Action Statement Flora and Fauna Guarantee Act 1988 No. 103 Twelve threatened Spider-orchids Caladenia species Description and distribution shrublands, heathlands, woodlands, heathy The genus Caladenia is represented in Victoria by woodlands and open forests. They are found 78 taxa. Of these, one taxon is considered extinct, generally in well-drained soils, including deep eighteen taxa are endangered, eight taxa are sands, sand and clay loams and dry skeletal soils. vulnerable and five taxa are considered rare. A The Spider-orchids addressed in this Action further fifteen taxa are poorly known but Statement occur in Grassy Dry Forests and Box- suspected to be in one of the above categories Ironbark Forests (C. amoena, C. audasii, C. (NRE 2000). rosella), coastal heathlands (C. hastata, C. This Action Statement addresses 12 threatened fragrantissima ssp. orientalis), near costal heathy (vulnerable or endangered) taxa of Caladenia and herb-rich woodlands (C. robinsonii, C. listed below. All taxa are members of the Genus thysanochila) and inland grassy, heathy or herb- Caladenia, Section Calonema, commonly referred rich woodlands (C. formosa, C. lowanensis, C. to as Spider-orchids. Taxa within this section are tensa, C. versicolor, C. xanthochila). characterised by their large, attractive flowers A defining feature of most of these habitats is with long filamentous segments often ending in that they are considered uncommon. This may be fine, elongated tips, which may be conspicuously due to these habitats having been naturally clubbed or densely covered, with dark-coloured uncommon prior to European settlement or more glandular hairs. Individual species’ descriptions typically because of clearing for agriculture and can be found in The Orchids of Victoria urbanisation since European settlement. Most (Backhouse and Jeanes 1995) and The Flora of species occur within severely fragmented Victoria Volume 2 (Walsh and Entwisle 1994). ecosystems that are subject to a range of The Spider-orchids addressed in this Action potentially threatening processes typical of such Statement occur over a wide area. Six taxa environments. (Caladenia formosa, Caladenia hastata, Caladenia lowanensis, Caladenia tensa, Caladenia Life history and ecology versicolor and Caladenia xanthochila) occupy All Spider-orchids are terrestrial, deciduous areas of western Victoria and south-east South herbs, emerging annually from spherical, Australia. Three taxa (Caladenia amoena, subterranean tubers that are protected by a Caladenia audasii and Caladenia rosella) occur in tough, fibrous tunic. Most plants shoot in central Victoria while the three remaining taxa response to soaking rains in early autumn, first (Caladenia fragrantissima ssp. orientalis, producing only a leaf that remains almost Caladenia robinsonii and Caladenia thysanochila) dormant through the winter. All of the taxa occupy coastal areas to the south-east of addressed by this Action Statement flower in late Melbourne. Distribution maps for each taxon are winter to spring. presented in the detailed species’ descriptions at Flowers may remain open for a few days to a few the end of this Action Statement. weeks depending on pollination and climatic Habitat factors. Fruits usually take 5-8 weeks to mature following pollination. Each mature capsule may Spider-orchids occupy a wide range of habitats contain tens of thousands of microscopic seeds throughout Victoria including alpine meadows, open mallee, shrublands, closed coastal that are dispersed by the wind when the capsule The role of fire in the ecology of the various dries out in early summer. Spider-orchid species is not known, but is likely to be an important factor, at least for some Most spider-orchids are believed to grow in a species which have exhibited strong flowering complex relationship with mycorrhizal fungi responses in the years following fire. The (Warcup 1981). The fungus assimilates some variation in seasonal climatic conditions, most nutrients for the orchid, but the degree of notably rainfall and temperature also influences dependence upon the fungus is not known. Most flowering. members of the Spider-orchid group are pollinated by sexual deception through a process Conservation status called pseudocopulation (Jones 1988). Spider- Each taxon has been listed under the orchids are characterised by the often large, Commonwealth Endangered Species Protection attractive flowers with long tapering sepals and Act 1992 and therefore is listed under the petals ending in clubs or covered with dark Commonwealth Environment Protection and glandular hairs that are the source of the sexual Biodiversity Conservation Act 1999. attractants for the pollinators, usually male Table 1 summarises the status of each taxon in thynnid wasps, attracted to the flowers by scent Australia (ANZECC 1999) and Victoria (NRE 2000) mimicking female thynnid wasp pheromone. and indicates status under the Victorian Flora Once it reaches the flower, the male attempts to and Fauna Guarantee Act 1988. copulate with the labellum of the flower, mistaking it for the female wasp, and effects Decline and threats pollination. The identities of the pollinator(s) for most species are not known. While thynnid Most of the Caladenia taxa addressed in this wasps are the most likely pollinators, a small Action Statement have been described in the last native calictid bee (Neoproctus species) has been ten years, the exceptions being C. audasii, C. reported as a pollinator of the Rosella Spider- hastata and C. rosella. For the recently described orchid Caladenia rosella (C. Beardsell pers. taxa, most have been split from larger complexes comm.). Observations suggest that the period and hence little information is known of their available for effective pollination may be quite former range, whether their range has declined short, maybe only a few days. Successful and if so, the rate of decline. For some taxa (eg. pollination may be influenced by the receptivity Caladenia thysanochila), it is likely that they once of the stigma to pollen, the number of pollinators occupied a very restricted habitat and range in an area, insect behaviour and climatic while for other taxa (eg. Caladenia formosa), the conditions. species may have once been present over thousands of square kilometres. Table 1: Conservation Status Scientific name Australia Victoria FFG Caladenia amoena EeL Caladenia audasii EeL Caladenia formosa VvL Caladenia fragrantissima ssp. orientalis EeL Caladenia hastata EeL Caladenia lowanensis EeL Caladenia robinsonii+ EeL Caladenia rosella EeL Caladenia tensa EeL Caladenia thysanochila+ EeL Caladenia versicolor VvN Caladenia xanthochila EeL Abbreviations: Australia: E=endangered in Australia; V=vulnerable in Australia; Victoria: e=endangered in Victoria; v=vulnerable in Victoria; FFG: L=listed on Schedule 2 of the FFG Act; N=nominated for listing under the FFG Act. This information is important for assessing of their near-coastal habitat. These taxa now threats to known populations, when developing occupy areas close to and within urban actions to counter-balance these threats and development and the subsequent impacts when looking at broader remedial actions such as associated with this and the management plant re-introductions and trans-locations. The constraints placed on these sites are the largest twelve Caladenia taxa are listed as threatened for threats to extant populations of these taxa. varied reasons. Most of the taxa have small Populations of the twelve threatened Caladenia distributions, restricted habitats and a large taxa are currently under threat from a variety of proportion of their total population occurs at one sources of varying magnitude and concern. The or a few locations. Most taxa (C. amoena, C. major issues are weed invasions, grazing by audasii, C. fragrantissima ssp. orientalis, C. introduced and native herbivores, inappropriate hastata, C. lowanensis, C. robinsonii, C. rosella, C. fire regimes and habitat disturbance. The risk thysanochila, C. versicolor and C. xanthochila) posed to extant populations by these threats may also have small total populations. vary depending on geographical, environmental, The single biggest issue for the decline of most biological and social factors. Threats may be of the taxa is habitat destruction. Five of the taxa acting singularly or in series to present a risk to (C. formosa, C. lowanensis, C. tensa, C. versicolor populations. and C. xanthochila) occupy broad riverine plains habitats (of central and western Victoria) on Existing conservation measures reasonably fertile soils that have been cleared Reservation over large parts of their range for agricultural production. Extant populations tend to occupy Representation of the Caladenia taxa in fragmented forests and woodlands within largely conservation reserves varies from well agricultural landscapes and it is this represented to not reserved. Examples include C. fragmentation and the associated site lowanensis and C. tensa, which have a very high degradation arising from it, that may now proportion of their total population represented represent the greatest threat to the long-term within conservation reserves while C. amoena, C. conservation of these species. Habitat of C. fragrantissima ssp. orientalis, C. robinsonii, C. amoena, C. audasii and C. rosella has been versicolor and C. xanthochila are unreserved severely reduced and altered by historic mining across their range. Caladenia formosa is reserved activities and more recent urban development. in South