Calochilus, commonly known as beard orchids, is a genus of approximately 30 species of terrestrial orchids in the family Orchidaceae (order Asparagales). The genus was first formally described by the botanist Robert Brown in 1810 in his Prodromus Florae Novae Hollandiae, based on two Australian species.
Beard orchids are perennial, deciduous, sympodial herbs that grow from a pair of egg-shaped tubers. Each plant produces a single linear, fleshy, channelled leaf — or in some species no leaf at all — arising from the base of the flowering stem. The inflorescence is a raceme of one to many resupinate flowers. The most distinctive feature of the genus is the labellum: oblong near its base and triangular toward the tip, it is densely clothed in purple or metallic-coloured hairs that increase in length from base to tip, giving the flowers their striking "bearded" appearance. The dorsal sepal forms a broad hood over the column, and the petals are shorter and narrower than the sepals, often with a hook-like tip. The column is short and broad with prominent wings, and its base forms two rounded, eye-like collars around the stigma.
Most species are native to Australia, where the genus occurs in every state, but the group also extends to New Zealand, New Guinea, and New Caledonia, where one species is endemic. Habitats range from forest, woodland, heath, and wet swamps in temperate regions to grassy tropical wetlands and, in New Caledonia, maquis shrubland on rocky soils.
Unlike many other Australian terrestrial orchids, Calochilus species do not produce daughter tubers for vegetative reproduction. Pollination is performed by male Campsomeris wasps that are deceived into attempting to copulate with the hairy labellum while collecting pollinia; where cross-pollination does not occur, the anther is positioned directly above the stigma so that the pollinia fall or crumple onto it, enabling self-pollination.
Etymology
The genus name Calochilus is derived from the ancient Greek words kalos (καλός), meaning "beautiful," and cheilos (χεῖλος), meaning "lip," a reference to the ornately bearded labellum that is the defining feature of the flowers. The genus was described by Robert Brown in 1810.
Distribution
Beard orchids are found across all Australian states, making Australia the centre of diversity for the genus. A small number of species also occur in New Zealand, New Guinea, and New Caledonia, where one species (Calochilus neocaledonicus) is endemic to maquis shrubland on rocky soils. In temperate Australia and New Zealand, plants favour slopes, ridges, forest, woodland, heath, and wet swamps; in tropical Australia and New Guinea they occur in wet, grassy areas.
Ecology
Calochilus species are seasonally dormant, timing their active growth to available moisture. In tropical regions they complete their life cycle before the onset of the dry season; in temperate areas growth occurs through autumn and winter, with flowering in spring and early summer. Pollination is achieved through sexual deception: male Campsomeris wasps are attracted to the hairy labellum and attempt to mate with it, inadvertently picking up and transferring pollinia. In the absence of a visiting wasp, self-pollination is ensured because the anther sits directly above the stigma and the pollinia drop or crumple onto it.
Taxonomy Notes
The genus was established by Robert Brown in 1810 in Prodromus Florae Novae Hollandiae et Insulae Van Diemen, based on two species: C. campestris and C. paludosus. Brown did not designate a type species at the time of publication. GBIF recognises 23 accepted species while Wikipedia (as of July 2018) lists approximately 30, reflecting ongoing taxonomic revision within the family Orchidaceae.
