Nematoceras dienemum
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''Corybas dienemus'', commonly known as the windswept helmet-orchid, is one of two helmet
orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowering ...
s
endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
to
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
's subantarctic Macquarie Island, and the first orchid to be found there. It is a relatively small orchid with green flowers with purplish-red markings and was discovered in 1978.


Description

The windswept helmet-orchid is a relatively small (30–50 mm tall), terrestrial,
tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing ...
ous,
herbaceous plant Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...
that forms clonal colonies. The leaves are flattish, fleshy and solitary, dark green above and silvery-green underneath. The
flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...
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 '' Corybas sulcatus'', by its predominantly green flowers, compared with the predominantly dark red ones of ''C. sulcatus''.


Taxonomy and naming

This orchid was first discovered on Macquarie Island in 1978 and identified as ''Corybas macranthus'', which is widespread in
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
. It was then recognised in 1993 by David Jones as a new species that he named '' Corybas dienemus''. In 2002, it was transferred to the reinstated genus '' Nematoceras'' as ''Nematoceras dienemum'' but that name has not been accepted by
World Checklist of Selected Plant Families The World Checklist of Selected Plant Families (usually abbreviated to WCSP) is an "international collaborative programme that provides the latest peer reviewed and published opinions on the accepted scientific names and synonyms of selected plan ...
at
Royal Botanic Gardens, Kew Royal Botanic Gardens, Kew is a non-departmental public body in the United Kingdom sponsored by the Department for Environment, Food and Rural Affairs. An internationally important botanical research and education institution, it employs 1,100 ...
. The
specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
(dienemum) is an
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
word meaning "windswept".


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
moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...
es that float on a substrate of waterlogged
peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficien ...
with a
water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...
very close to the soil surface. The total known population comprises about 7500 plants.


Reproduction

The flowering period of the orchid is from November to January. It produces seeds annually but also reproduces vegetatively through the production of daughter root-tubers on lateral underground
stolon In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...
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

Macquarie Island is a
nature reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, or features of geological or ...
, a
World Heritage Site A World Heritage Site is a landmark or area with legal protection by an international convention administered by the United Nations Educational, Scientific and Cultural Organization (UNESCO). World Heritage Sites are designated by UNESCO for h ...
and a
UNESCO The United Nations Educational, Scientific and Cultural Organization is a specialized agency of the United Nations (UN) aimed at promoting world peace and security through international cooperation in education, arts, sciences and culture. It ...
Biosphere Reserve. However, the windswept helmet-orchid is listed as
endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...
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 Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit speci ...
s. Additional threats are the formation of seal wallows and, potentially,
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
. It is also listed as Critically Endangered under Australia's Environment Protection and Biodiversity Conservation Act 1999. In 2010, a plan to eliminate rabbits from Macquarie Island was implemented and aerial baiting was commenced. Later, hunters and dog handlers destroyed a few surviving rabbits and by 2014, rabbits had been eliminated from the island.


References

{{Taxonbar, from=Q6991003 Endemic orchids of Australia Flora of Macquarie Island Plants described in 1993 dienemus