Nematoceras dienemum
Encyclopedia
Nematoceras dienemum , also known as the Windswept Helmet-orchid, is one of two helmet orchids endemic to Australia
’s subantarctic
Macquarie Island
, and the first orchid to be found there. It was discovered in 1978 and identified as Corybas macranthus, then split off and described by David Jones in 1993 as a new species, Corybas dienemus (from Greek
dienemos - “windswept”). In 2002 it was placed in the reinstated genus Nematoceras
.
es which float on a substrate of waterlogged
peat
with a water table
very close to the soil surface. The total known population comprises about 7500 plants.
ous, herbaceous plant
that forms clonal colonies
. The leaves are flattish, fleshy and solitary, dark green above and silvery-green underneath. The flower
is erect, nestling in the leaf base, green with purplish-red markings, 25–30 mm long and 20–25 mm wide. It can be distinguished from its congener and the only other orchid on the island, the Grooved Helmet-orchid Nematoceras sulcatum
, by its predominantly green flowers, compared with the predominantly dark red ones of N. sulcatum.
through the production of daughter root-tubers on lateral underground stolon
s. Its leaves die off in autumn, with new leaves emerging in spring. Although the life expectancy and age of sexual maturity of the orchid are unknown, it is likely that some clonal colonies have existed for several decades. The pollination method is unknown, though one possible pollinator is the Black Fungus Gnat (Bradysia watsoni), which is common on the coastal terraces where the orchid is found.
, a World Heritage Site
and a UNESCO
Biosphere Reserve. However, the Windswept Helmet-orchid is listed as endangered on the Tasmanian Threatened Species Protection Act 1995 because of its restricted distribution, small population and projected decline through ongoing habitat degradation caused by the grazing, digging and burrowing activities of rabbit
s. Additional threats are the formation of seal
wallows and, potentially, climate change
. It is also listed as Critically Endangered
under Australia's Environment Protection and Biodiversity Conservation Act 1999
.
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
’s subantarctic
Subantarctic
The Subantarctic is a region in the southern hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° – 60° south of the Equator. The subantarctic region includes many islands in the southern parts of the Indian Ocean, Atlantic Ocean and...
Macquarie Island
Macquarie Island
Macquarie Island lies in the southwest corner of the Pacific Ocean, about half-way between New Zealand and Antarctica, at 54°30S, 158°57E. Politically, it has formed part of the Australian state of Tasmania since 1900 and became a Tasmanian State Reserve in 1978. In 1997 it became a world heritage...
, and the first orchid to be found there. It was discovered in 1978 and identified as Corybas macranthus, then split off and described by David Jones in 1993 as a new species, Corybas dienemus (from Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
dienemos - “windswept”). In 2002 it was placed in the reinstated genus Nematoceras
Nematoceras
Nematoceras is a genus of orchids , sometimes known as spider orchids, helmet orchids or spidery helmet-orchids, found mainly in New Zealand and its subantarctic islands, with two species on Australia’s Macquarie Island...
.
Distribution and habitat
The orchid is known from ten sites on the northern half of Macquarie Island, where it inhabits the lower coastal terraces, not more than 30 m above sea level, where the vegetation is dominated by mossMoss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
es which float on a substrate of waterlogged
Waterlogging (agriculture)
Waterlogging refers to the saturation of soil with water. Soil may be regarded as waterlogged when the water table of the groundwater is too high to conveniently permit an anticipated activity, like agriculture....
peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
with a water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...
very close to the soil surface. The total known population comprises about 7500 plants.
Description
The orchid is a small (30–50 mm tall), terrestrial, tuberTuber
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction...
ous, herbaceous plant
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
that forms clonal colonies
Clonal colony
A clonal colony or genet is a group of genetically identical individuals that have grown in a given location, all originating vegetatively from a single ancestor. In plants, an individual in such a population is referred to as a ramet...
. The leaves are flattish, fleshy and solitary, dark green above and silvery-green underneath. The flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
is erect, nestling in the leaf base, green with purplish-red markings, 25–30 mm long and 20–25 mm wide. It can be distinguished from its congener and the only other orchid on the island, the Grooved Helmet-orchid Nematoceras sulcatum
Nematoceras sulcatum
Nematoceras sulcatum, also known as the Grooved Helmet-orchid, is one of two helmet orchids endemic to Australia’s subantarctic Macquarie Island, and the second to be discovered. The specific epithet comes from the Latin sulcatus – “grooved”, with reference to the prominent groove in the labellum...
, by its predominantly green flowers, compared with the predominantly dark red ones of N. sulcatum.
Reproduction
The flowering period of the orchid is from November to January. It produces seeds annually but also reproduces vegetativelyVegetative reproduction
Vegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...
through the production of daughter root-tubers on lateral underground stolon
Stolon
In biology, stolons are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons.-In botany:...
s. Its leaves die off in autumn, with new leaves emerging in spring. Although the life expectancy and age of sexual maturity of the orchid are unknown, it is likely that some clonal colonies have existed for several decades. The pollination method is unknown, though one possible pollinator is the Black Fungus Gnat (Bradysia watsoni), which is common on the coastal terraces where the orchid is found.
Conservation status
Macquarie Island is a nature reserveNature reserve
A nature reserve is a protected area of importance for wildlife, flora, fauna or features of geological or other special interest, which is reserved and managed for conservation and to provide special opportunities for study or research...
, a World Heritage Site
World Heritage Site
A UNESCO World Heritage Site is a place that is listed by the UNESCO as of special cultural or physical significance...
and a UNESCO
UNESCO
The United Nations Educational, Scientific and Cultural Organization is a specialized agency of the United Nations...
Biosphere Reserve. However, the Windswept Helmet-orchid is listed as endangered on the Tasmanian Threatened Species Protection Act 1995 because of its restricted distribution, small population and projected decline through ongoing habitat degradation caused by the grazing, digging and burrowing activities of rabbit
Rabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...
s. Additional threats are the formation of seal
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
wallows and, potentially, climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
. It is also listed as Critically Endangered
Critically Endangered
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....
under Australia's Environment Protection and Biodiversity Conservation Act 1999
Environment Protection and Biodiversity Conservation Act 1999
The Environment Protection and Biodiversity Conservation Act 1999 is an Act of the Parliament of Australia that provides a framework for protection of the Australian environment, including its biodiversity and its natural and culturally significant places...
.