Justification
Thelymitra orientalis appears to be endemic to southeastern Australia. There are no formal population estimates for Hoary Sun-orchid. Based on all available count data, there are approximately 11–46 individuals, assuming The Marshes NFR subpopulation consists of 10–45 plants. The main factors that make the species eligible for listing are the small population size, evidence of decline, severe fragmentation and restricted geographic distribution (area of occupancy estimated to be 16 km2). The most serious threats to Hoary Sun-orchid include inappropriate fire regimes, land clearing, vehicle damage, grazing by feral pigs (Sus domesticus), and changes to temperature and precipitation patterns.
Geographic Range Information
The Hoary Sun-orchid appears to be endemic to southeastern Australia. The species appears to occur or have occurred in four subpopulations, KI (Mount Taylor swamp) and The Marshes Native Forest Reserve (NFR) near Nangwarry, South Australia, and Gariwerd (Grampians) National Park (NP) (Syphon Road swamp) and Crib Point in Victoria. However, due to its similar appearance to Plum Sun-orchid and other species in the large Thelymitra pauciflora complex, Hoary Sun-orchid may be more widespread than currently known. Hoary Sun-orchid has also been suggested to occur in a swamp near Rogers Road on the Myponga River at Myponga, South Australia, although plants have not been seen for many years (J. Niejalke pers. comm. 5 March 2022). In addition, no voucher specimen exists of this subpopulation.
Population Information
There are no formal population estimates for Hoary Sun-orchid. Approximately 10–45 plants were known from The Marshes NFR in slashed heath on the edge of a track. A single plant that appears to be of this species has been seen at Crib Point in the last 10 years (G. Backhouse pers. comm. 24 Nov. 2021). Sporadic searches of the Syphon Road swamp site in Gariwerd (Grampians) NP over the last decade have failed to find the species (G. Backhouse pers. comm. 24 Nov. 2021). Its status on Kangaroo Island (KI) is not known, but it has not been recorded since 2008 (ALA 2021).
Habitat and Ecology Information
Habitat
Hoary Sun-orchid occurs in leached white (often peaty) sand, in heathland, damp heathy flats and seepage areas, usually close to sedge-dominated wetlands (Bates 2010). Common co-occurring flora species at The Marshes NFR include Eucalyptus ovata (Swamp Gum) and Acacia melanoxylon (Blackwood), while co-occurring orchids include Thelymitra holmesii (Blue Star Sun-orchid), T. lucida (Glistening Sun-orchid), T. abrupta (Abrupt Sun-orchid), T juncifolia (Rush-leaf Sun-orchid), Cryptostylis subulata (Large Tongue-orchid) and Spiranthes sp. (ladies tresses) (R. Bates pers. comm. 6 Dec. 2021, J. Niejalke pers. comm. 11 Feb. 2022). At Crib Point, Hoary Sun-orchid was recorded in moist sandy loam in heathy woodland with E. viminalis subsp. pryoriana (Coastal Manna-gum) with Themeda triandra (Kangaroo Grass) and Austrostipa spp. (spear grass) (ALA 2021). At Gariwerd (Grampians) NP it occurred with T. holmesii and Microtis atrata (Yellow Onion-orchid) (ALA 2021). At KI the species grew on the edge of a peat bog (R. Bates pers. comm. 23 Nov. 2021).
Reproductive biology
Little is known about the reproductive ecology of Hoary Sun-orchid, and as a result, this section draws largely on published literature from species in the same genus or family.
Flowering occurs from late October to early November, with flowers opening on warm days (Jones 2021). Flowers are reported to be short lived, lasting only a week (J. Niejalke pers. comm. 11 Feb. 2022). As flowering material is required for identification, surveys must be undertaken during this period. The species is facultatively autogamous (can pollinate itself) and may be cleistogamous in cool periods if flowers do not open and self-pollination occurs as the pollinia crumbles and falls onto the stigma (Bates 2010). Although, other blue-flowering Thelymitra species are pollinated by food deception of native bees (Edens-Meier et al. 2014, Jones 2021) and it’s possible that pollination by native bees also occurs in Hoary Sun-orchid. Fruits of Thelymitra spp. take approximately four weeks to mature following pollination. Each mature capsule contains hundreds or thousands of minute seeds that are dispersed by wind when the capsule splits. After fruits have ripened, the plant dies back to its dormant subterranean tubers. Plants reproduce from seed but not clonally, with each tuber annually replaced by a new tuber prior to the old tuber withering. Seed germination requires infection by mycorrhizal fungi from the genus Tulasnella (Warcup 1973).
No data are available regarding the generation length or plant longevity for Hoary Sun-orchid. However, estimates for other terrestrial orchids in southern Australia are typically in the order of several decades (DELWP 2021).
Fire ecology
The fire response of Hoary Sun-orchid is unknown. However, the closely related Plum Sun-orchid displays strong post-fire flowering (TSS 2021). The response of many terrestrial orchids to fire occurring at unnatural times of year (e.g. planned burns) is unknown, but fires during the active growth and flowering stages (April–November) are likely to be deleterious (Jasinge et al. 2018). Fires may also affect pollinator and mycorrhizal fungal communities on which the orchid is dependent (Brown et al. 2016, Jasinge et al. 2018).
Threats Information
The most serious threats to Hoary Sun-orchid include inappropriate fire regimes, land clearing, vehicle damage, grazing by feral pigs (Sus domesticus), and changes to temperature and precipitation patterns.
Use and Trade Information
The cultural, customary and spiritual significance of species and the ecological communities they form are diverse and varied for Indigenous Australians and their stewardship of Country. This section describes some examples of this significance but is not intended to be comprehensive or applicable to, or speak for, Indigenous Australians. Such knowledge may be held by Indigenous Australians who are the custodians of this knowledge and have the rights to decide how this knowledge is shared and used. The cultural significance of Hoary Sun-orchid is not known. The species occurs on land covered by native title agreements with the First Nations of the Southeast People in South Australia and Bunurong People in Victoria (ACHRIS 2021, NNTT 2021). The Indigenous land manager of Gariwerd (Grampians) National Park is the Budja Budja Aboriginal Cooperative and the upper Glenelg River (Siphon Road swamps subpopulation) is part of Djap Wurrung and Jardwardjali land (VSAC pers. comm. 5 July 2022). Kangaroo Island has important cultural significance to the Kaurna, Ngarrindjeri, Narungga and Ramindjeri nations, and these groups maintain a spiritual connection to the region (DEH 2006; Ngarrindjeri Nation 2007). The Kaurna, Ngarrindjeri, Narungga and Ramindjeri peoples would like to be involved in the development and implementation of natural resources management in their traditional lands and waters (Ngarrindjeri Nation 2007). Current members of these nations have a strong understanding of Country and feel responsible for lands and waters (Ngarrindjeri Nation 2007, NRKI 2017). Although little is known of the cultural significance of Hoary Sun-orchid, other orchid species are culturally significant plants for Indigenous Australians, with their tubers used as a food source (Australian National Botanic Gardens 2007). Ascertaining the cultural significance of this species is an information/research priority identified in the Conservation and Recovery Actions.
Conservation Actions Information
Conservation and recovery actions
Primary conservation objective
By 2032, the taxonomy of Hoary Sun-orchid will have been confirmed, and its population will have increased in abundance and viable subpopulations are sustained in habitats where threats are managed effectively.
Conservation and management priorities
Habitat loss, disturbance and modifications impacts- Avoid all further loss and fragmentation of habitat and avoid any negative impacts to known subpopulations.
- Incorporate the Crib Point subpopulation into the conservation reserve system (currently unreserved public land).
- Update the location details of the KI subpopulation and confirm its presence with land managers.
- Update the identification of the Crib Point subpopulation (currently identified as Plum Sun-orchid) and inform land managers of its presence.
- Protect all subpopulations from vehicle damage by physically preventing vehicle access (Crib Point) or installing bollards or signage warning land managers and fire agencies of its presence (KI, The Marshes NFR).
- At the Gariwerd (Grampians) NP subpopulation, if extant, understand the water regime required by the orchid for all stages of its life history, and fulfil these water requirements via an allocation of environmental water from the Glenelg system.
Fire impacts- Ensure that the locations of all subpopulations are recorded on relevant state databases, including those used by land management, forestry and fire response agencies.
- Exclude planned fire from all subpopulations during the growing season (May–October).
- Develop emergency response plans in case of peat fires at The Marshes NFR.
Invasive species (including threats from grazing, trampling, predation)- Develop or maintain feral pig population control measures in consultation with land managers and community groups in and near subpopulations of Hoary Sun-orchid.
- Implement site-based weed control using appropriate methods in consultation with land managers and community groups to ensure that there is no impact on Hoary Sun-orchid.
Climate change and severe weather impacts- Identify and protect any current or future habitat likely to remain or become suitable habitat due to climate change and ensure impacts of other threats to this habitat are minimised.
- Investigate options for maintaining in situ persistence as the climate changes, for example by minimising other population pressures, enhancing resilience and promoting recruitment or supplementing existing subpopulations.
Ex situ conservation- To manage the risk of losing genetic diversity, undertake appropriate seed and mycorrhizal fungi collection and storage, and monitor the viability of stored seed and germination efficacy of fungi. For species where few seed are produced, seed quality is low, or seeds are difficult to store long-term, undertake alternative ex situ storage such as tissue culture and cryopreservation, vegetative propagation or cultivation of living collections. Seed/tissue collection and storage should be conducted in accordance with best practice guidelines and procedures (refer to Commander 2021 or Martyn Yenson et al. 2021).
- If appropriate, and taxonomic issues have been resolved, investigate the feasibility of establishing translocated subpopulations that will improve the conservation outlook of the species. Translocations should be conducted in accordance with best practice guidelines and procedures (refer to Commander et al. 2018), including monitoring translocated subpopulations through to recruitment to ensure they are viable.
Stakeholder engagement/community engagement- Engage and involve Traditional Owners in conservation actions, including surveying for new populations and management actions. Work with Traditional Owners to understand any Traditional Knowledge associated with the species ensuring the practices to record, store and share this knowledge are mutually supported.
- Liaise with relevant land managers to ensure that subpopulations are not accidentally damaged or destroyed. The approval and assistance of land managers should also be sought to implement recovery actions, and most current population data should inform management.
- Engage community groups by encouraging participation in surveys or monitoring for the species.
- Promote public awareness of biodiversity conservation and protection through dissemination of information through print and digital media.
Survey and monitoring priorities- Maintain a monitoring programme to:
- review threats at The Marshes NFR to inform appropriate management actions;
- monitor species recruitment and plant health after fire events;
- determine trends in population size;
- document the post-fire recovery and causes of recruitment failure;
- determine threats and their impacts (particularly the impact of feral goat (Capra hircus) herbivory); and,
- monitor the effectiveness of management actions and the need to adapt them if necessary.
- Undertake surveys to clarify the species’ presence at previously reported subpopulations, and to search for additional subpopulations.
Information and research priorities- Confirm the taxonomic distinctiveness of Hoary Sun-orchid from Plum Sun-orchid and related taxa using genomic approaches supported by morphological studies.
- Re-examine and re-determine herbarium specimens of Hoary Sun-orchid, and Plum Sun-orchid specimens from eastern Australia.
- Increase knowledge surrounding the ecology of Hoary Sun-orchid. This includes improving understanding of habitat requirements, recruitment dynamics, appropriate fire regime, pollination biology (including identity and specificity of pollinators), plant longevity, genetic structure, and minimum viable population size.
- Understand the potential influence of climate change on the long-term survival prospects of the species, due to altered temperatures, rainfall patterns, bushfires, and environmental stressors.
- Investigate the impact of drought on Hoary Sun-orchid recruitment and seedling growth. This is particularly the necessary for the Gariwerd (Grampians) NP subpopulation, which if extant, needs research into the water regime required by the orchid for all stages of its life history.
- Ascertain the cultural significance of Hoary Sun-orchid.
- Determine habitat critical to the survival of Hoary Sun-orchid.
- Undertake vulnerability assessments of the species’ sensitivity and adaptive capacity to changing climatic conditions which draw on genetic, physiological or ecological evidence.
- If vulnerability assessments indicate the species has a high likelihood of extinction due to climate change, undertake research to identify climate refuges that may be suitable for translocations, including both modelling and experimental approaches (e.g. trial translocations). Consideration should be given to the benefits to the species in mitigating climate change related threats, as well as the risks to the recipient site (e.g. introduction of diseases, pests and/or pathogens, and invasiveness of the species).
