Listing Statement for Corunastylis nuda (tiny midge-orchid) Corunastylis nuda tiny midge-orchid T A S M A N I A N T H R E A T E N E D S P E C I E S L I S T I N G S T A T E M E N T Image by Mark Wapstra Scientific name: Corunastylis nuda (Hook.f.) D.L.Jones & M.A.Clem., Orchadian 13(10): 461 (2002) Common name: tiny midge-orchid (Wapstra et al. 2005) Group: vascular plant, monocotyledon, family Orchidaceae Name history: Genoplesium nudum, Prasophyllum beaugleholei Status: Threatened Species Protection Act 1995 : rare Environment Protection and Biodiversity Conservation Act 1999 : Not listed Distribution: Endemic status: Not endemic to Tasmania Tasmanian NRM Region: Cradle Coast, North, South Figure 1. Distribution of Corunastylis nuda in Tasmania, Plate 1. Corunastylis nuda inflorescence showing NRM regions (image by Mark Wapstra) 1 Threatened Species Section – Department of Primary Industries, Parks, Water and Environment Listing Statement for Corunastylis nuda (tiny midge-orchid) IDENTIFICATION AND ECOLOGY grasses and sedges. Even in flower, their short Corunastylis nuda belongs to a group of orchids stature and colour makes them hard to detect in commonly known as midge orchids because of their surrounds. Corunastylis nuda often occurs in their insect-like appearance. Corunastylis species relatively low abundance at any particular site, are deciduous terrestrials with a round, fleshy making detection a chance event. tuber partly enclosed by a persistent fibrous sheath, and a single thin cylindrical leaf. The Description leaf is solid in the basal part, with a short free Corunastylis nuda is a relatively tall midge-orchid, apical part, and is inseparable from the stalk about 18 to 35 cm tall. It has a very slender supporting the inflorescence as they are fused green leaf, which is about 15 to 30 cm long. and emerge from the soil together. The upside- The leaf is closely sheathing and ends well down flowers of Corunastylis species are below the flower spike. The free apical portion crowded in a dense terminal spike. is 10 to 20 mm long. The usually green scape Species of Corunastylis are mostly pollinated by ends in a moderately dense spike of flowers small vinegar flies (drosophilids) attracted to that is 25 to 35 mm long. The flower spike has the flowers by fruit perfumes and hairy between 5 and 40 flowers. The flowers are segments (Jones 2006) but the flowers of nodding and about 4.5 mm long and 3 mm Corunastylis nuda are self-pollinating. wide. The flowers are variable in colour, mainly Reproduction is solely from seed, with fertilised green and red or wholly reddish purple. As they plants elongating considerably prior to seed are self-pollinating, the flowers often do not shedding. Like all orchids this species relies on open widely. The dorsal sepal is 2 mm long and associations with mychorrizal fungi for 1.6 mm wide with hairless margins and a germination and growth. pointed apex. The lateral sepals are deflexed and divergent, 3.5 mm long and 1 mm wide, Midge orchids are most commonly seen in and the apex often has a small gland. The petals places that have been recently burnt or spots are 1.6 mm long and 0.8 mm wide with hairless that are disturbed, regularly mown or slashed, margins and a pointed apex. The labellum is such as areas beside tracks and on road verges. stiffly hinged and ovate, 1.5 mm long and 1 mm It is unlikely that Corunastylis nuda specifically wide. The labellum is thick and fleshy, with requires fire to stimulate flowering, as several margins that are irregularly and finely toothed known forest sites have remained unburnt for or minutely ciliate, and, a pointed apex. relatively long periods,. However, the species is probably favoured by disturbance that [description based on Jones 1998, Jones et al. maintains open patches of bare soil, as 1999, Jones 2006] evidenced by plants growing close to tracks and Confusing species on loose soil associated with road verges and rocky ground. Corunastylis nuda is unlikely to be confused with any other species because of its tiny nodding Survey techniques flowers (often dark reddish), which usually do In Tasmania flowering appears to be mainly in not open widely, and the ovate labellum with January but continues through to February and irregularly toothed or minutely ciliate margins. occasionally March at higher elevations and DISTRIBUTION AND HABITAT colder sites (Wapstra et al. 2008). Mid to late summer is therefore the recommended timing Corunastylis nuda occurs in Victoria, New South for surveys, while noting that Corunastylis nuda Wales, the Australian Capital Territory and can be detected for several months later due to Tasmania (Jones et al. 1999). Within Tasmania its distinctive elongated fertilised plants the species is widely distributed across the (Wapstra et al. 2008). When not flowering, State, excluding the offshore islands (Figure 1). Corunastylis specimens are virtually undetectable Corunastylis nuda occurs in a wide range of as their single thin leaf is often hidden amongst habitats in Tasmania, including scrub, subalpine 2 Threatened Species Section – Department of Primary Industries, Parks, Water and Environment Listing Statement for Corunastylis nuda (tiny midge-orchid) grassland, heathy open forest, open rock plates from sudden processes capable of causing among forest, shrubby dry sclerophyll forest largely irreversible loss of individuals or habitat. and open wet sclerophyll forest, from near sea level to 1000 m elevation on a range of THREATS, LIMITING FACTORS AND different soil types and parent geologies (Jones MANAGEMENT ISSUES et al. 1999). While the highly localised and disjunct distribution of Corunastylis nuda renders patches POPULATION ESTIMATE of the species susceptible to stochastic events Corunastylis nuda is known from at least 26 and accidental destruction, the widespread subpopulations (Table 1). Only a few distribution of the species and some subpopulations have reliable estimates of subpopulations lessens the risk of extinction. abundance and extent. The species appears to Land clearing: The impact on subpopulations occur in low numbers in localised patches of historical clearing of potential habitat is (generally less than 10 individuals) that at times unknown but is unlikely to wholly explain the are spread across several hundreds of metres. disjunct distribution pattern, which is more This makes the area occupied by the species likely a reflection of a widespread species that and the size of the total population difficult to occurs in low abundance. Contemporary estimate. It is unlikely that the total population clearing for activities such as residential numbers in the thousands, though it is likely on developments is having a localised impact on further examination that some subpopulations some subpopulations. will prove to be more extensive and that more Forestry activities: Large areas of potential subpopulations will be discovered with further habitat of Corunastylis nuda have been, and survey. continue to be, commercially harvested. There is strong anecdotal evidence that some forms of RESERVATION STATUS native forest silviculture may be beneficial to Corunastylis nuda is known from Mount Victoria the species, based on the collection of the Forest Reserve, Mount Maurice Forest Reserve, species from selectively harvested forests at Blue Tiers Forest Reserve and Snug Tiers several sites in Tasmania (e.g. Wielangta, Storys Nature Recreation Area. Creek). It is also noted that large areas of known and potential habitat in State forest are Some subpopulations on State Forest have protected in an extensive formal and informal been managed under provisions of the reserve system. Tasmanian Forest Practices Code and are now located in informal reserves under Forestry Inadvertent destruction/disturbance: A Tasmania’s Management Decision number of subpopulations occur on disturbed Classification mapping system (Orr and sites such as edges of tracks. While the presence Gerrand 1998). of the species at such sites is probably a direct result of the initial disturbance event (e.g. CONSERVATION ASSESSMENT establishing the track in the first place), ongoing activities have the potential to eliminate smaller Corunastylis nuda was listed (as Genoplesium subpopulations or parts of subpopulations (e.g. nudum ) in 1995 as rare on schedules of the road widening could destroy tubers through Tasmanian Threatened Species Protection Act 1995 , burial). On the other hand, low intensity at a time when its distribution was poorly maintenance activities (e.g. occasional scraping understood. While the species is now known of a track) may ultimately benefit the species from a number of additional locations, the and assist in maintaining the subpopulation by species typically occurs in low numbers and creating recruitment niches. technically meets criterion B1 for the rare category as the total population consists of fewer than 10,000 mature individuals with no more than 2,500 occurring on land that is free 3 Threatened Species Section – Department of Primary Industries, Parks, Water and Environment Listing Statement for Corunastylis nuda (tiny midge-orchid) Table 1. Population summary for Corunastylis nuda within Tasmania Subpopulation Tenure NRM 1:25000 Years Area Number Region Mapsheet recorded occupied of plants (ha) 1 2.5 km E of Red Marsh, unknown Cradle Coast Mawbanna 2011 0.00001 2 Woolnorth area 2 Sisters Beach nr Rocky unknown Cradle Coast Mawbanna 1970 unknown unknown Cape National Park 3 Track to Ringville State forest Cradle Coast