Antarctic flora
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Antarctic flora are a distinct community of vascular plants which evolved millions of years ago on the supercontinent of Gondwana. Presently, species of Antarctica flora reside on several now separated areas of the Southern Hemisphere, including southern South America, southernmost Africa, New Zealand, Australia, and New Caledonia. Joseph Dalton Hooker (1817 – 1911) was the first to notice similarities in the flora and speculated that Antarctica had served as either a source or a transitional point, and that land masses now separated might formerly have been adjacent.[1]
Based on the similarities in their flora,
Origin
Millions of years ago the climate in Antarctica was warmer, and was able to support flora well into the
Some genera which originated in Antarctic Flora are still recognized as major components of New Caledonia, Tasmania, Madagascar, India, New Zealand, and southern South America.
South America, Madagascar, Africa, India, Australia, New Zealand, and Antarctica were all part of the supercontinent Gondwana, which started to break up in the early Cretaceous period (145–66 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 most resembled the flora of modern-day southern New Zealand. A drier northern Gondwanan flora had developed in northern South America and northern Africa.
Africa and India drifted north into the tropical latitudes, became hotter and drier, and ultimately connected with the Eurasian continent. 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
Flora of Antarctica
Antarctic palaeoflora
A wide variety of plant life has resided in Antarctica throughout its history. Investigations of Upper Cretaceous and Early Tertiary sediments of Antarctica yield a rich assemblage of well-preserved fossil dicotyledonous angiosperm wood which provides evidence for the existence, since the Late Cretaceous, of temperate forests similar in composition to those found in present-day southern South America, New Zealand and Australia. It is suggested a paleobotanical habitat similar to the extant cool temperate Valdivian rainforests.[3] During the colder Neogene (17–2.5 Ma), a low diversity tundra ecosystem dominated by angiosperms replaced the rainforests.[2]
There are two conifer and at least seven angiosperm morphotypes recorded in the Antarctica palaeoflora. Conifers include Cupressinoxylon, which is the more common, and Podocarpoxylon.[3] The angiosperm component includes two species of Nothofagoxylon, one species of Myrceugenelloxylon (similar to Luma, in the extant family Myrtaceae), and one species of Weinmannioxylon (similar to Eucryphia in the extant family Cunoniaceae).[3] Two other species are assigned to genera Hedycaryoxylon (Monimiaceae) and Atherospermoxylon (Atherospermataceae).[4] A fossil water lily, Notonuphar (similar to Nuphar in the extant family Nympheaceae), was described from Eocene-aged sediments on Seymour Island in 2017.[5]
Present-day flora
Antarctica's extant flora presently consists of around 250
See also
References
- ^ Hooker (1847), p. [page needed].
- ^ a b Rees-Owen et al. (2018).
- ^ a b c Poole (2001).
- ^ Poole & Gottwald (2001).
- ^ Friis et al. (2017).
Works cited
- Friis, Else M.; Iglesias, Ari; Reguero, Marcelo A.; Mörs, Thomas (2017-08-01). "Notonuphar antarctica, an extinct water lily (Nymphaeales) from the Eocene of Antarctica". Plant Systematics and Evolution. 303 (7): 969–980. S2CID 23846066.
- Poole, Imogen; Gottwald, Helmut (2001). "Monimiaceae sensu lato, an element of Gondwanan polar forests: Evidence from the late Cretaceous-early tertiary wood flora of Antarctica". Australian Systematic Botany. 14 (2): 207. ISSN 1030-1887.
- Hooker, J.D. (1847). The Botany of the Antarctic Voyage of H. M. Discovery Ships Erebus and Terror in the Years 1839-1843: Under the Command of Captain Sir James Clark Ross. Vol. 1, part 2. Reeve Brothers.
- Poole, I (2001). "A Fossil Wood Flora from King George Island: Ecological Implications for an Antarctic Eocene Vegetation". Annals of Botany. 88 (1): 33–54. S2CID 86788384.
- Rees-Owen, Rhian L.; Gill, Fiona L.; Newton, Robert J.; Ivanović, Ruza F.; Francis, Jane E.; Riding, James B.; Vane, Christopher H.; Lopes dos Santos, Raquel A. (2018). "The last forests on Antarctica: Reconstructing flora and temperature from the Neogene Sirius Group, Transantarctic Mountains". Organic Geochemistry. 118: 4–14. S2CID 46651929.
Further reading
- Cox, C. Barry, Peter D. Moore (1985). Biogeography: An Ecological and Evolutionary Approach (4th ed.). Blackwell Scientific Publications, Oxford.
External links
- Plants — Australian Antarctic Division
- Plants — British Antarctic Survey, Natural Environment Research Council
- The Plants of Antarctica, a blog by Caitlyn Bishop, Oceanwide Expeditions