Distinct community of plants which evolved on the supercontinent of Gondwana
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,
botanist
Ronald D'Oyley Good
identified a separate
Antarctic Floristic Kingdom
that included southern South America, New Zealand, and some southern island groups. In addition, Australia was determined to be its own
floristic kingdom
because of the influx of tropical Eurasian flora that had mostly supplanted the Antarctic flora and included
New Guinea
and New Caledonia in the
Paleotropical
floristic kingdom.
Origin
[
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]
Millions of years ago the climate in Antarctica was warmer, and was able to support flora well into the
Neogene
.
This included forests of
podocarps
and
southern beech
. Antarctica was also part of the ancient supercontinent of Gondwana, which gradually broke up by
plate tectonics
starting 110 million years ago. The separation of South America from Antarctica 30?35 million years ago allowed the
Antarctic Circumpolar Current
to form, which isolated Antarctica climatically and caused it to become much colder. The Antarctic flora subsequently died out in Antarctica, but is still an important component of the flora of southern
Neotropic
(South America) and
Australasian realms
, which were also former parts of Gondwana.
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
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.
Flora of Antarctica
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]
Antarctic palaeoflora
[
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]
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
.
During the colder
Neogene
(17?2.5 Ma), a low diversity
tundra
ecosystem dominated by angiosperms replaced the rainforests.
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
.
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).
Two other species are assigned to genera
Hedycaryoxylon
(
Monimiaceae
) and
Atherospermoxylon
(
Atherospermataceae
).
A fossil
water lily
,
Notonuphar
(similar to
Nuphar
in the extant family
Nympheaceae
), was described from
Eocene
-aged sediments on
Seymour Island
in 2017.
Present-day flora
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Antarctica's extant flora presently consists of around 250
lichens
, 100
mosses
, 25-30
liverworts
, and around 700 terrestrial and aquatic
algal
species. Species of moss
endemic
to Antarctica include
Grimmia antarctici
,
Schistidium antarctici
, and
Sarconeurum glaciale
. Just two native flowering plants,
Deschampsia antarctica
(Antarctic hair grass) and
Colobanthus quitensis
(Antarctic pearlwort), are found on the northern and western parts of the
Antarctic Peninsula
. The continent of Antarctica itself has been too cold and dry to support any other vascular plants for millions of years. The scanty vegetation of Antarctica is a result of the chilling temperature, lack of sunlight, little rainfall, relatively poor
soil quality
, and a lack of moisture due to the inability of the plants to absorb water in the form of ice.
See also
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]
References
[
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]
Works cited
[
edit
]
- Friis, Else M.; Iglesias, Ari; Reguero, Marcelo A.; Mors, Thomas (2017-08-01).
"Notonuphar antarctica, an extinct water lily (Nymphaeales) from the Eocene of Antarctica"
.
Plant Systematics and Evolution
.
303
(7): 969?980.
Bibcode
:
2017PSyEv.303..969F
.
doi
:
10.1007/s00606-017-1422-y
.
ISSN
2199-6881
.
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.
doi
:
10.1071/SB00022
.
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.
doi
:
10.1006/anbo.2001.1425
.
hdl
:
1874/31604
.
S2CID
86788384
.
- Rees-Owen, Rhian L.; Gill, Fiona L.; Newton, Robert J.; Ivanovi?, 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.
Bibcode
:
2018OrGeo.118....4R
.
doi
:
10.1016/j.orggeochem.2018.01.001
.
hdl
:
10023/12701
.
ISSN
0146-6380
.
S2CID
46651929
.
Further reading
[
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]
- Cox, C. Barry, Peter D. Moore (1985).
Biogeography: An Ecological and Evolutionary Approach (4th ed.)
. Blackwell Scientific Publications, Oxford.
External links
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]