Rhyolite Midge Orchid - profile

Indicative distribution


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Key:
known
predicted
The areas shown in pink and/purple are the sub-regions where the species or community is known or predicted to occur. They may not occur thoughout the sub-region but may be restricted to certain areas. ( click here to see geographic restrictions). The information presented in this map is only indicative and may contain errors and omissions.
Scientific name: Genoplesium rhyoliticum
Conservation status in NSW: Endangered
Commonwealth status: Endangered
Profile last updated: 17 Aug 2018

Description

Rhyolite Midge Orchid is up to 18 cm tall, with up to twenty 4 mm wide purplish-black flowers. The lateral sepals are swept upwards and the labellum tip is recurved. Flowering occurs for a few weeks in December to January and there is no other summer-flowering orchid in the known range with which it could be confused. Genoplesium is a genus of relatively inconspicuous ground orchids with clustered spikes of dark coloured flowers which are ‘upside down’ relative to most other orchids and have a single flat, not tubular, leaf.

Distribution

The Rhyolite Midge Orchid is endemic to a narrow strip of NSW south coast. Known from only six sites, it is expected that new populations of the Rhyolite Midge Orchid may be found when sites with appropriate habitat are surveyed during the restricted time when the species is in flower. The population numbers at the known sites range from 50 to 1000.

Habitat and ecology

  • All of the documented sites where the Rhyolite Midge Orchid occurs have very shallow soil overlying rhyolite rock.
  • Seasonal drought conditions regularly prevail at these sites and the vegetation is often dominated by lichens and/or moss.
  • Other species which may be present include Tick Bush Kunzea ambigua, Giant Honey-myrtle Melaleuca armillaris, Long-leaved Platysace Platysace lanceolata, Ralston’s Leionema Leionema ralstonii and Tangled Pseudanthus Pseudanthus divaricatissimus. Few herbaceous species are present, however, a number of other orchid species are common associates.
  • The Rhyolite Midge Orchid is a long-lived tuberous geophyte which is only in evidence during the relatively brief period in late spring/early summer when it flowers.
  • Flowering appears to be in response to the current season’s rainfall combined with the amount of nutrient reserves accumulated in the tuber which is in turn related to the conditions during the previous growing season.
  • Plants are likely to take three years before reaching reproductive maturity and, like all orchids, are dependent upon an associated mycorrhizal fungus.
  • Flowering occurs in summer; other Genoplesium species are pollinated by chloropid flies, but the mechanism is unstudied for the Rhyolite Midge Orchid.

Regional distribution and habitat

Click on a region below to view detailed distribution, habitat and vegetation information.


Threats

Recovery strategies

Activities to assist this species

Information sources

IBRA Bioregion IBRA Subregion Known or predicted Geographic restrictions region
South East CornerSouth East Coastal Ranges Known south of Bega River