THE INFLUENCE OF ENVIRONMENTAL CHARACTERISTICS ON LIFE HISTORY ATTRIBUTES OF ANTARCTIC TERRESTRIAL BIOTA

摘要

Polar environments are conventionally regarded as harsh and inhospitable. Although north and south polar regions share many features, one important difference separates their ecology. Whilst the Arctic consists of the northern zones of large land masses surrounding a polar ocean with a thin ice covering, the Antarctic is a continental land mass, overlain by up to 4 km of ice and with the highest average altitude of any continent, surrounded by at least 1000 km of cold ocean. This difference drives atmospheric and oceanic circulations such that climatic conditions and their seasonal variations are markedly different at comparable latitudes in the two polar biomes. Nevertheless, on the basis of annual climatic data, it is possible to equate differentregions of the Arctic and Antarctic For consistency and ease of comparison between north and south polar regions, the qualifying terms 'cool', 'cold' and 'frigid' Antarctic/Arctic will be used throughout this review (sensu Longton, 1988). These equate respectively to the terms 'sub-', 'maritime' and 'continental', commonly used in publications on the Antarctic region. The definitions highlight the extent to which Antarctic latitudes are colder than their northern counterparts. For instance, the cold Arctic consists of the northern fringes of Ellesmere Island and its neighbours, Svalbard, Franz Josef Land, Novaya Zemlya and the New Siberian Islands, all in the region of 80-85° N, whereas the comparable cold (= maritime) Antarctic comprises the westernside of the Antarctic Peninsula and islands of the Scotia Arc (South Shetland, South Orkney and South Sandwich Islands), at only 55—68° S. Excepting these, the entire continent falls within the frigid (= continental) Antarctic. With mean monthly temperatures in this zone only rarely and locally exceeding o °C in summer, there are no comparable terrestrial ecosystems in the Arctic, although similar temperatures are experienced on the Greenland icecap and in the northern Arctic ocean .