A novel Antarctic microbial endolithic community within gypsum crusts

A novel endolithic microbial habitat is described from a climatically extreme site at Two Step Cliffs, Alexander Island, Antarctic Peninsula (71°54′S, 68°13′W). Small endolithic colonies (<3 mm in diameter) are found within the translucent gypsum crust that forms on the surface of sandstone boulders. Gypsum crusts are found on ice-free rocks throughout the Antarctic and therefore offer potential colonization sites at more inhospitable locations, including sites at higher latitudes. Cyanobacterial, bacterial and fungal components were cultured from the crust material and have been identified as Chloroglea sp., Sphingomonas sp. and Verticillium sp. respectively. A non-cultured, black-pigmented fungus was also found. Cyanobacterial primary productivity is low: at depths of 1.2 and 2.5 mm within the crust, estimates of possible cell divisions per year were < 38 and four respectively. This microniche is proposed to provide protection from desiccation, rapid temperature variation and UV radiation flux while allowing penetration of photosynthetically active radiation (PAR) for utilization by phototrophs. The endolithic communities are less extensive than those of the Dry Valleys, continental Antarctica, probably owing to only recent deglaciation (<7000 year ago)

A systematic survey of floral nectaries

The construction of classifications, as well as the understanding of biological diversity, depends upon a careful comparison of attributes of the organisms studied (Stuessy, 1990). It is widely known that data from diverse sources showing differences from taxon to taxon are of systematic significance. Dur-ing the 20th century, systematists have emphasized that their discipline involves a synthesis of all knowledge (Stevens, 1994) or, in other words, the variation of as many relevant characters as possible should be incorporated into the natural system to be constructed. The extent to which particular characters are constant or labile will determine their usefulness to syste-matics. In general, more conservative characters will be valuable in defining families and orders, whereas more labile characters may be useful at the ge-neric and specific levels (Webb, 1984). There is no doubt that floral characters are among the most used in the classification of flowering plants. At the same time, they constitute essential features in diagnostic keys to taxa in both taxonomic treatments and Floras (Cronquist, 1981, 1988).Fil: Bernardello, Gabriel Luis Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin