Cyrtostylis, commonly known as gnat orchids, is a small genus of five or six species of terrestrial orchids in the family Orchidaceae (order Asparagales). The genus was first formally described in 1810 by the Scottish botanist Robert Brown in his landmark work Prodromus Florae Novae Hollandiae, with Cyrtostylis reniformis designated as the type species.
Plants in this genus are perennial, deciduous, and sympodial herbs. Each plant typically produces a single heart-shaped, ground-hugging leaf and a slender flowering stem bearing one to a few pale, insect-like flowers. The lateral sepals and narrow lance-shaped petals are roughly equal in length; the labellum is oblong and stalkless, projecting outward, with two conspicuous bead-like glands and two longitudinal ridges along its surface. The column is curved and about half as long as the labellum — a distinctive feature that gives the genus its name. Cyrtostylis orchids frequently form dense colonies of genetically identical plants through vegetative reproduction.
The genus is native to Australia and New Zealand. Australian species — including the widespread C. reniformis (common gnat orchid) and C. robusta (large gnat orchid) — occur across all six states. Two species, C. oblonga and C. rotundifolia, are endemic to New Zealand, where they grow in coastal to lower montane habitats such as open clay pans, lightly shaded scrub, and shallow leaf litter.
Cyrtostylis resembles the related genus Acianthus, but can be distinguished by the absence of long appendages on the tips of the sepals and petals, and by differences in the lateral sepals. Recent molecular phylogenetic work suggests the genus is not closely allied to Acianthus but is instead sister to Corybas (in a broad sense including several segregate genera).
Etymology
The name Cyrtostylis is derived from the Greek kyrtos ("curved") and stylos ("pertaining to the style"), referring to the distinctively curved column present in all species of the genus.
Distribution
Cyrtostylis is native to Australia and New Zealand. In Australia, species such as C. reniformis are distributed across all six states. In New Zealand, two endemic species — C. oblonga and C. rotundifolia — are restricted to the northern North Island and the Manawatāwhi / Three Kings Islands, where they grow in coastal to lower montane habitats.
Ecology
Gnat orchids are terrestrial herbs of open or lightly shaded habitats, including clay pans, scrub margins, basalt rock outcrops, and shallow leaf litter, from coastal to lower montane elevations. They flower in winter to spring (July–November in New Zealand). Plants often form dense clonal colonies through vegetative spread. In Australia, species occur in a range of open woodland and forest-edge situations across all six states.
Taxonomy Notes
The genus was formally established by Robert Brown in 1810, with C. reniformis as type species. Species counts differ by authority: the World Checklist of Selected Plant Families recognizes five species, while Australian authorities recognize six, the discrepancy arising from the treatment of C. huegelii (considered a synonym of C. reniformis var. huegelii by the Checklist). Some authors have proposed treating Cyrtostylis as a synonym of Acianthus, but molecular phylogenetic studies indicate the two genera are not closely related; instead, Cyrtostylis appears to be sister to Corybas (broadly circumscribed to include Anzybas, Nematoceras, Singularybas, and Molloybas).
