Megatrabs ( English megaherbs ) is the collective name of herbaceous plants growing on the New Zealand subantarctic islands ( Campbell Island, Auckland Island ), the Australian island of Macquarie and other islands of the subantarctic zone [1] . These plants, perfectly adapted to the extreme subantarctic climate and acid soil of the islands, are distinguished by large leaves and characteristic colors [1] . In places of their growth, the temperature is from 0 to +15 ° C, high humidity, strong winds, constant cloudiness. Megatrabs are able to bloom annually, but three-year development cycles are more characteristic.
Content
History
Megatraves were first discovered by participants in an expedition to Antarctica in 1839-1843, when the expedition stopped on the subarctic islands along the route. Expedition captain James Clark Ross named these plants Megaherb . The botanist Joseph Hooker pointed out that these herbs are not ordinary plants, their flowers are similar to the flowers of plants growing in the tropics .
In the XIX-XX centuries, cattle brought by Europeans systematically exterminated island plants. Only a complete ban on cattle breeding saved them from extinction; after the export of animals from the New Zealand islands (1987-1993), megatrava populations recovered over several years. In the New Zealand islands, their collection is prohibited; the only legally assembled collection grows in the Invercargill Botanical Garden . Outside the islands, in other climatic conditions, these plants take root poorly.
Composition
Megatrabs are not related plants; they include representatives of various families to megatrabs [1] :
- Anisotome latifolia (Campbell Island) - Umbrella family;
- Bulbinella rossii (New Zealand Subantarctic Islands) - Xanthorrhoeae family ;
- Damnamenia vernicosa (New Zealand subantarctic islands) - Astrov family ;
- Pringlea antiscorbutica - Kerguelen cabbage (Kerguelen, Crozet , Prince Edward , Heard and MacDonald islands) - Cabbage family [1] ;
- Three species of the genus Pleurophyllum (New Zealand sub-Antarctic islands and Macquarie island) - the Astrov family [1] ;
- Stilbocarpa polaris (Macquarie Island) - Araliev family [1] .
Pink Anisotome latifolia Flowers
Hybrid Pleurophyllum speciosum and Pleurophyllum hookeri
Flowers Stilbocarpa polaris
In front of Pleurophyllum hookeri , behind Bulbinella rossii
Pleurophyllum speciosum
Megatrabs coexist with the “usual” perennial grasses Poa foliosa , Poa littorosa (Macquarie Island) and Poa flabellata ( South Georgia ). In island conditions, these herbs also reach “gigantic” sizes, forming pillows up to 2 m high [1] .
Morphological features
Megatrabs combine properties that are considered to be mutually exclusive in ordinary, continental, plants: on the one hand, broad leaves and fleshy rhizomes, in which plants accumulate nutrients, as well as relatively large seed sizes, on the other, a huge number of these seeds and high density insemination of the territory [1] . For 35 days Stilbocarpa polaris produces more than 10 thousand seeds per square meter of territory, Kerguelen cabbage - 150 thousand seeds per square meter per season [1] . All subantarctic plants, not only megatrabs, are characterized by the predominance of sexual reproduction over vegetative, which is unpromising under local conditions [2] .
These properties, on the one hand, are ideally suited to local fertile soils and climates with practically constant winds , constant cloud cover and the absence of direct insolation . On the other hand, such a combination is viable only in the absence of herbivorous animals. For example, on Macquarie Island, rats introduced by Europeans destroy up to 80% of Pleurophyllum hookeri peduncles, thereby preventing natural insemination [1] .
Notes
- ↑ 1 2 3 4 5 6 7 8 9 10 Convey, P. et al. Life History Traits // Trends in Antarctic Terrestrial and Limnetic Ecosystems: Antarctica as a Global Indicator / ed. Bergstrom, D. et al .. - Springer, 2007 .-- P. 107. - ISBN 9781402052774 .
- ↑ Convey, P. et al. Life History Traits, p. 108.
See also
- Island gigantism of animals and plants