molecular analyses based on rbcL sequences. The results indicate that Rosenvingiella and Prasiola are separate genera. The capacity for production of tridimensional pluriseriate gametangia and the presence of unicellular rhizoids are the morphological features that discriminate Rosenvingiella from filamentous forms of Prasiola. The molecular data indicate that uniseriate filaments can be produced in at least three different species of Prasiola. The genetic diversity of uniseriate filamentous Prasiolales is higher than their simple morphology would indicate, and the provisional retention of Schizogonium Kützing 1843 as independent genus is recommended. The rbcL phylogeny confirms that Prasiola calophylla, P. crispa, and P. stipitata are distinct species, whereas P. stipitata and P. meridionalis are probably conspecific. Rosenvingiella polyrhiza is a strictly marine alga, and most records of Rosenvingiella in Europe are referable to Rosenvingiella radicans, proposed here as a new combination based on Ulothrix radicans Kützing 1849 . This is a primarily terrestrial alga that can occur from upper intertidal rock to locations situated hundreds of kilometers inland. The great confusion that has arisen in Europe between these two species in the last century is mostly due to misidentifications of marine populations of R. radicans.