Kingdom Plantae Family Orchidaceae Tribe Diurideae Rank Genus | Order Asparagales Subfamily Orchidoideae Subtribe Drakaeinae | |
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Similar Arthrochilus, Rimacola, Odontorrhynchus | ||
Spiculaea ciliata, commonly known as elbow orchid, is the only species in the flowering plant genus Spiculaea in the orchid family, Orchidaceae and is endemic to the south-west of Western Australia. It is unusual in a number of respects, including that it grows in shallow soil on granite rock outcrops, grows and flowers in the hottest months of the year and has a unique method of using thynnid wasps as pollinators.
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Description
Spiculaea ciliata is a terrestrial, perennial, deciduous, sympodial herb with a few inconspicuous, fine roots and an oval-shaped tuber lacking a protective sheath. The tuber produces a replacement tuber and daughter tubers on the end of short, root-like stolons. There is a single stalked leaf about 2 cm (0.8 in) long, 1 cm (0.4 in) wide at the base of the plant and purplish on the lower surface. The leaf is fully developed before the first flowers appear but withers before the first flowers open in late October.
There are up to ten resupinate flowers on the end of a wiry stem 10–18 cm (4–7 in) high which is thickest near the top and which gradually withers from the base as the flowers mature. Each flower is straw-coloured, 20 mm (0.8 in) long and 10 mm (0.4 in) wide on a short stalk. The dorsal sepal curves over the top of the flower, with its side edges curved downwards. The two lateral sepals are shorter than the dorsal sepal and the two petals are narrower than both. The petals are sepals are separate from each other. As is usual in orchids, one petal is highly modified as the central labellum. The labellum is shaped like a wingless insect, and is attached to the base of the column by a flexible, hinge-like "claw". The labellum is much smaller than in other orchids and is rod-like, fleshy and has many club-shaped hairs. The sexual parts of the flower are fused to the column, which has wing-like structures on its sides. Flowering occurs from October to January and is followed by a fruit which is a non-fleshy, glabrous, dehiscent capsule containing a large number of seeds.
Taxonomy and naming
This orchid was first formally described in 1840 by John Lindley and the description was published in A Sketch of the Vegetation of the Swan River Colony. In 1871, Heinrich Reichenbach changed the name to Drakaea ciliata but in 1989, David Jones and Mark Clements reverted to Lindley's name.
The origin of the genus name, "Spiculaea", is unclear but spicula is a Latin word meaning "an ear of grain" and the specific epithet "ciliata" is a Latin word meaning "eyelash" or "eyelid".
Distribution and habitat
Spiculaea ciliata grows in shallow, sandy soil over granite between the Darling Scarp, Paynes Find and Mount Ney in the Avon Wheatbelt, Coolgardie, Esperance Plains, Geraldton Sandplains, Jarrah Forest and Mallee biogeographic regions.
Ecology
The flowers of elbow orchid have been described as "bizarre" and the production of flowers during the hottest months is unusual. One author described: "When most other plants dead or dying, this tiny orchid at its fascinating best. When everything else was brittle underfoot these are still succulent. A specimen continued to flower in my collection in the fridge after I got home, weeks later."
Spiculaea ciliata is thought to be pollinated by a male thynnid wasp of the genus Thynnoturneria which is initially attracted to the labellum of the orchid by a pheromone, flying from downwind towards the flower. At rest, the labellum resembles a wingless female wasp, resting on a blade of grass. The insect picks up the dummy females and tries to fly off with it, rising into the column where the column wings hold the insect, and its abdomen comes into contact with the sexual parts of the flower.
Conservation
Elbow orchid is classified as "Not Threatened" by the Western Australian Government Department of Parks and Wildlife.