Canberra spider orchid
Caladenia actensis growing on Mount Majura in the ACT
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Diurideae
Genus: Caladenia
Species:
C. actensis
Binomial name
Caladenia actensis
Synonyms[1]

Arachnorchis actensis (D.L.Jones & M.A.Clem.) D.L.Jones & M.A.Clem.

Caladenia actensis, commonly known as the Canberra spider orchid,[2] is a plant in the orchid family Orchidaceae and is endemic to the Australian Capital Territory. It has a single leaf and usually only one greenish flower with red markings and only occurs in three small populations.

Description

Caladenia actensis is a terrestrial, perennial, deciduous, herb with an underground tuber and which grows singly or in small groups. A single leaf, 40–90 mm (2–4 in) long and 6–8 mm (0.2–0.3 in) wide appears in late autumn or early winter, after rain. Usually only a single flower is borne on a stalk 80–140 mm (3–6 in) tall. The flower is greenish, heavily marked with reddish-crimson lines and blotches, and is 12–20 mm (0.5–0.8 in) wide. The dorsal sepal is erect, 15–25 mm (0.6–1 in) long and about 2 mm (0.08 in) wide while the lateral sepals are a similar size but are turned downwards, close to the ovary. The petals are 10–15 mm (0.4–0.6 in) long and 2–3 mm (0.08–0.1 in) wide. The labellum is heart-shaped, 9–12 mm (0.4–0.5 in) wide and 8–10 mm (0.3–0.4 in) wide and maroon or green with a maroon tip. The labellum curves forward and downwards and there are up to six pairs of short, blunt teeth on its sides. The mid-line of the labellum has four to six rows of crowded dark, purplish-red calli. Flowering occurs from late September to mid- October.[2][3][4]

Taxonomy and naming

Caladenia actensis was first formally described by David L. Jones and Mark Clements in 1999 and the description was published in The Orchadian from a specimen collected on Mount Ainslie.[5] The specific epithet (actensis) is derived from the abbreviation of Australian Capital Territory (act) with the Latin ending "-ensis" meaning "of" or "in",[6] hence "of the Australian Capital Territory".

Distribution and habitat

Canberra spider orchid occurs in three small scattered populations on Mount Majura, Mount Ainslie and in the Madura Valley. It grows in the transitional zone between woodland and forest, with grasses and small shrubs, often amongst rocks.[2][3][4]

Ecology

As with other caladenias, this orchid requires a mycorrhizal association, in this case with the fungus Sebacina vermifera and is probably pollinated by a thynnid wasp.[4]

Conservation

Caladenia actensis is listed as "critically endangered" (CR) under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The main threats to the species include trampling by walkers, bicycles or horses, infrastructure building and maintenance, and weed invasion.[3]

References

  1. 1 2 "Caladenia actensis". Australian Plant Census. Retrieved 27 October 2023.
  2. 1 2 3 Jones, David L. (2006). A complete guide to native orchids of Australia including the island territories. Frenchs Forest, N.S.W.: New Holland. p. 95. ISBN 1877069124.
  3. 1 2 3 Frawley, Kevin. "Recovery Plan For Canberra Spider Orchid (Arachnorchis actensis)" (PDF). Australian Government Department of the Environment. Retrieved 24 January 2017.
  4. 1 2 3 "Canberra spider orchid Caladenia actensis - Action Plan" (PDF). ACT Government Environment, Planning and Sustainable Development Directorate - Environment. Retrieved 2 November 2020.
  5. ↑ "Caladenia actensis". APNI. Retrieved 24 January 2017.
  6. ↑ Brown, Roland Wilbur (1956). The Composition of Scientific Words. Washington, D.C.: Smithsonian Institution Press. p. 28.
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