Taxonomic studies of terrestrial yellow-green (Heterokontophyta, xanthophyceae) and green (Chlorophyta) algae from the Ross Sea regions, Antarctica

Abstract

Terrestrial xanthophycean and chlorophyte algae have been studied at widespread Antarctic localities. All published literature (1847 to 1998) is reviewed on chlorophyte and xanthophycean algae from terrestrial and non-marine aquatic habitats of Maritime and Continental Antarctica. A checklist of all terrestrial and freshwater algae has been compiled from all literature from 1847 to 1998. This has shown that their diversity is not fully known because of inadequacy of collections and analyses of samples. We still have insufficient base-line information about the morphological diversity of algae in Antarctica, and particularly Ross Sea regions. By detailed examination of cultured strains from the Ross Sea regions, the present study aims to contribute to the resolution of the following hypothesis: "The terrestrial algal flora of Antarctica does not comprise cosmopolitan species". The goals of the study were to: 1) provide detailed descriptions of the vegetative and reproductive characteristics of unknown, or previously poorly known, unicellular xanthophycean, and unicellular and filamentous chlorophyte algae using light and electron microscopy, 2) use isozymes to compare the genotypes of Antarctic Botrydiopsis and Chlorellidium strains with similar strains isolated from New Zealand and those in culture collections from Europe, and 3) investigate carotenoid pigments as taxonomic characters within Botrydiopsis and Chlorellidium. Each of 39 species (7 species in 3 genera from Xanthophyceae and 32 species in 14 genera from Chlorophyta) have been described and illustrated with camera lucida drawings and photomicrographs. There are 25 new records of chlorophyte and four new records of xanthophycean species for Antarctica. In addition, TEM has been used for the first time for 14 species. In three genera of Xanthophyceae and in Stichococcus TEM has revealed characteristics which are impossible to observe in sufficient detail by LM. The phenetic analysis on morphological data shows that Botrydiopsis and Chlorellidium exhibit wide morphological heterogeneity. Isozymes have not distinguished Botrydiopsis, Botryochloris and Chlorellidium. Pigment analysis has not revealed diversity at species level. Phenetic analysis of morphological data is not congruent with isozyme data and neither analysis is in agreement with the traditional system of classification. It is suggested that different techniques, e.g.18S rRNA gene sequencing should be used to examine present species concepts.