Prasophyllum Robustum

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 robustum robust leek-orchid Conservation Status Prasophyllum robustum (robust leek-orchid) is listed as Critically Endangered under the Environment Protection and Biodiversity Conservation Act 1999 (Cwlth) (EPBC Act). The main factors that are the cause of the species being eligible for listing in the Critically Endangered category are its very restricted geographic distribution, extent of occurrence and area of occupancy, and its very low number of mature individuals (TSSC 2001). Prasophyllum robustum (robust leek-orchid) is listed as Endangered under the Threatened Species Protection Act 1995 (Tasmania). Description The robust leek orchid belongs to a group of orchids commonly known as leek orchids because the erect hollow leaf has some resemblance to 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 often has prominent wavy or frilly margins (TSU 2000). The leaf of the robust leek orchid is dark green with a red to purple base, the free part 10–20 cm long. When in flower, the plants are 40–110 cm tall, with 15–30 flowers in a loose spike 15–25 cm long. The ovary is shiny green. The flowers are 15–20 mm long and 15–20 mm wide and have greenish brown to brownish sepals with 3–5 dark brown markings prominent on the lowermost sepal, whitish petals with a brown median band and a white labellum. The lateral sepals are not united and are very widely divergent. The petals are 10–11 mm long and 2.5 mm wide and are widely spreading. The labellum is sharply curved back on itself near the middle, the apex curved back through the lateral sepals. It has irregularly crinkled margins. The fleshy green callus on the labellum has a shallowly notched apex and extends to the bend on the labellum (TSU 2000). The robust leek-orchid is part of the Prasophyllum patens/truncatum complex. It can be confused with another member of this complex, Prasophyllum stellatum, but can be distinguished from this species by its wider petals, labellum apex that curves back through the lateral sepals and callus that only extends to the bend in the labellum. It can also be distinguished from Prasophyllum stellatum by its lowland distribution and earlier flowering time. Prasophyllum robustum was previously known as Prasophyllum patens var. robustum and had not been collected since the early 1900s. It was presumed extinct until rediscovered at Latrobe in 1995 (TSU 2000). Distribution The robust leek-orchid is endemic to Tasmania and is known from one location on private land at Dooleys Hill, Latrobe. In 1998 the single population contained an estimated 50 mature individuals. Another population last seen at Smithton in 1940 is extinct. Although the species may be stimulated by fire, it does not entirely depend on fire to produce flowers, giving confidence to the population estimate. There is little potential habitat remaining following Prasophyllum robustum (robust leek-orchid) Conservation Advice Page 1 of 4 extensive clearing in the past of forest on basalt for agriculture, and it is unlikely that many, if any, new populations remain to be found (TSU 2000). Relevant Biology/Ecology The robust leek-orchid occurs in grassy and shrubby Eucalyptus amygdalina forest on well- drained brown loam derived from basalt (TSU 2000). It flowers in November and December. The labellum produces quantities of nectar on which a wide range of insects feed. Some of these, particularly native bees, wasps and beetles, are effective pollinators (TSU 2000). Threats Table 1 – Threats Threat factor Threat Threat Evidence base type status Habitat loss, disturbance and modifications Habitat loss potential future In 2000, the owners of the Dooleys Hill block of land were aware of the significance of the needs of the orchid in particular, and have been successfully managing the land for some years. In 2000, the block was being investigated for a possible covenant under the Regional Forest Agreement as little of this habitat remains following extensive clearing in the past for agricultural activities. Until some formal arrangement is agreed upon, the threat of the population being cleared continues to apply (TSU 2000). Fire Fire potential future Infrequent fire is a potential threat to the robust frequency leek-orchid. Management has included patch burning which has served to keep the habitat open and may have stimulated flowering (TSU 2000). Impacts of domestic species Grazing by potential future The area surrounding the private block of land horses has been largely cleared and converted to housing or pasture for horses. Although management of the land may include some grazing to ensure the habitat remains open, grazing could still pose a threat in the future (TSU 2000). Conservation Actions Conservation and Management priorities Habitat loss disturbance and modifications o Pursue management options with landowners/managers to protect the population of the robust leek-orchid against possible changes in land use that would be detrimental to the species. Management may include some grazing (e.g. horses) and fire to ensure the habitat remains open. o Do not alter current management if the population is thriving. Prasophyllum robustum (robust leek-orchid) Conservation Advice Page 2 of 4 Fire o Implement and/or maintain an appropriate fire management regime for protecting key habitat includes ensuring buffers to prevent wildfire or managed fire from impacting the habitat unless prescribed fire is being used following sound scientific evidence of the critical need for such a prescribed fire. o Critically, any use of prescribed or experimental fires must be very well justified, and should be typically an action of last resort. There must be a carefully planned weed management strategy post-fire, and demonstrated funding to ensure post-fire monitoring and control actions occur (e.g. weed control based on sound scientific evidence). o Provide maps of known occurrences to local and state Rural Fire Services and seek inclusion of mitigation measures in bush fire risk management plan/s, risk register and/or operation maps. Impacts of domestic species o If livestock grazing (e.g. by horses) occurs in the area, ensure land owners/managers use an appropriate management regime and 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 Establish a mechanism to ensure management intervention when required. o Prepare and implement a management strategy with input from local experts. o Continue to liaise with private landowner to consider and maintain long-term protection e.g. private nature reserve, management agreement, covenant, etc. Survey and Monitoring priorities • Undertake survey work in November and December (when the plants are flowering), in suitable habitat and potential habitat to locate any additional populations/occurrences/remnants. • Monitor the known populations, particularly at flowering time, for threats and declines. • 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 enhancing or establishing additional populations. • 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. Prasophyllum robustum (robust leek-orchid) Conservation Advice Page 3 of 4 Sources cited in the advice TSSC Lisitng Advice (Threatened Species Scientific Committee) (2001). Prasophyllum robustum (robust leek-orchid). Viewed: 31 March 2016. Available on the Internet at: http://www.environment.gov.au/node/16469 TSU (Threatened Species Unit) (2000). Listing statement robust leek-orchid Prasophyllum robustum. Department of Primary Industries, Water and Environment, Tasmania. Viewed: 14 December 2015. Available on the internet at: http://dpipwe.tas.gov.au/Documents/Prasophyllum-robustum-listing- statement.pdf Prasophyllum robustum (robust leek-orchid) Conservation Advice Page 4 of 4 .

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