Species Profile and Threats Database

For information to assist proponents in referral, environmental assessments and compliance issues, refer to the Policy Statements and Guidelines (where available), the Conservation Advice (where available) or the Listing Advice (where available).
In addition, proponents and land managers should refer to the Recovery Plan (where available) or the Conservation Advice (where available) for recovery, mitigation and conservation information.

EPBC Act Listing Status Listed as Endangered
Listing and Conservation Advices Commonwealth Listing Advice on Caladenia williamsiae (Threatened Species Scientific Committee, 2006co) [Listing Advice].
Commonwealth Conservation Advice on Caladenia williamsiae (Threatened Species Scientific Committee, 2008zi) [Conservation Advice].
Recovery Plan Decision Recovery Plan not required, included on the Not Commenced List (1/11/2009).
Adopted/Made Recovery Plans
Policy Statements and Guidelines Draft survey guidelines for Australia's threatened orchids (Department of the Environment, 2013b) [Admin Guideline].
Federal Register of
    Legislative Instruments
Inclusion of species in the list of threatened species under section 178 of the Environment Protection and Biodiversity Conservation Act 1999 (45) (14/08/2006) (Commonwealth of Australia, 2006j) [Legislative Instrument].
State Government
    Documents and Websites
WA:Interim Recovery Plan. No. 277. Williams' Spider Orchid (Caledenia williamsiae) Interim Recovery Plan 2007-2012 (Western Australia Department of Environment and Conservation (WA DEC), 2007d) [State Recovery Plan].
State Listing Status
WA: Listed as Critically Endangered (Wildlife Conservation Act 1950 (Western Australia): September 2013 list)
Scientific name Caladenia williamsiae [68732]
Family Orchidaceae:Orchidales:Liliopsida:Magnoliophyta:Plantae
Species author Hopper & A.P.Brown
Infraspecies author  
Reference Nuytsia 14: 393-304 (2001)
Distribution map Species Distribution Map

This is an indicative distribution map of the present distribution of the species based on best available knowledge. See map caveat for more information.

Illustrations Google Images

Scientific name: Caladenia williamsiae (Hopper & Brown 2001).
Common name: Williams Spider Orchid (CALM 2005).

The Williams Spider Orchid is usually solitary, growing to 15-20cm tall. The leaf is erect, broadly linear, 7-9 cm x 15-18 mm and pale green. The spider-like flowers are yellow-green (Hopper & Brown 2001).

The Williams Spider Orchid is endemic to Western Australia and known from three subpopulations within the same reserve near Brookton approximately 135 km south-east from Perth (CALM 2005).

Two subpopulations are located approximately 1.7 km from the third subpopulation. Therefore the extent of occurrence for the Williams Spider Orchid is estimated to be approximately 1.7 km² (CALM 2005).

There is little data available on possible past decline in extent of occurrence of the Williams Spider Orchid. However, the nature reserve in which this species occurs is located in a largely cleared area of the West Australian Wheatbelt, indicating that the species may have been more widespread in the past (CALM 2005).

The current area of occupancy of the Williams Spider Orchid is 0.002909 km² across the three known populations.

Population 1: 14 Plants in 3 x 3 m (23/9/03)

Population 2:102 plants in 70 x 30 m (23/9/03)

Population 3: 27 plants in 40 x 20 m (23/9/03)

There is little data available to ascertain if there has been a past decline in area of occupancy of this species (CALM 2005).

The three known populations of the Williams Spider Orchid are in close proximity to each other and occur within a Nature Reserve. Therefore, they are not considered to be fragmented (CALM 2005).

There are no translocated populations of the Williams Spider Orchid. However, germplasm material has been collected by the Botanic Parks and Gardens Authority (CALM 2005).

CALM Officers have been involved in a number of surveys in an attempt to locate further populations of the Williams Spider Orchid. No additional populations have been located since 2003 (CALM 2005).

Several other reserves between Weam and Boyagin have been targeted for survey as they contain similar habitat to the Williams Spider Orchid, but no further plants were found. Further surveys will be conducted in August to September 2005 (CALM 2005).

The total population size of the Williams Spider Orchid is 143 mature individuals.

Population 1: 14 plants (healthy 29.08.03)

Population 2: 102 plants (healthy 29.08.03)

Population 3: 27 plants (healthy 29.08.03) (CALM 2005).

Only partial information is available for the population trend for the Williams Spider Orchid. The data available indicates that there has been an increase in the known population size for this species as a result of more thorough survey. The number of Williams Spider Orchid plants known from the wild has ranged from 11 mature plants in 2000, to 6 in 2001 for population 1, which appears to be in decline. However, with the discovery of a further two populations, the total known number of mature plants has increased to 143 when last surveyed in 2003 (CALM 2005).

All three known populations of the Williams Spider Orchid occur within the Weam Nature Reserve and are managed by CALM.

The Williams Spider Orchid has been recorded in open Wandoo/Jarrah woodland over scattered open shrubs in red loamy earth (Hopper & Brown 2001).

Species associated with the Williams Spider Orchid include: Hypocalyma angustifolium, Acacia pulchella and Hibertia exasperata (CALM 2005).

The flowering period for the Williams Spider Orchid is from August to September. It is thought that Thynnid wasps are the pollinators of this species because of its floral architecture (CALM 2005).

The dark yellow/green colouration of this species' flowers makes it difficult to see in the wild (Hopper & Brown 2001). Its short broad leaf, and small greenish-yellow flowers with four rows of calli on the labellum and sepals abruptly narrowed below the osmophore are characters not seen elsewhere in Caladenia subgenus Calonema (Hopper & Brown 2001).

Any additional survey for the Williams Spider Orchid should be focused on remnant vegetation in similar soil and vegetation types. Surveys would be easier during the flowering period from August to early September as individuals would be more conspicuous (CALM 2005).

Population Past Present Future
1 Land Clearing Fire/Kangaroo Grazing Fire
2 Land Clearing Fire Fire
3 Land Clearing Fire Fire

In the past land clearing would have been the main threat to the survival of the Williams Spider Orchid.

Currently, fire is a potential threat to the known populations and the species response to fire is unknown.

Evidence of grazing on flowers buds by Kangaroos was noted for population 1. However, populations 2 and 3 have not been subject to grazing pressure by kangaroos (CALM 2005).

The Williams Spider Orchid has a similar flower morphology to Caladenia species that are pollinated by male thynnid wasps and it is thought that it too is likely to use sexual deception to attract wasps as pollinators. Thynnid wasps feed on native plant species which must be present to provide suitable habitat for viable populations of the wasp to survive. Like other native orchids, once pollinated, it produces thousands of wind dispersed seeds which must land in an area that contains the correct mycorrhizal fungus in order to germinate. Further studies are required in order to ascertain if any of these factors may result in future change to the species population (CALM 2005).

It has been proposed that putting a small cage over the plants at population 1 will be of use in preventing grazing by kangaroos (CALM 2005).

The populations may need to be protected from unauthorised collectors. Narrogin District Office proposes to place a padlock on reserve gate to restrict entry access (CALM 2005).

The species was first described by Hopper & Brown (2001).

The Williams Spider Orchid is not described in any current recovery or conservation plans. However, as this species is currently ranked as Critically Endangered, an Interim Recovery Plan will be prepared for this species in accordance with CALM Draft Policy Statement 9 (CALM 2004).

The following table lists known and perceived threats to this species. Threats are based on the International Union for Conservation of Nature and Natural Resources (IUCN) threat classification version 1.1.

Threat Class Threatening Species References
Biological Resource Use:Gathering Terrestrial Plants:Illegal collection Commonwealth Conservation Advice on Caladenia williamsiae (Threatened Species Scientific Committee, 2008zi) [Conservation Advice].
Ecosystem/Community Stresses:Indirect Ecosystem Effects:Restricted geographical distribution (area of occupancy and extent of occurrence) Commonwealth Listing Advice on Caladenia williamsiae (Threatened Species Scientific Committee, 2006co) [Listing Advice].
Invasive and Other Problematic Species and Genes:Problematic Native Species:Competition, predation and/or habitat degradation by kangaroos and wallabies Commonwealth Conservation Advice on Caladenia williamsiae (Threatened Species Scientific Committee, 2008zi) [Conservation Advice].
Natural System Modifications:Fire and Fire Suppression:Inappropriate and/or changed fire regimes (frequency, timing, intensity) Commonwealth Conservation Advice on Caladenia williamsiae (Threatened Species Scientific Committee, 2008zi) [Conservation Advice].
Species Stresses:Indirect Species Effects:Low numbers of individuals Commonwealth Listing Advice on Caladenia williamsiae (Threatened Species Scientific Committee, 2006co) [Listing Advice].

CALM (2004). Draft Policy Statement No 9. Conserving Threatened Species and Ecological Communities (Revised). Western Australian Department of Conservation and Land Management.

Hopper, S.D. & Brown, A.P. (2001a). Contributions to Western Australian orchidology: 1. History of early collections, taxonomic concepts and key to genera. Nuytsia. 14:1-26.

IUCN (2001). IUCN Red List Categories and Criteria version 3.1. IUCN, Gland Switzerland.

Western Australian Herbarium (2005). FloraBase - The Western Australian Flora. [Online]. Perth, Western Australia: Department of Conservation and Land Management. Available from:

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This database is designed to provide statutory, biological and ecological information on species and ecological communities, migratory species, marine species, and species and species products subject to international trade and commercial use protected under the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act). It has been compiled from a range of sources including listing advice, recovery plans, published literature and individual experts. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. Individuals and organisations should consider all the available information, including that available from other sources, in deciding whether there is a need to make a referral or apply for a permit or exemption under the EPBC Act.

Citation: Department of the Environment (2014). Caladenia williamsiae in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: Accessed Sun, 21 Sep 2014 03:04:54 +1000.