Four **Achnanthidium** species (Bacillariophyta) formerly identified as **Achnanthidium minutissimum** from the Antarctic Region

Four taxa belonging to the complex of species around Achnanthidium minutissimum were found during the ongoing taxonomic revision of the Antarctic freshwater and limno-terrestrial diatom flora. Two taxa were previously described as Achnanthidium lailae and A. sieminskae. Two others were formerly identified as A. minutissimum but detailed light and scanning electron microscopical observations revealed sufficient morphological differences compared to the type of A. minutissimum, to justify their separation and description as new taxa: Achnanthidium indistinctum and A. maritimo-antarcticum. The morphology and ecology of all four taxa are discussed comparing the species with morphologically similar taxa. The biogeographical consequences of the splitting of the former A. minutissimum complex in the Antarctic Region are discussed.<br /

Moss-inhabiting diatoms from two contrasting Maritime Antarctic islands

Background and aims - The Maritime Antarctic vegetation is a poorly developed tundra dominated by lichens and mosses, mostly present in moist environments, providing a favourable habitat for microorganisms. Although, diatoms represent one of the most common algal groups in the Antarctic region, moss-inhabiting diatoms are rarely studied. The moss vegetation on islands in the Maritime Antarctic region forms a favorable habitat for non-marine diatoms. These moss-inhabiting diatom communities are of particular interest as little is known about their species composition, ecological preferences and habitats. The present paper discusses the diversity of moss inhabiting diatoms from Byers Peninsula (Livingston Island) and Ulu Peninsula (James Ross Island), Maritime Antarctic region.Methods - The composition of the moss inhabiting diatom flora of 84 samples collected from Byers Peninsula, Livingston Island and Lagoons Mesa area, James Ross Island has been studied using light microscopy.Key results - A total of 130 taxa, belonging to 39 genera has been recorded. Detrended Correspondence Analysis using the entire sample set clearly separates the James Ross Island (JRI) communities from the Livingston Island (LI) communities showing mostly the dominance of taxa preferring terrestrial (JRI) instead of more moist and aquatic conditions (LI). A Principal Component Analysis of only the Livingston Island samples formed three groups clearly separated by their diatom species composition. Although some taxa seem to occur in high abundances in several assemblages, a number of taxa showed a distinct preference for a particular assemblage. Biotic stress caused by marine birds and mammals, expressed in higher nutrient and salinity levels, seems to play a key role in determining the species composition.Conclusions - Our results showed clearly the presence of a well developed moss-inhabiting diatom flora on both studied localities. The composition of the studied communities is determined by the type of habitat, moisture and biotic influences (salinity and nutrients)

Three new araphid diatoms (Bacillariophyta) from the Maritime Antarctic Region

FIGURES 52–76: Staurosirella frigida Van de Vijver & E.Morales sp. nov. All pictures taken from the holotype population (sample BY047). Figs 52–69. LM images. Fig. 69 shows a girdle view whereas Figs 52–68 show valve views. Figs 70–76: SEM images. Fig. 70: External view of an entire valve showing the linking spines, the striae and part of the girdle. Fig. 71: Entire frustule linked to another valve showing the linking spines, parts of the girdle bands and the mantle. Fig. 72: Detail of the apical pore field at the foot pole, separated from the striae. Fig. 73: Detail of the apical pore field at the head pole showing 2 rows of small, rounded poroids. Fig. 74: Detail of the slit-like areolae. Fig. 75: Internal view of an entire valve. Fig. 76: Valvocopula with the fimbriate edges. Scale bar represents 10 µm except for Figs 72–74 where scale bar = 1µm.Published as part of Vijver, Bart Van De, Morales, Eduardo A. & Kopalová, Kateřina, 2014, Three new araphid diatoms (Bacillariophyta) from the Maritime Antarctic Region, pp. 256-266 in Phytotaxa 167 (3) on page 262, DOI: 10.11646/phytotaxa.167.3.4, http://zenodo.org/record/513882