The Role of Lichens in Antarctic Ecosystems

Abstract

Antarctic terrestrial ecosystems can be divided into two main series: those of continental Antarctica and those of the maritime Antarctic. Within the former series, plant exist as isolated groupings of plants growing under a severe continental polar-desert climate and appear to be similar to communities of the High Arctic (e.g. the interior plateau of Devon Island). Communities in the maritime Antarctic region are more diverse, with less severe environmental conditions, and show affinities with lichen com- munities occupying similar habitats in boreal-Arctic zones of the northern hemisphere. Roles played by lichens in the two series of ecosystems are influenced considerably by environmental conditions and in continental Antarctica are often completely subordinated to physical processes. Weathering of substrata, for instance, in continental Antarctica, consists of the operation of several physical processes with lichens playing an insignificant role. It is only in the more suitable habitats found in the maritime Antarctic that lichens are able to play their full role in the development and functioning of ecosystems. The Antarctic regions present some of the most severe environmental conditions endured by plant life, involving habitats characterized by intense cold, physiological drought and seasonal limitation of insolation. Such conditions severely limit the range of life forms found in these regions. Compared with the Arctic, the Antarctic presents a series of terrestrial ecosystems characterized by a greatly reduced flora and fauna, isolated from other systems by extensive ocean barriers. These Antarctic ecosystems have thus been defined as being relatively simple, in which physical processes often dominate and subordinate biotic factors in the development and functioning of com- munities. Unlike the Arctic, vascular plants are scarce, being represented by only two species in the Antarctic Peninsula region. A second major difference is the almost complete lack of herbivores, vertebrate grazers being absent. Antarctic terrestrial eco- systems are thus rendered unique in that they are dominated by cryptogamic plants and invertebrate animals. Lichens are the most prominent macroscopic plants in terms of species, distribution and biomass, but before their roles can be outlined it is nec- essary to briefly describe the ecosystems present, a general review of which has been