''Genoplesium rhyoliticum'', commonly known as the Pambula midge-orchid or rhyolite midge orchid and as ''Corunastylis rhyolitica'' in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, is a species of

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. Orchids are cosmopolitan plants that are found in almost every habitat on Eart ...

endemic Endemism is the state of a species being found only 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 foun ...

New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

. It is a small orchid with up to eighteen dark, purplish-black flowers and is only known from six sites on the south coast where it grows in shallow soil over

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...

Description

''Genoplesium rhyoliticum'' is a terrestrial,

perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...

deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...

herb Herbs are a widely distributed and widespread group of plants, excluding vegetables, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal purposes, or for fragrances. Culinary use typically distingu ...

with an underground

tuber Tubers are a type of enlarged structure that plants use as storage organs for nutrients, derived from stems or roots. Tubers help plants perennate (survive winter or dry months), provide energy and nutrients, and are a means of asexual reproduc ...

and a single thin leaf long and fused to the flowering stem with the free part long. Between five and eighteen dark purplish-black flowers are crowded along a flowering stem long and taller than the leaf. The flowers are about long and wide and as with others in the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

, are inverted so that the labellum is above the

column A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member ...

rather than below it. The

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...

is narrow egg-shaped, about long and wide, with dark bands and hairless edges. The

lateral Lateral is a geometric term of location which may also refer to: Biology and healthcare * Lateral (anatomy), a term of location meaning "towards the side" * Lateral cricoarytenoid muscle, an intrinsic muscle of the larynx * Lateral release ( ...

sepals are linear to lance-shaped, about long, wide, and nearly parallel to each other. The

petal Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...

s are narrow egg-shaped, about long and wide with a pointed tip and sometimes a few hairs on the edges. The labellum is egg-shaped with the narrower end towards the base, long and wide with coarse hairs along its edges. There is a narrow triangular

callus A callus (: calluses) is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, b ...

in the centre of the labellum and extending almost to its tip. Flowering occurs in December and January.

Taxonomy and naming

''Genoplesium rhyoliticum'' was first described in 1991 by David Jones and Mark Clements from a specimen collected near

Pambula Pambula is a town in Bega Valley Shire on the far south coast of New South Wales, Australia south of Sydney via the Princes Highway. At the , Pambula had a population of 970 people. History The area was populated by the Thaua Aboriginal people ...

and the description was published in ''Australian orchid Research''. In 2002 Jones and Clements changed the name to ''Corunastylis rhyolitica''. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

(''rhyoliticum'') refers to the rock type on which this orchid grows.

Distribution and habitat

The Pambula midge-orchid usually grows in very shallow soil over rhyolite without shrubs or trees, but sometimes under shrubs in heath. It only occurs in six sites near Pambula.

Conservation

Of the six populations of ''G. rhyoliticum'', three occur in the

South East Forests National Park The South East Forests National Park is a national park located in between the Monaro (New South Wales), Monaro and South Coast (New South Wales), South Coast regions of New South Wales, Australia. The national park is situated southwest of Syd ...

and the only known threat to the species is grazing by native mammals. The species is listed as "Endangered" under the New South Wales ''Threatened Species Conservation Act'' and the Commonwealth Government ''

Environment Protection and Biodiversity Conservation Act 1999 The ''Environment Protection and Biodiversity Conservation Act 1999'' (Cth) 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 cult ...

'' (EPBC) Act.

References

External links

* * {{Taxonbar, from=Q15465671 rhyoliticum Orchids of New South Wales Endemic orchids of Australia Plants described in 1989