THREATENED SPECIES SCIENTIFIC COMMITTEE Established under the Environment Protection and Biodiversity Conservation Act 1999

The Minister’s delegate approved this Conservation Advice on 01/04/2016.

Conservation Advice Prasophyllum tunbridgense

Tunbridge leek-orchid

Conservation Status Prasophyllum tunbridgense (Tunbridge leek-orchid) is listed as Endangered under the Environment Protection and Biodiversity Conservation Act 1999 (Cwlth) (EPBC Act). The species is eligible for listing as prior to the commencement of the EPBC Act, it was listed as Endangered under Schedule 1 of the Endangered Species Protection Act 1992 (Cwlth).

The main factors that are the cause of the species being eligible for listing in the Endangered category are its restricted geographic distribution is precarious for its survival due to its restricted extent of occurrence and area of occupancy, and low number of mature individuals.

Prasophyllum tunbridgense (Tunbridge leek-orchid) is listed as Endangered under the Threatened Species Protection Act 1995 (Tasmania).

Description The Tunbridge leek-orchid belongs to a group of orchids commonly known as leek orchids because the erect hollow leaf resembles that of a leek. Prasophyllum species are herbaceous perennial terrestrials with small, fleshy, round or oval tubers and a few fleshy, irregular roots. Most species are dormant over summer and autumn and begin growth in early winter. The single leaf is reddish at the base as opposed to green as in onion orchids (Microtis species). The flower spike emerges through the side of the leaf above the middle, with the portion of leaf above the point of emergence being free and often withered by the time the flowers open. The flower spike bears many flowers that are held upside-down and are often fragrant. The labellum (lower petal) often has prominent wavy or frilly margins (TSS 2010).

The Tunbridge leek-orchid leaf is bright green with a reddish–purplish base, the free part 10–15 being cm long. When in flower the plants are 30–40 cm tall, with 10–25 flowers in a dense spike 6–9 cm long. The ovary is shiny green. Flowers are fragrant, 16–20 mm long and 17–25 mm wide, and are green to light greenish brown, with prominent white petals and a white labellum. The lateral sepals are free, widely divergent and obliquely erect. The petals are 10–12 mm long and 3 mm wide with flared upper margins. The labellum is curved back at right angles below the middle, and the apex is usually curved back through the lateral sepals. The labellum has intensely crinkled margins. The greenish yellow to yellow callus on the labellum has a square to notched apex (Jones 1998; Jones et al. 1999).

The Tunbridge leek-orchid is part of the Prasophyllum patens/truncatum complex. It can be confused with two other members of this complex, Prasophyllum milfordense and Prasophyllum truncatum, but has larger flowers than both these species and the flowers are more crowded. The petals are also longer and wider, with the upper margins flared and are more widely spreading. The labellum is not curved back as sharply as in Prasophyllum truncatum (Jones et al. 1999).

Distribution The Tunbridge leek-orchid is endemic to Tasmania’s Midlands (Jones et al. 1999) and is known from six populations in the Tunbridge – Campbell Town area. The linear range of the species is 30 km, extent of occurrence 66 km2, and area of occupancy less than 2 km2 (Wapstra et al. 2008). The total number of mature individuals recorded in any given year being less than 140 (TSS 2010). Populations occur in Township Lagoon Nature Reserve (Population 1a), on private

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land (Populations 1b, 2, 4 and 5), and on Department of Infrastructure, Energy and Resources (DIER) land (Populations 3 and 6) (TSS 2010).

Plants have not been recorded at three of the smaller sites (Populations 3, 5 and 6) for some years despite targeted surveys, while there has been a marked decline in numbers at the larger populations (Populations 1a and 4), presumably from drought. The lack of plants at the Township Lagoon site in 2009 (four plants compared to 40 plants in 1999) is at odds with the response of the allied species Prasophyllum incorrectum and Prasophyllum olidum at Campbell Town golf course, both showing a significant increase in numbers following above-average autumn and winter rains (Schahinger 2009).

The scarcity of records for Tunbridge leek-orchid is not likely to be a result of a spasmodic flowering pattern in response to disturbance such as fire, as it is known to flower freely in the absence of fire and extensive searches have been undertaken of potential habitat since 1999. The likelihood of additional sites being uncovered is low (TSS 2010).

Relevant Biology/Ecology The Tunbridge leek-orchid occurs in one of the driest regions of Tasmania with an annual rainfall of about 500 mm, at an altitude of 200–240 m above sea level. The species grows in native grassland on well-drained loams derived from basalt (TSS 2010).

The species flowers during October to early November. The labellum produces quantities of nectar on which a wide range of insects feed. Some of these insects, particularly native bees, wasps and beetles, are effective pollinators (TSS 2010).

Associated species include Themeda triandra, Austrodanthonia spp., Austrostipa spp., and a range of herbs, lilies, mosses and lichens. Threatened flora species associated with the Tunbridge leek-orchid include the EPBC-listed Dianella amoena, Glycine latrobeana, Leucochrysum albicans and Pterostylis commutata, and the State listed Pultenaea prostrata, Stackhousia subterranea, Velleia paradoxa and Vittadinia cuneata (TSS 2010).

Threats Table 1 – Threats

Threat factor Threat Threat Evidence base type status Habitat loss, disturbance and modifications Land known past Large scale conversion of native grasslands to clearance pasture in the Midlands would have reduced the habitat of Tunbridge leek-orchid in the past and has most likely resulted in the restricted distribution it has today. In particular, topdressing with superphosphate in the 1950s could have caused local extinctions, rendering potential grassland habitat uninhabitable for this species and other orchids (TSS 2010). Stochastic potential future The Tunbridge leek-orchid extant at two of its six risk sites, with an apparent decline in numbers at the two extant sites to just a few plants. The very low plant numbers and small area of occupancy expose the species to a high risk of extinction through chance events (TSS 2010). Impacts of domestic species Grazing known current Grazing by stock during the species’ flowering and fruiting period poses a threat to those populations Prasophyllum tunbridgense (Tunbridge leek-orchid) Conservation Advice Page 2 of 4

on private land. All flowering plants in Population 2 are known to have been grazed by sheep in early November 1999 — plants were last seen there in 2001 (TSS 2010).

Conservation Actions

Conservation and Management priorities Habitat loss, disturbance and modifications

o Prevent habitat disturbance. Control access routes by installing gates to suitably constrain stock and vehicle access to known sites on public land and manage access on private land, to protect known populations and habitat from damage.

o Ensure land managers are aware of the species’ occurrence and provide protection measures against key and potential threats. Impacts of domestic species

o If livestock grazing occurs in the area, ensure land owners/managers use an appropriate management regime, avoid any trampling on or near the orchid and at a stocking density that does not detrimentally affect this species to allow regeneration from seedlings and manage total grazing pressure at important sites through exclusion fencing or other barriers. Stakeholder Engagement

o Provide information and extension support to relevant Natural Resource Management committees, local councils, Government agencies and the local community on the location, significance and management of known populations and areas of potential habitat.

o Continue to liaise with landowners/managers (Campbell Town golf course, private landowners, DIER) of sites where conservation covenants are in place, and ensure the associated management plans are being adhered to.

o Prepare a management strategy with input from local experts.

Survey and Monitoring priorities • Continue to monitor known populations annually to determine the level of recruitment and/or plant loss to better inform management prescriptions. • Continue to monitor covenant compliance and review management prescriptions to maintain suitable habitat for the species. • Continue to undertake extension surveys of native grasslands in Tasmania’s Midlands to locate any additional populations/occurrences/remnants. • Collect seed and mycorrhiza for long-term storage at the Tasmanian Seedbank Conservation Centre (Royal Tasmanian Botanical Gardens). • Monitor the progress of recovery, including the effectiveness of management actions and the need to adapt them if necessary.

Information and research priorities • Investigate options for linking, enhancing or establishing additional populations.

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• Fire trials should only be undertaken as a last resort when all other means of regeneration of the species has been investigated and, in addition, all weed management and fire impacts including the timing of fire impacts are fully understood. • Undertake seed germination and/or vegetative propagation trials to determine the requirements for successful translocation. • Implement an annual census to monitor emergence and resprouting success.

References cited in the advice

Jones, D.L. (1998). Contributions to Tasmanian Orchidology – 6: A taxonomic review of Prasophyllum R. Br. in Tasmania. Australian Orchid Research 3: 94–134.

Jones, D. Wapstra, H., Tonelli, P., & Harris, S. (1999). The orchids of Tasmania. Melbourne University Press.

Schahinger, R. (2009). Prasophyllum incorrectum & Prasophyllum olidum at Campbell Town Golf Course: November 2009 monitoring report. Unpublished report, Department of Primary Industries, Parks, Water and Environment, Hobart.

Wapstra, M., Roberts, N., Wapstra, H. & Wapstra, A. (2008). Flowering times of Tasmanian orchids: a practical guide for field botanists. Self-published by the authors.

Other sources cited in the advice

TSS (Threatened Species Section) (2010). Listing statement for Prasophyllum tunbridgense (Tunbridge leek-orchid), Department of Primary Industries, Parks, Water and Environment, Tasmania. Viewed: 11 December 2015. Available on the internet at: http://dpipwe.tas.gov.au/Documents/Prasophyllum- tunbridgense-listing-statement.pdf

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