The Spiral Sun-orchid has a slender green flower stem growing to 20 cm tall. Flowers are solitary and bluish purple with darker stripes, its column being purplish with a bright yellow tip.
Spiral Sun-orchid |
Status: Vulnerable on the EPBC Act list
Government evidence of impact of climate change:
Australian Government, Conservation Advice, Thelymitra matthewsii
Climate change Increased frequency and Timing current Climate projections for south eastern severity of bushfires Confidence suspected Australia include reduced rainfall; increased average temperatures; and Consequence moderate more frequent bushfires (CSIRO Trend increasing Bureau of Meteorology 2015).
Identify current and future habitat modelled as likely to remain or become suitable habitat due to climate change.
Fire ecology The Spiral Sun orchid does not require fire to stimulate flowering or for reproduction and; although its underground tuber is capable of surviving fire; recent observations suggest it can be adversely impacted by intense fire; possibly due to tubers being located at a relatively shallow depth in the soil.
This suggests the impacts of high intensity fire are variable and possibly specific to the site or fire conditions.
The heathy woodland or mixed eucalypt forest communities in which the Spiral Sun orchid grows are likely to have minimum recommended fire intervals of 15 25 years (Cheal 2010); although minimum tolerable fire intervals for the Spiral Sun orchid are not well understood.
Extent across the entire range Analysis by the Wildlife and Threatened Species Bushfire Recovery Expert Panel; based on intersecting the modelled distribution of the Spiral Sun orchid and the National Indicative Aggregated Fire Extent Dataset; indicates that approximately 5 of the range of the species was within the extent of the 2019 20 bushfires (Gallagher 2020).
If planned fire is used to maintain habitat for Spiral Sun orchid; careful attention should be given to frequency and timing of fire; as orchids are generally best adapted to survive fires during their dormancy period in late spring to early autumn; while fires from late autumn to early spring (when the orchid is above ground) may be damaging to plants (Jasinge et al. 2018).
Any use of fire should take into account impacts on other species that may be impacted by its use.
Take the likelihood of increasingly frequent bushfires into account when developing planned burning programs; to avoid excessively frequent burning of any subpopulations.
Seed collections should be sensitive to the likely importance of post fire germination in maintaining wild subpopulations.
Engage with agencies undertaking planned burning operations to ensure they are aware of the locations of these subpopulations and have access to sensitive or restricted records on relevant databases.
Extent across its entire range In drought years sun orchids often do not flower (Bates 2010) and it is likely that an increasing frequency of droughts will have a negative impact on orchids generally (Coates et al. 2006).