Conservation Advice on 14 Oct 2015; and Included This Species in the Endangered Category, Effective from 22 Oct 2015
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The Minister approved this conservation advice on 14 Oct 2015; and included this species in the Endangered category, effective from 22 Oct 2015. Conservation Advice Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) A saltbush Taxonomy Conventionally accepted as Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) Western Australian Herbarium (a saltbush). Summary of assessment Conservation status The highest category for which Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) is eligible to be listed is Endangered under Criterion 2 (B1, B2, (a) and (b)(i), (ii), (iv)). It is also eligible for listing as Vulnerable under Criterion 1 (A3 (c)). Species can be listed as threatened under state and territory legislation. For information on the listing status of this species under relevant state or territory legislation, see http://www.environment.gov.au/cgi-bin/sprat/public/sprat.pl Reason for conservation assessment by the Threatened Species Scientific Committee This advice follows assessment of information originally provided by Western Australia as part of the process to systematically review species that are inconsistently listed under the EPBC Act and relevant state legislation. Public Consultation Notice of the proposed amendment and a consultation document was made available for public comment for 37 business days between 24 November 2014 and 16 January 2015. Any comments received that were relevant to the survival of the species were considered by the Committee as part of the assessment process. Species/Sub-species Information Description Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) is a subdioecious plant distinguished by its dome shaped habit and divaricate woody branches. Female plants have distinctive fan-like fruits (with or without appendages). The species is an erect, subdioecious (with separate female and male plants; however, many male plants also have scattered female flowers in the lower branches) perennial shrub 0.4–1 m high with divaricate woody branches. Branchlets scruffy with collapsed vesicular hairs, glabrescent. Leaves scattered along branches or in clusters; petiole absent or to 0.3 mm long; lamina broadly elliptic to ovate, 0.8–6.5 mm long, 0.9–3.2(–5.3) mm wide with a dense indumentum of collapsed vesicle hairs forming a fused uneven surface, margin entire or sinuate to shallowly dentate. Male flowers in small, terminal glomerules or short panicles 3–10 mm long, 2.9–4 mm wide; bracteoles (leaf-like structures) absent; perianth 5-lobed, lobes elliptic 1.5– 1.9 mm long, 0.6–0.9 mm wide, fused in the lower half, with a rounded apex; staminal filaments five, filaments 1–1.8 mm long, 0.2–0.3 mm wide, anthers oblong, 0.4 mm long, 0.45 mm wide, yellow, becoming reddish with age, pollen yellow. Female flowers solitary, borne in leaf axils; perianth absent; bracteoles 2, sessile or with a short stipe 0.8–0.9 mm long, valves obovate 1.5– 4.4 mm long, 0.9–3.7 mm wide, equal in length, fused for lower half to two-thirds, outer surface Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) (a saltbush) Conservation Advice Page 1 of 8 smooth or later developing finger-like appendages, apex sinuate to dentate; stigmas 2, filiform 0.6–1.5 mm long, minutely plumose. Fruiting bracteoles sessile or with a thickened base 0.9– 1.7 mm long, 0.7–1.8 mm mm long; valves broadly obovate to fan shaped 4.5–7 mm long, 4–7.4 mm wide, becoming hardened with a swollen, spongy outer layer; outer surface smooth or with finger-like appendages on both sides, apex broadly dentate. Seeds rounded to broadly ovate in outline, brown, unornamented 0.9–1.4 mm long, 1.0–1.4 mm wide. The two populations of Atriplex sp. (Yeelirrie Station) possess similar levels of genetic diversity, but exhibit a high level of genetic differentiation given their proximity (Clark et al. 2012; Shepherd et al., submitted). Distribution During surveys for BHP Billiton’s Yeelirrie Uranium project, consultants from Western Botanical collected what was thought to be a new species of Atriplex. In September 2009 specimens were presented to the Western Australian Herbarium and Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) was recognised as being distinct. Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) has a highly restricted distribution limited to two populations on Yeelirrie Station, which is a pastoral lease located 72 km south of Wiluna in Western Australia. The larger of the two populations is situated near the boundary of Albion Downs Station (‘Area A’ in Clarke et al., 2012), while the smaller population is located c. 30 km to the northwest (‘Area B’ in Clarke et al., 2012). This species of saltbush is found only within a palaeovalley of the Yilgarn craton that contains significant near-surface uranium mineralisation that has potential for resource development (Clarke et al. 2012). The two populations – Area A and Area B show genetic differentiation and it is recommended they be managed as separate conservation units (Shepherd et al., submitted). In addition, although there is evidence of very limited gene flow between the two populations, the species appears to have limited dispersal potential because there is significant isolation-by-distance evident among subpopulations (separated by less than 5 km) of the Area A population (Clarke et al. 2012). In addition to the populations at Area A and Area B, a limited number of plants have naturally established on an old rehabilitation site on Yeelirrie Station. Western Botanical has undertaken regional surveys targeting six lake systems (Annean, Mason, Miranda, Nabberu, Noondie and Way) during late 2009 and early 2010 and undertook further surveys targeting seven lake systems in May 2010; however, no new populations of Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) were located. The regional surveys were focused on flora and vegetation communities of interest (including self-mulching clay depressions and clay flats within calcrete systems). Each lake system was assessed for species of conservation significance in areas that were first identified from a helicopter survey and then verified during on-ground vegetation mapping. Much of the area surveyed in each lake system was gypsum rather than calcrete and therefore did not support the same vegetation communities as Yeelirrie, even though pockets of the same species were observed. Although not specifically targeting Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025), a survey of calcrete vegetation within the Murchison endeavoured to investigate potential areas for the presence of the species. Eight calcrete areas were surveyed: Yeelirrie Station, Lake Way, Lake Mason, Lake Miranda, Lake Maitland, Lake Darlot, Cogla Downs / Yarrabubba / Pollele (this area contained calcrete between Lake Annean & Lake Mason) and Paroo Station (100 km west of Wiluna). No additional populations of Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) were found (Meissner, 2011). Relevant Biology/Ecology Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) is a recently discovered species which has been recorded from only two locations on Yeelirrie Station. A total of approximately 275,000 individuals are estimated for the two locations, comprising approximately 190,700 individuals at Area A and approximately 84,500 individuals at Area B (Western Botanical, 2011) (note: estimates for the number of female and male plants within each population are not available). The number of individuals was estimated using 10x10 m quadrats and floristic mapping. Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) (a saltbush) Conservation Advice Page 2 of 8 Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) is dioecious and the male and female reproductive organs are generally present on separate plants. As a consequence, population estimates must take into account the total number of female plants present, as this will impact the percentage of the population that may be able to produce seed. Atriplex, like other members of the family Chenopodiaceae, have small indistinct flowers and are wind pollinated. Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) also has separate male and female plants. These features strongly promote outcrossing, which would result in an increase in genetic diversity. However, the presence of some female fruits on male plants of Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) could indicate a level of self-fertilisation (i.e. inbreeding) is occurring. Many chenopods produce papery fruits and seeds that are often widely dispersed by wind or water. The fruits of Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) however, appear to be retained on old branches for long periods, possibly until branch death. Old grey fruits occur on the lower branches, while new fruits are maturing near the terminal branches. This is likely to limit the distance seeds are dispersed from maternal plants and in turn may limit gene flow across populations. Also, Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) appears to be restricted to a very specific habitat as it is apparently confined to self-mulching clays within one palaeo-channel. These old drainage channels are only approximately 30 km apart but it is unclear if the disjunct populations of Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) ever become interconnected during flood events. Overall the probability of gene dispersal between the two populations is likely to be low given the two populations show significant genetic differentiation based on both microsatellite (Clarke et al., 2012) and Amplified Fragment Length Polymorphisms (AFLPs) data (Shepherd et al., submitted). As Atriplex sp. Yeelirrie Station (L. Trotter & A. Douglas LCH 25025) is predominantly dioecious it is likely both a male and female plant would be required to establish any new population.