|
|
|
|
|
Antarctic FloraThe 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 (see Floristic province), 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 other floristic communities had mostly supplanted the Antarctic flora). South America, Africa, India, Australia, New Zealand, and Antarctica were all part of the Gondwana supercontinent, 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 a distinct Southern Gondwana flora by the late Cretaceous period, which resembles the New Zealand flora of today, in the cooler and humid southern hemisphere regions of Australia, southern South America, southern Africa, Antarctica, and New Zealand. A drier northern Gondwana flora had developed in northern South America and northern Africa. Africa and India drifted north, 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, 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, Cunoniaceae 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 (a grass and a small cushion-forming plant) are found on the northern and western parts of the Antarctic Peninsula.
|
 |
|
| Copyright 2005-2009 OnPedia.com. All Rights Reserved |
|
|