Listing Statement for benthamiana (blotched sun-orchid)

Thelymitra benthamiana

blotched sun-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 Hans and Annie Wapstra

Scientific name: Rchb.f., Beitr. Syst. Pflanzenk. 55 (1871) Common name: blotched sun-orchid (Wapstra et al. 2005) Group: vascular , , family

Status: Threatened Protection Act 1995 : endangered Environment Protection and Biodiversity Conservation Act 1999 : Not listed

Distribution: Endemic status: Not endemic to Tasmanian NRM Region: North

Figure 1. The distribution of Thelymitra benthamiana Plate 1. Thelymitra benthamiana within Tasmania (image by Hans and Annie Wapstra)

1 Threatened Species Section - Department of Primary Industries, Parks, Water and Environment

Listing Statement for Thelymitra benthamiana (blotched sun-orchid)

IDENTIFICATION AND ECOLOGY green, leathery and obliquely upright. It has the Species of Thelymitra are commonly called sun- most distinctive leaf of any Thelymitra species in orchids because the flowers of most species Tasmania. The flower stems are 20 to 40 cm open only in warm to hot weather, particularly tall and are green with several small bracts. The on bright, sunny days. Thelymitra species are inflorescence comprises 2 to 10 flowers, which terrestrial orchids that die back after flowering are 30 to 40 mm across, greenish yellow with to fleshy subterranean tubers. They are all numerous reddish brown to dark brown spring or summer flowering. Most species have blotches and suffusions and externally dull a single narrow basal leaf although that of greenish brown. The flowers open freely in Thelymitra benthamiana is unique among warm weather and are long lasting. The Tasmanian species in being ovate and leathery and are 15 to 20 mm long and 6 to 10 making the species identifiable to species level mm wide, the labellum being the narrowest of even in the vegetative state. Unlike most the flower segments. The is yellow, orchids, the labellum (lip) of the Thelymitra spotted or blotched, very broadly winged, with flower is generally similar in shape and size to the wings spreading like a mantle and also the petals. Features of the column in the centre yellow, spotted and deeply fringed. The post- of the flower are important in the identification anther lobe is narrow, thick and bulbous. of most species. In all species the column has two arm-like projections that flank the anther [description from Jones 2006] (pollen holding structure). Confusing species Flowers of Thelymitra , which often open widely Thelymitra benthamiana is unlikely to be confused in warm weather, are thought to mimic native with any other Tasmanian species because of its irises and lilies, thus attracting a similar suite of large, bright green, leathery leaf and highly pollinating insects, such as small native bees, distinctive blotched yellow-brown flowers (it is that attempt to collect pollen and often bring one of only three yellow-flowered species and about pollination (Jones et al. 1999). Thelymitra easily distinguished from the other species due benthamiana has long-lasting flowers that open to its blotchy brown flowers). freely and can be both insect-pollinated and self-pollinating (Jones 2006). The flowering of many sun-orchids is enhanced by disturbance, DISTRIBUTION AND HABITAT and as a result some species may be prominent Thelymitra benthamiana occurs in southern in disturbed sites such as slashed areas, or along Victoria, South , and track verges and road embankments. Thelymitra in northeastern Tasmania. Within Tasmania it is mucida is one such species, responding only known from three locations on Flinders positively to summer fires and the species can Island (Table 1, Figure 1), separated by about 4 be found in disturbed areas. km and occupying less than 2 hectares.

The flowering period of Thelymitra benthamiana On the mainland, Thelymitra benthamiana is on mainland Australia is September to widespread and common, growing in open December (Jones 2006). In Tasmania, flowering forest, heathy forest and heathland in well- commences in late October so late October to drained sandy soil and clay loam (Jones 2006). late December is the likely flowering period in In Western Australia, the species is often found this State and the recommended timing for in association with winter-wet soil and on surveys (Wapstra et al. 2008). Note that margins of granite outcrops (Jones 2006). On identification prior to this period is possible Flinders Island, Thelymitra benthamiana occurs on from leaves due to their distinctiveness. slopes and hill tops associated with areas of heathy eucalypt woodland, open Description heathy/scrubby vegetation, bare ground and exposed rock that is sedimentary in origin and Thelymitra benthamiana has a leaf that is ovate, 5 unique to this part of Flinders Island. to 15 cm long and 2 to 3.5 cm wide, bright

2 Threatened Species Section - Department of Primary Industries, Parks, Water and Environment

Listing Statement for Thelymitra benthamiana (blotched sun-orchid)

Table 1. Population summary for Thelymitra benthamiana within Tasmania

Subpopulation Tenure NRM 1:25000 Year last Area Number Region * Mapsheet seen occupied of mature (ha) 1 Centre Hill, Flinders Island Private North Memana 2005 0.5-1 c. 130 property 2 Melrose Road, Flinders Island Private North Memana 2001 0.1? < 20 property 3 north of Mulligans Hill, Private North Memana 2005 0.005 c. 10-20 Flinders Island property *NRM region = Natural Resource Management region

POPULATION ESTIMATE THREATS, LIMITING FACTORS AND MANAGEMENT ISSUES Thelymitra benthamiana is represented by three subpopulations, totalling fewer than 200 Stochastic risk: Low numbers and the highly individuals. The first subpopulation discovered localised distribution of Thelymitra benthamiana on Centre Hill in 1999 supported about 130 on unreserved private land makes the species individuals (spread over 130 by 60 m). The susceptible to chance events. This is second subpopulation discovered in 2000 about exacerbated by the relationship with 3 km to the west of Centre Hill supported mychorrizal fungi which may make the species fewer than 20 plants (precise extent not susceptible to additional factors The precise documented but indicated as being a small area extent of each of the subpopulations is also not only). These two subpopulations are separated formally documented so disturbance from by unsuitable habitat (i.e. pasture). The third nearby activities has the potential to impact the subpopulation occurs about 1 km further west sites supporting the species. on a ridge north of Mulligans Hill and was also Land clearing: Any clearing activities discovered in 2000. It seems unlikely that conducted near Thelymitra benthamiana are likely significant range extensions will be made to deleteriously affect the species through because the habitat (especially the geology) with changes to vegetation and soil structure, and which Thelymitra benthamiana is associated is associated impacts of altered grazing/browsing relatively restricted and much of Flinders Island regimes. Any clearing of vegetation on similar has been well surveyed for orchids by local geology on Flinders Island may result in the specialists and the species is distinctive. Even if further loss of potential habitat for the species. new subpopulations are discovered, the Inappropriate grazing and disturbance conservation status of the species would likely regime: The known subpopulations are subject remain unchanged. to grazing and stock trampling and there are signs of erosion caused by stock trampling, RESERVATION STATUS which could lead to changes in population Thelymitra benthamiana occurs on unreserved structure. A change from sheep to cattle grazing private property. is likely to increase impacts to the habitat e.g. from the introduction of weeds. Changes to CONSERVATION ASSESSMENT fertilising practices are also a threat (e.g. even a one-off fertiliser application is likely to Thelymitra benthamiana was listed in 2005 as eliminate the species). Part of the area endangered on schedules of the Tasmanian supporting Thelymitra benthamiana on Centre Hill Threatened Species Protection Act 1995 , meeting has been disturbed by heavy machinery, and the criterion B because there are fewer than 250 site north of Mulligans Hill occurs on disturbed mature individuals and its range is severely heathland that has been scraped by machinery. restricted (it occupies less than 2 hectares, and Inappropriate fire regime: The flowering of it occurs in only 3 nearby subpopulations). Thelymitra benthamiana is likely to be enhanced

3 Threatened Species Section - Department of Primary Industries, Parks, Water and Environment

Listing Statement for Thelymitra benthamiana (blotched sun-orchid) by summer fires. For safety reasons, fire • implement a fire management regime management at the known sites and in potential suitable for dry heathy scrub and woodland habitat for Thelymitra benthamiana is usually should the vegetation become too dense for directed towards preventing the type of fires the species, especially in the absence of considered ideal to stimulate flowering. A more stock grazing; frequent lower intensity fuel reduction fire • regime is unlikely to benefit the species and in monitor known sites and nearby similar habitat during the flowering season to the long term may reduce habitat quality. Fire may be required to maintain open habitat for determine condition of the habitat (including openness of the vegetation and the species in the absence of stock grazing. emerging threats) and population trend Climate change: While Thelymitra benthamiana including response to altered grazing occurs in a region with naturally low rainfall, regimes, fire and climatic conditions; climatic warming has the potential to further exacerbate the precarious position of the • undertake extension surveys of potential species, particularly if the rainfall pattern habitat in nearby areas during the flowering changes. This may be further complicated by period of the species. changed grazing pressures linked to changes in • provide information and extension support climatic conditions. to relevant Natural Resource Management committees, local councils, Government MANAGEMENT STRATEGY agencies and the local community on the location, significance and management of What has been done? known subpopulations and areas of Thelymitra benthamiana was formally included in potential habitat; the Flora Recovery Plan: Threatened Tasmanian • implement the threatened orchid recovery Orchids 2006–2010 (TSU 2006). plan (TSU 2006) and include the species in any revision of the plan. Management objectives BIBLIOGRAPHY The main objective for the management of Thelymitra benthamiana is to ensure that there is Jones, D. (2006). A Complete Guide to Native no decline in the known subpopulations . Orchids of Australia including the Island Territories . New Holland Publishers (Australia), Sydney. What is needed? TSU (Threatened Species Unit) (2006). Flora • determine the precise extent and condition Recovery Plan: Threatened Tasmanian Orchids of known subpopulations, and develop 2006–2010 . Department of Primary appropriate management strategies for each Industries and Water, Hobart. of the sites; Wapstra, M., Roberts, N., Wapstra, H. & • pursue a more formal land management Wapstra, A. (2008). Flowering Times of agreement with the owners of the Tasmanian Orchids: A Practical Guide for Field properties supporting Thelymitra benthamiana Botanists . Self-published by the authors (April that incorporates longer term habitat 2008 version). maintenance objectives and actions Wapstra, H., Wapstra, A., Wapstra, M. & including fencing, grazing control, weed Gilfedder, L. (2005). The Little Book of management and prescribed burning; Common Names for Tasmanian Plants . • reduce or exclude stock grazing pressure to Department of Primary Industries, Water reduce the risk of overgrazing, trampling, and Environment, Hobart. weed introduction and inadvertent damage;

4 Threatened Species Section - Department of Primary Industries, Parks, Water and Environment

Listing Statement for Thelymitra benthamiana (blotched sun-orchid)

Prepared in October 2008 under the provisions of the Tasmanian Threatened Species Protection Act 1995. Approved by the Secretary and published in July 2010. Cite as: Threatened Species Section (2010). Listing Statement for Thelymitra benthamiana (blotched sun-orchid) , Department of Primary Industries, Parks, Water and Environment,

Tasmania.

View: www.dpipwe.tas.gov.au/threatenedspecieslists Contact details: Threatened Species Section, Department of Primary Industries, Parks, Water and Environment, GPO Box 44, Hobart, Tasmania, Australia, 7001. Ph (03) 6233 6556; fax (03) 6233 3477. Permit: It is an offence to collect, disturb, damage or destroy this species unless under permit.

5 Threatened Species Section - Department of Primary Industries, Parks, Water and Environment