The Minister included this species in the vulnerable category, effective from 14/05/2013

Advice to the Minister for Sustainability, Environment, Water, Population and Communities from the Threatened Species Scientific Committee (the Committee) on Amendment to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)

1. Reason for Conservation Assessment by the Committee This advice follows assessment of new information provided through the Species Information Partnership with Western Australia on: nigrum (shield-back )

2. Summary of Species Details Conventionally accepted as Idiosoma nigrum Main, 1952 State Listing Status Listed as Schedule 1 Fauna (fauna that is rare or likely to become extinct) under the Western Australian Wildlife Conservation Act 1950. Managed as vulnerable by the Western Australian Government. Description The shield-back spider is a large spider; females may be 30 mm in body length and males up to 18 mm in body length. The species is dark brown to black in colour and is easily recognisable by the distinctive structure of the abdomen. The abdominal cuticle or skin is thick and hard. The end of the abdomen is flattened and shield-like, and its sides are deeply grooved giving them a rugose, corrugated appearance (DEWHA, 2010). Distribution Endemic to Western Australia. The species is known from three locations. One location consists of a number of severely fragmented populations in the central and northern wheatbelt (Main et al., 2000). The second and third locations are at Jack Hills and Weld Range, two isolated populations approximately 200 km further north, in more arid areas (Main, pers. comm., 2009). The shield-back spider occurs over a range of land tenures including private property, pastoral leases, nature reserves, Crown reserves, road verges and mining tenements (Clark and Spier, 2003; DEC, 2010). Relevant The shield-back spider typically inhabits clay soils of eucalypt Biology/Ecology woodlands and acacia vegetation, and relies heavily on leaf- litter and twigs to build its (Main, 1996, 2003). The species is very well-adapted for life in semi-arid habitats. It lives in that are tubular and approximately 20–30 cm deep (Main, 1992). The burrow is deep enough to ensure that air in the lower burrow remains humid and relatively cool in summer. The burrow has a lightweight trapdoor of leaf-litter and silk, with a fan of leaf and twig trip-lines attached to the burrow rim. Movement of a trip-line alerts the spider waiting in the entrance of the burrow to the presence of prey, which is primarily , but also includes , , and (Clark and Spier, 2003; DEWHA, 2010). Females spend their entire life in the burrow or within its proximity. Gene flow is therefore facilitated by male biased

Idiosoma nigrum (shield-back spider) Listing Advice Page 1 of 6 The Minister included this species in the vulnerable category, effective from 14/05/2013

dispersal, estimated to be less than 500 m (Main, unpublished data), as only males leave their burrows in search of females. The species aestivates (becomes dormant) during the drier months of the year, from November to February (Main, pers. comm., 2009). Threats Known Land clearing has had a severe impact on the populations in the central and northern wheatbelt. Land clearing has caused the species’ occurrence to become severely fragmented in areas of remnant bushland (Main, 2003; DEC, 2010). Salinisation is widespread across the entire wheatbelt and is a threat to the populations in this area. Salinisation affects lower- lying remnant vegetation, as the saline water kills the plants and therefore affects the , which rely on the vegetation and associated leaf-litter for habitat (Main, pers. comm., 2009; DEC, 2010). Grazing affects the species’ habitat across its range (DEC, 2010). Grazing by stock and feral , such as goats and rabbits, causes deterioration of the leaf litter and hence the habitat that the spiders dwell in. Observations made at Weld Range show that areas where stock have grazed have fewer juveniles and emergents relative to adult shield-back spiders, compared to areas where stock has never been allowed to graze (Davies, pers. comm. to BY Main, 2009). Potential Dust pollution from mine exploration activities may have affected the two populations at Jack Hills and Weld Range as exploration for mining has occurred within these populations. The construction and operation of an active mine typically generates fine dust, which settles on the surrounding area, including vegetation. This can cause serious damage to vegetation and lead to a reduction in vegetation, followed by a decline in invertebrate fauna. For the shield-back spider, both processes are important as they may result in a loss of suitable habitat and prey (Davies, pers. comm. to BY Main, 2009). Vibration from mine exploration activities may have affected the two populations at Jack Hills and Weld Range as exploration for mining has occurred within these populations. The vibration caused by mining equipment is likely to affect invertebrates in shallow burrows. Vibration assessments showed that vibrations from some mining equipment carried up to 600 m (Ecologia Environment, pers. comm. to B.Y Main). Inappropriate fire regimes may be a potential threat to the shield-back spider. It has been shown in another trapdoor spider (Anidiops villosus), with similar dispersal patterns to the shield- back spider, that removal of the understorey and litter layer by fire can lead to local extinction, with limited potential for recolonisation from nearby patches (Main, 1957, 1991, 1992, 1995; Yen, 1995).

Idiosoma nigrum (shield-back spider) Listing Advice Page 2 of 6 The Minister included this species in the vulnerable category, effective from 14/05/2013

3. Public Consultation Notice of the proposed amendment was made available for public comment for 30 business days. Any comments received that are relevant to the survival of the species have been considered by the Committee.

4. How judged by the Committee in relation to the EPBC Act criteria and Regulations

Criterion 1: It has undergone, is suspected to have undergone or is likely to undergo in the immediate future a very severe, severe or substantial reduction in numbers. Not eligible Criterion element Evidence Reduction in numbers Insufficient data – There are insufficient data to support a past or projected reduction in numbers over a timeframe relevant to this criterion. However, the species is suspected to be declining. Observations at several sites indicate that some populations within the wheatbelt have declined. Data from a study area in the East Yorkrakine Reserve (one of the fragmented populations in the wheatbelt) between 1989 and 1999 showed a 95 per cent decline in the population (Main, 2003). However, while the species is suspected to be declining at several sites within the wheatbelt, the magnitude of this decline across the species’ broader range is difficult to quantify, due to a lack of data.

Criterion 2: Its geographic distribution is precarious for the survival of the species and is very restricted, restricted or limited. Eligible for listing as vulnerable Criterion element Evidence Geographic distribution Limited – The species’ area of occupancy is estimated to be 1 700 km2 and its extent of occurrence is approximately AND 21 500 km2 (Main, unpublished data). Geographic distribution Yes – The populations that occur in the central and northern precarious wheatbelt are severely fragmented, and the two populations at Jack Hills and Weld Range are geographically isolated. Due to the limited dispersal ability of the species, there is no possibility of demographic or genetic exchange between populations. Continued decline is inferred due to ongoing threats (Main, 2003; DEC, 2010).

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Criterion 3: The estimated total number of mature individuals is very low, low or limited; and either (a) evidence suggests that the number will continue to decline at a very high, high or substantial rate; or (b) the number is likely to continue to decline and its geographic distribution is precarious for its survival Not eligible Criterion element Evidence Total no. of mature Insufficient data – There are no estimates of the total number individuals of mature individuals (DEC, 2010). AND Continued rate of decline No data. OR Total no. of mature Insufficient data – see above. individuals AND Continued decline likely Yes – see Criterion 2. AND Geographic distribution Yes – see Criterion 2. precarious

Criterion 4: The estimated total number of mature individuals is extremely low, very low or low Not eligible Criterion element Evidence Total no. of mature Insufficient data – see Criterion 3. individuals

Criterion 5: Probability of extinction in the wild that is at least (a) 50% in the immediate future; or (b) 20% in the near future; or (c) 10% in the medium-term future Not eligible Criterion element Evidence Probability of extinction in No data. the wild

5. Recovery Plan There should not be a recovery plan for the shield-back spider as the approved conservation advice for the species provides sufficient direction to implement priority actions and mitigate against key threats.

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6. Recommendations (i) The Committee recommends that the list referred to in section 178 of the EPBC Act be amended by including in the list in the vulnerable category: Idiosoma nigrum (ii) The Committee recommends that there should not be a recovery plan for this species.

Threatened Species Scientific Committee 1 June 2010

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References cited in the advice Clark GM and Spier F (2003). A Review of the conservation status of selected Australian non-marine invertebrates. Idiosoma nigrum (shield-backed trapdoor spider), 60–63. Viewed: 25 January 2010 Available on the Internet at: http://www.environment.gov.au/biodiversity/threatened/publications/action/non-marine- invertebrates/index.html Davies M (Ecologia Environment) (2009). Personal communication to BY Main, University of Western Australia. Department of Environment and Conservation (DEC) (2010). Records held in DEC’s declared fauna database and rare fauna files. Western Australian Department of Environment and Conservation, Western Australia. Department of the Environment, Water, Heritage and the Arts (DEWHA) (2010). Species Bank – Idiosoma nigrum Viewed: 20 January 2010 Available on the Internet at: http://www.environment.gov.au/cgi-bin/species-bank/sbank- treatment.pl?id=66798 Main BY, unpublished data. School of Biology, The University of Western Australia. Main BY (1952). Notes on the genus Idiosoma, a supposedly rare Western Australian trap- door spider. The Western Australian Naturalist, 3: 130–136. Main BY (1957). Biology of Aganippine trapdoor spiders (Myglomorphae: Ctenizidae). Australian Journal of Zoology, 5: 402–473. Main BY (1991). Trapdoor spiders in remnant vegetation of the Western Australian wheatbelt. WEB (National Bulletin) 2: 8–9. Main BY (1992). The role of life history patterns and demography of mygalomorph trapdoor spiders for assessing persistence in remnant habitats of the Western Australian Wheatbelt. Report for the World Wide Fund for Nature, World Wide Fund for Nature, Sydney. Main BY (1995). Survival of trapdoor spiders during and after fire. CALM Science Supplement, 4: 207–216. Main BY (1996). Microcosmic biogeography: trapdoor spiders in a time warp at Durokoppin p. 163–171 in (eds SD Hopper, JA Chappill, MS Harvey, AS George) Gondwanan Heritage: past, present and future of the Western Australian biota, Chipping Norton, NSW, Surrey Beatty & Sons. Main BY (2003). Demography of the shield-back trapdoor spider Idiosoma nigrum Main in remnant vegetation of the Western Australian wheatbelt. Records of the South Australian Museum, Monograph Series. 7: 179–185. Main BY (2009). Personal communications related to the preparation of this document, 10 November 2010. The University of Western Australia. Main BY, Sampey A and West PJL (2000). Mygalomorph spiders of the southern Carnavon Basin, Western Australia. Records of the Western Australian Museum, 61: 281–293. Yen AL (1995). Australian spiders: an opportunity for conservation. Records of the Western Australian Museum, Supplement 52: 39–49. Magdalena Davies (Ecologia Environment) personal communication to B.Y.Main”

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