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Metallic Sun-orchind - Thelymitra epipactoides |
Metallic Sun-orchid Thelymitra epipactoides | |||||||||||||
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The Metallic Sun-orchid (Thelymitra epipactoides) is one of the largest and most impressive of the Thelymitra. It grows from a subterranean tuberous root and when fully developed has a single, erect, sheathing leaf to 25cm and a flower stem to 50cm tall which contains 5-20 flowers. Flower colour is highly variable, brown, copper, blue and green being the main colour groups which are determined by the proportion of red, blue and green epidermal cells, some of which are reflective giving a metallic appearance.
Metallic Sun-orchid. Flower colour is highly variable. Image: Noushka Reiter |
A sweet scent is produced when flowers open, usually in Sptember - October and only on warm sunny days with low humidity. Mature non-flowering plants produce a single, erect, linear-lanceolate leaf to 51cm tall. Immature plants produce a linear leaf to about 30cm, usually on an acute angle to the ground (Cropper et al 1989, Cropper & Calder 1989, Backhouse & Jeanes 1995).
Historic distribution of Metallic Sun-orchid in Victoria. Source: DEPI Victorian Biodiversity Atlas, accessed 29 August 2014. |
The Metallic Sun-orchid is distributed in southern Victoria and southeastern South Australia. It was once widespread along coastal areas of Victoria from Gippsland to the far Southwest and extending inland to the Wimmera. Remaining populations are now isolated and mainly confined to parks and reserves. Apart from a few populations in the coastal areas of Gippsland such as the Gippsland Lakes Coastal Park, Blond Bay Wildlife Reserve and at Golden Beach the south-west region of Victoria contains the majority of remaining sites. Significant areas are Port Campbell National Park, Bay of Islands Coastal Park, the Tooloy-Lake Mundi Wildlife Reserve, the Kiata Flora & Fauna Reserve and sections of the Grampians National Park in the Wimmera. In Gippsland, Blond Bay Wildlife Reserve and Gippsland Lake Coastal Park are important areas for this species.
Many sites are no longer viable or in a state of decline e.g. No sightings have been seen in Mocamboro Flora Reserve or the Lower Glenelg National Park for the last five years (Pitts pers. comm.) despite extensive surveying with the Australian Native Orchid Society between 2009-2011. The plants in Port Campbell are thought to be in decline as a result of increased biomass due to inappropriate fire regimes, invasion of coast wattle and increased browsing.
Population estimates vary from about 1050 plants in Australia (DEH 2006), to less than 3,000 plants (Coats et al 2002). More recent assessments suggest the population could be less than 1500 plants in the wild which comprise seven main populations in Victoria.
Habitat & ecology
Typical habitat utilising bare area under dead vegetation |
Metallic Sun-orchid non flowering mature form |
Key habitat characteristics are sub-humid environments where there may be a period of water stress in the summer and cool to wet winters in which soils comprising sandy loams overlying a clay subsoil have a tendency to become waterlogged.
The Metallic Sun-orchid also favours stable mature open heathland vegetation communities close to the coast where there is a mosaic of disturbed sites. These areas are often dominated by;
Immature plants have been observed growing around old Leptospermum stumps.
The inland site near Casterton is dominated by; Prickly Tea-tree Leptospermum juniperinum in association with sedgelands which provide more favourable habitat. At Kiata, open shrubland is dominated by Wattles Acacia sp. with a shrubby ground cover of Flame Heath Astroloma conostephioides. The Metallic Sun-orchid is also found in association with a mycorrhizal fungi Tulasnella asymmetrica that may assimilate nutrients for the orchid (Cropper et al 1989, Calder et al 1989).
The Metallic-sun orchid has a dormant period between January to March, during this period the leaf and flower stem wither, this may assist the orchid in coping with events such as water stress during dry conditions and also avoid the likelihood of being damaged by fire. Generally by April a single leaf emerges, the flower stem develops in August and is fully mature during October, ( flowering can occur from September to November depending on the season and site conditions). By December the seeds are fully developed.
The Metallic Sun-orchid regenerates almost exclusively from seed that falls on sites where soil or plant community disturbance has occurred. Typical examples are; opening of canopy through death of structurally dominant plants, salt induced dieback, digging by fauna such as echidnas, regular but infrequent fires, browsing and trampling by Kangaroos and Wallabies. Also minor land management activities such as track works may assist in opening up small areas, however this also comes with an added risk of introducing the spread of invasive weeds.
The flower colour and scent attract insects which provide pollination, although there is no obvious reward for pollinators as no nectar is produced. Native bees, genus Nomia are known to pollinate the Metallic Sun-orchid, in effect they are deceived by the flower’s colour and scent. The variety of flower colours within this species may also act as a means of ensuring pollinators remain attracted to the flower despite there being no nectar (Cropper & Calder 1989).
The spread of Acacia longifolia into coastal heathlands has been identified as an issue. Any form of weed invasion that smothers out light or prevents the opportunity for seed to germinate on small areas of bare ground is of concern. Weed invasion often results from disturbance to soil and vegetation, particularly where there is already a weed source in the vicinity and there is mechanical disturbance such as grading, digging etc. Weeds are often spread along walking tracks and vehicle tracks and have the potential to invade suitable orchid habitat.
Common causes are construction or changes to road or tracks or drainage of areas which can impact on the surface or sub-surface movement of water and alter the natural cycle of seasonal waterlogging and drying out of sandy loams, this being one of the habitat requirements necessary to support the Metallic Sun-orchid.
Reduced seed production and impaired seed germination can be caused by changed ecological conditions, e.g. lack of occasional fires. Long term changes to the floristic composition of habitat can result in the loss of heathlands due to the expansion of structurally dominant species. This can alter the natural mosaic of small disturbed areas suitable for seedling development. A lack of occasional fires can also retard the floristic diversity of an area and reduce pollinators that are necessary for successful seed development. Hand pollination has been carried out with some success to overcome a lack of natural pollinators.
Grazing by stock or native herbivores such as the Kangaroo and Wallaby can cause sever browsing damage. At some locations this has been identified as a major problem as it can severely impact on the production of seed for future recruitment of the orchid. Deer and the European Rabbit are also recognised as a problem in browsing flower stems. There are cases where the entire flowering crop of a local population has been wiped out due to rabbits (Cropper et al 1989).
Chrysomelid Beetle lavae and Tortricid Moth lavae have been observed to graze on leaf material leading to the loss of leaf (Cropper et al 1989).
Physical damage includes trampling of plants and digging out plants. Trampling can be a major problem at high visitor areas as the delicate flower stems are easily damaged. Digging out plants is illegal as this species protected under under the Flora & Fauna Guarantee Act 1988, it results in the loss of plants which can impact on recruitment potential. It also assists the spread of invasive weeds into areas which can limit the viability of local populations.
Key actions necessary to maintain the viability of this species, identified by Calder et al 1989.
These actions are undertaken by DEPI and partners such as Parks Victoria, Australian Native Orchid Society, Australian Orchid Foundation, RMIT University, University of Melbourne, Royal Botanic Gardens, CMA's, Horsham Orchid Propagation Facility, Community groups including: the Portland Field Naturalist, the Bairnsdale and Districts Field Naturalists and the Grampians Threatened Species Group and individual naturalists have all been actively involved in the recovery program for this species.
Grampians National Park
Kiata Flora and Fauna Reserve
Tooloy-Lake Mundi Wildlife Reserve
Lower Glenelg National Park
Mocamboro Flora Reserve
Wilkin Flora & Fauna Reserve
Bay of Islands Coastal Park
Port Campbell National Park
Blond Bay Wildlife Reserve
Dutson Downs Pipeline Block - Gippsland Water
Gippsland Lakes Coastal Park
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Metallic Sun-orchids in the laboratory 6 months old. | |
Metallic Sun-orchids in the laboratory 12 months old. |
In 2010 a draft re-introduction plan was developed for Thelymitra epipactoides and circulated amongst the Recovery Team for comment. This plan sets out the most important activities to be undertaken to ensure recovery of this species.
A monitoring system of recording demographic information such as leaf emergence, flowering, pollination, grazing and recruitment has been established across three Metallic Sun-orchid sites in western Victoria Lake Mundi, Kiata, Flaxman’s Hill and Port Campbell. Ongoing comparative data from these three sites will be used to further define management actions and priorities for this species.
In 2010 a collaborative research project was initiated as part of an Australian Orchid Foundation project with RMIT University, University of Melbourne, Royal Botanic Gardens and DSE. The project will run for three years and will investigate the edaphic conditions experienced by Metallic Sun-orchids, the identity and diversity of mycorrhizal populations associated with these populations, whether mycorrhizal fungi form tripartite links with associated flora, and the optimal in-vitro germination and nursery growth conditions to raise these plants.
A collection of approximately 3,000 propagated plants is being maintained at the Horsham Orchid Propagation Facility genetic material sourced from Lake Mundi, Kiata and Port Campbell. These are now ready for introduction into the wild, commencing in the Wimmera July 2012.
International Student Volunteers and DSE Land and Fire Indigenous trainees completed weed and rabbit management works in preparation for a re-introduction in July 2011.
At Kiata, all 15 plants in which flowered were individually cross pollinated and parentage setting seed recorded. Seed from these plants were harvested for propagation and the site was re-stocked with seed in autumn. Ten root samples were harvested from plants throughout the reserve and taken to the Horsham Orchid Facility to isolate the mycorrhiza. Thirty mycorrhizal isolates were successfully harvested and used for both propagation and phylogenetic analysis. Successful growth of the first germinants of Metallic Sun-orchid. Plants are now available for reintroduction into natural habitat.
As part of collaboration led by Dr Wright at the University of Melbourne preliminary sequencing revealed two species of mycorrhizal fungi (Tulasnella asymmetricaand Tulasnella violea-type) to associate and in subsequent experiments germinate (1 year old) Metallic Sun-orchids. Initial work undertaken includes 30 root samples across three sites being isolated for mycorrhizal fungi resulting in 90 mycorrhizal isolates. A weather station was installed, maintained and data on soil moisture and temperature at differing depths recorded. Monitoring established at three sites with associated vegetation being collected for tripartite propagation. Ninety isolates symbiotically sown with seed and mycorrhiza were sent to RMIT University for sequencing.
The Wimmera Orchid Lab. Lead by Dr Noushka Reiter from the Wimmera Catchment Management Authority has successfully raised 3000 Metallic Sun-orchids (see images) which are being introduced to four sites in south-west Victoria over the next 12 months, starting with two sites in the Little Desert National Park in July 2012. This is the first large scale reintroduction of an endangered orchid species in Australia. The project team includes the Australian Orchid Foundation, Australian Native Orchid Society, RMIT University, Royal Botanic Gardens Melbourne, Department of Environment and Primary Industries, Wimmera CMA and many enthusiastic volunteers.
Three 2 x 2m plots were established across the entire known population at Deaney’s Steps within the Port Campbell National Park in 2010. The Bay of Island Population was burnt in March 2011. An ecological burn of the population at Deaney’s Steps is scheduled for February / March 2012, which is in line with the recommended frequency / timing for this species. The area of the burn has been increased to include plants that were located outside the area burnt in 2005.
A post fire assessment of the Port Campbell Metallic Sun-orchid population was undertaken with assistance from Parks Victoria and the Timboon Field Naturalists Club in October 2014. One hundred and four plants were identified and spatially recorded throughout the burn area suggesting the burn achieved its intended objective.
An ecological burn at Flaxman’s Hill was conducted in March 2011, which was in line with the recommended frequency / timing for this species. The area of the burn was increased to include plants that were located outside the area burnt in 2005.
Surveying and caging of additional plants at Flaxman’s Hill was undertaken in partnership with International Student Volunteers in June 2011. During this survey, all uncaged flowering plants were identified and caged to minimise the risk of browsing from macropods and deer, a key threat at this site. The cages appear to be effectively protecting plants from grazing post-fire. There is scope to install more cages at the site, if uncaged orchids are seen to be impacted by grazing. The demographic monitoring transect was also completed during this visit. Results indicate less than one percent of the individual marked plants have emerged post-fire.
In 2013 DEPI conducted a strategic volunteer survey of the Grampians National Park and adjacent Grampians State Forest in bushfire affected areas. Approximately 135 previously unrecorded plants were spatially mapped and assessed at a new site which is highly significant for the conservation of this species.
A planned burn of 52 hectares of coastal heathland was undertaken in the Bay of Islands Coastal Park on the 22nd of March 2015 to promote and enhance the Metallic Sun-orchid population at this site. Post-fire monitoring of the population will be undertaken in Spring.
Volunteer-based threatened orchid surveys discovered a new sub-population of Metallic Sun-orchid in the Lake Mundi Wildlife Reserve.
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