Antarctic flora

From Wikipedia, the free encyclopedia

Nothofagus fusca, New Zealand

The Antarctic flora is a distinct community of vascular plants which evolved millions of years ago on the supercontinent of Gondwana, and is now found on several separate areas of the Southern Hemisphere, including southern South America, southernmost Africa, New Zealand, Australia and Tasmania, and New Caledonia. Based on the similarities in their flora, botanist Ronald Good identified a separate Antarctic Floristic Kingdom, that included southern South America, New Zealand, and some southern island groups. Good identified Australia as its own floristic kingdom, and included New Guinea and New Caledonia in the Paleotropical floristic kingdom, because of the influx of tropical Eurasian flora that had mostly supplanted the Antarctic flora.

South America, Africa, India, Australia, New Zealand, and Antarctica were all part of the supercontinent Gondwana, which started to break up in the early Cretaceous period (135-65 million years ago). India was the first to break away, followed by Africa, and then New Zealand, which started to drift north. By the end of the Cretaceous, South America and Australia were still joined to Antarctica. Paleontologist Gilbert Brenner identified the emergence of a distinct southern Gondwanan flora by the late Cretaceous period in the cooler and humid southern hemisphere regions of Australia, southern South America, southern Africa, Antarctica, and New Zealand; it best resembled the flora of modern-day southern New Zealand. A drier northern Gondwanan flora had developed in northern South America and northern Africa.

Image:Nothofagus antarctica D.jpg

Nothofagus antarctica, Chile and Argentina

Africa and India drifted north into the tropical latitudes, became hotter and drier, and ultimately connected with the Eurasian continent, and today the flora of Africa and India have few remnants of the Antarctic flora. Australia drifted north and became drier as well; the humid Antarctic flora retreated to the east coast and Tasmania, while the rest of Australia became dominated by Acacia, Eucalyptus, and Casuarina, as well as xeric shrubs and grasses. Humans arrived in Australia 50-60,000 years ago, and used fire to reshape the vegetation of the continent; as a result, the Antarctic flora (also known as the Rainforest flora in Australia) retreated to a few isolated areas composing less than 2% of Australia's land area.

The woody plants of the Antarctic flora include conifers in the families Podocarpaceae, Araucariaceae and the subfamily Callitroideae of Cupressaceae, and angiosperms such as the families Proteaceae, Griseliniaceae, Cunoniaceae, Atherospermataceae, and Winteraceae, and genera like southern beech (Nothofagus) and fuchsia (Fuchsia). Many other families of flowering plants and ferns, including the tree fern Dicksonia, are characteristic of the Antarctic flora.

The continent of Antarctica itself has been too cold and dry to support virtually any vascular plants for millions of years, and its flora presently consists of around 250 lichens, 100 mosses, 25-30 liverworts, around 700 terrestrial and aquatic algal species. Two flowering plants, Deschampsia antarctica (Antarctic hair grass) and Colobanthus quitensis (Antarctic pearlwort), are found on the northern and western parts of the Antarctic Peninsula. Species of moss endemic to Antarctica include Grimmia antarctici, Schistidium antarctici, and Sarconeurum glaciale.