Sunshine Diuris Diuris Fragrantissima
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Action Statement Flora and Fauna Guarantee Act 1988 No. 50 (revised in 2004) Sunshine Diuris Diuris fragrantissima Preamble The species is most similar to the Wedge This Action Statement is heavily based on the Diuris Diuris dendrobioides Fitzg., a threatened draft Recovery Plan under the Environment orchid from grasslands in inland western New Protection and Biodiversity Conservation Act South Wales and northern Victoria. The 1999 prepared for this species by the Wedge Diuris was included in D. Department of Sustainability and Environment fragrantissima by Walsh and Entwistle (1994), for the Commonwealth Department of although most other authors including Jones Environment and Heritage. (1988), Clements (1989), Gullan et al. (1990), Backhouse and Jeanes (1995) and Bishop Description (1996) have retained D. dendrobioides as a Sunshine Diuris has two to three slender, separate species. channelled, grass-like green leaves, up to 18 cm long. A slender green stem to 20 cm tall, bears Distribution and abundance one to nine (average four) strongly scented Sunshine Diuris was once so common in the flowers, coloured white with variable purplish native grasslands north-west of Melbourne hues and streaks, while the lateral sepals are around the time of European occupation, that green. The dorsal sepal is triangular and erect, it was often referred to as ‘Snow-in-the- while the lateral sepals are long and slender (to Paddocks’ (Richards 2002). Since then the about 60 mm), inrolled, drooping and parallel species has suffered a catastrophic decline in (giving rise to the name doubletail). The ovate range and abundance. Its decline has been petals project obliquely upwards. The labellum attributed to widespread habitat destruction is strongly bilobed, the lateral lobes curved and degradation. Current major threats upward, and the fan-shaped mid-lobe projects include weed invasion, predation from forward. Flowers open sequentially up the stem, introduced herbivores, lack of fire and ill- the lowest flower often having collapsed before timed fire. the top flower buds have opened. Sunshine Diuris is now known from only two The Sunshine Diuris was originally called the populations in the wild, at Tottenham and White Diuris, Diuris alba R. Br., a species now Laverton North, although the latter is the known to be confined to the central coast of result of reintroduction. There are believed to New South Wales (Bishop 1996). It was later be fewer than 5 plants in the wild. There are known as the white form of the Purple Diuris 800-1000 plants in cultivation, principally at (Diuris punctata var. albo-violacea Rupp ex the Melbourne Zoo but also at the Royal Dockr.) until it was recognised and described as Botanic Gardens and with private growers a separate species, D. fragrantissima D.L. Jones et M.A. Clem. (cited in Clements 1989). The Tottenham site is owned by Victorian Rail Very little is known of the biology or ecology of Track (Victrack), a Victorian Government Business Sunshine Diuris. It grows in a complex Enterprise. The reintroduction site at Laverton relationship with a mycorrhizal fungus Tulasnella North Grassland Reserve is managed by Parks calospora Boudier (Warcup 1971), that initiates Victoria under the Victorian Crown Land (Reserves) seed germination, and assimilates nutrients for the Act 1978 (Parks Victoria 2000). The site is orchid. The degree of dependence upon the reserved under the IUCN category IV for the fungus, particularly of mature plants, is not purpose of nature conservation (International known. Some individuals of Sunshine Diuris have Union for the Conservation of Nature 1994; Parks survived for over nine years in the wild (Cropper Victoria 2000). 1993) and over 20 years in cultivation (D. Tonkinson, La Trobe University and C. Knight, Habitat Melbourne Zoo, unpubl. data). Sunshine Diuris appears to have been confined to Sunshine Diuris is pollinated by a small native bee the grassland plains immediately to the west of (Tonkinson 1985), the purplish colour of the Melbourne, particularly between Werribee and flowers mimicking the colour of native lilies that Sydenham (Cropper 1993; Jones 1988; Parsons often grow with Diuris species. The bee may also 1981). It grew in native grasslands dominated by be attracted by the strong fragrance of the orchid. Kangaroo Grass Themeda triandra, on heavy basalt Cropper (1993) reported very low natural rates of soils, often with embedded basalt boulders. The pollination, with a maximum of only 7% of flowers sole remaining natural population occurs in a producing seed pods, which is possibly a function small (one hectare) grassland remnant located of the rarity of the orchid and hence few along a railway reserve west of Melbourne. T. opportunities for pollinators to find flowers and triandra dominates this site with Austrodanthonia effect pollination. species, Dianella longifolia, Dianella revoluta, Hot summer fires are likely to enhance flowering in Tricoryne elatior, Pimelea humilis and Dichanthium the following flowering season. Fires may species (the latter may be a non-endemic native indirectly promote seed germination and seedling plant transported to the site). establishment by altering soil nutrient levels and The sole remaining natural population at by reducing competition from associated grasses. Tottenham is found in Western (Basalt) Plains This effect may act directly upon the orchid, or Grassland on shallow clay with exposed basalt indirectly through the fungal symbiont. Most boulders. This site, as well as the reintroduction recruitment has been observed one to two years site at Laverton North Grassland Reserve should be after a summer fire. considered as part of the critical habitat for the species, although there remains some doubt as to Conservation status whether they still fulfil the ecological requirements for the species. There is some suggestion that National conservation status Sunshine Diuris may have had a wider distribution Sunshine Diuris has been listed as Endangered and ecological range than at present (Richards under the Commonwealth Environment Protection 2002). This could indicate that Sunshine Diuris and Biodiversity Conservation Act 1999. may be able to tolerate a wider ecological niche than that which it currently occupies. Using the IUCN Red List categories and criteria (2001), Sunshine Diuris is Critically Endangered Life history and ecology and is close to extinction in the wild. An application has been made to revise the status of Sunshine Diuris is a terrestrial deciduous herb, the species from Endangered to Critically emerging annually from a lobed, subterranean Endangered sensu IUCN (2001). tuber. The leaves emerge in late autumn, following the onset of seasonal rains. Flowering commences in late October, through November and is Victorian conservation status completed by early December. Sunshine Diuris has been listed as threatened under the Flora and Fauna Guarantee Act 1988. By mid-summer the leaf has shrivelled, and if pollination has occurred, the seed capsule is Sunshine Diuris is considered Endangered in ripening. Seed set occurs about six weeks after. Victoria according to “Advisory List of Rare or The species survives the late summer and early Threatened Vascular Plants in Victoria – 2004” autumn as a dormant tuber. Reproduction is (DSE 2004). almost entirely from seed, with rare vegetative reproduction apparently possible (Cropper 1993). The irregularly shaped, lobed tuber is replaced annually. 2 Decline and threats by the introduced House Mouse Mus musculus, was Sites where Sunshine Diuris occurred have now believed responsible for a mortality of perhaps 70% been destroyed, with the exception of the of plants during the mid-1980s (Cropper 1993). Tottenham Rail reserve and the translocation site Trampling, particularly by visiting naturalists, has at Laverton North Grassland Reserve. Prior to its been a major problem in the past, with up to 15% near extinction in the wild, botanists had been of plants broken or damaged in some years concerned with the plight of Sunshine Diuris for (Cropper 1993). Human interference with the almost 80 years. In 1934, Nicholls (Willis 1951) reserve is also cause for concern. Three days after wrote that 'the species was at one time exceedingly the flowering plant was found in 1997, the plentiful, but is now becoming scarce'. Willis grassland reserve was deliberately burnt by an (1951) believed that 'Victoria's most beautiful arsonist. Ironically, this event may have been the orchid' was in dire peril of extinction. stimulus for three plants flowering in 1998. By 1970, only five D. fragrantissima populations However, while fires occurring in late summer are remained, and by 1980 the species was restricted beneficial to the species, too frequent or ill timed to the single remaining site at Tottenham rail fire may be a threat, causing damage to plants, reserve, where about 100 plants survived. This increasing seedling mortality and destroying population continued to decline through the immature seedpods. It is highly likely that, with so 1980s, with 67 flowering plants recorded in 1982, few plants, ecological processes such as natural 11 in 1989, and only one in 1992. No flowering pollination have also been substantially disrupted. plants were seen in recent years, until a single flowering plant was found at the site in October Existing conservation measures 1997. A short time later an arsonist set fire to the The plight of Sunshine Diuris has received reserve, and three flowering plants were recorded