Conservation Advice Pimelea Spinescens Subsp

THREATENED SPECIES SCIENTIFIC COMMITTEE Established under the Environment Protection and Biodiversity Conservation Act 1999 The Minister’s delegate approved this Conservation Advice on 16/12/2016. Conservation Advice Pimelea spinescens subsp. spinescens spiny rice-flower Conservation Status Pimelea spinescens subsp. spinescens (spiny rice-flower) is listed as Critically Endangered under the Environment Protection and Biodiversity Conservation Act 1999 (Cwlth) (EPBC Act) effective from 1 May 2003. In Victoria it is listed as Endangered under the Advisory List of Rare or Threatened Plants in Victoria 2014 , and Threatened under the Victorian Flora and Fauna Guarantee Act 1988. The main factor that is the cause of the species being eligible for listing in the Critically Endangered category is a very restricted area of occupancy that is likely to continue to decline due to clearing for land development, habitat degradation due to invasive weeds, land management practices and lack of successful recruitment under these and projected future drier conditions. Description Spiny rice-flower is a small spreading shrub growing to 50 cm in height. It has narrow, green, hairless, oval leaves 2 – 10 mm long and 1 – 3 mm wide, and older stems are often spine-tipped. Clusters of between 6 and 12 small, unisexual (rarely bisexual), hairless pale yellow flowers form the inflorescences. Flowers are 1.5 – 3 mm long (males slightly larger than females) and have four ovate petal-like lobes. Floral clusters are subtended by four leaf-like bracts 3 – 7 mm long and 1.5 – 4 mm wide. Fruits are ovoid, approximately 3 mm long, 1-seeded, with a thin fleshy layer surrounding the oily seed (description from Walsh & Entwisle 1996). Plants from more northerly populations appear more robust than those from southern areas. Hairless flowers and stalks separate this subspecies from Pimelea spinescens subsp. pubiflora (Wimmera rice-flower) (Carter & Walsh 2006). Distribution Spiny rice-flower is endemic to Victoria, where it occurs in the central west of the state (Walsh & Entwisle 1996); predominantly in the Victorian Volcanic Plain, Victorian Midlands and Riverina IBRA (Interim Biogeographic Regionalisation for Australia) Bioregions (DEH 2000). Based on entries in the spiny rice-flower state-wide database, approximately 88 000 plants are estimated to occur in 208 (and possibly up to 275) wild sites (Foreman 2012). Historically, the species was undoubtedly much more widespread and abundant within the region where it currently occurs (Carter & Walsh 2006). Populations are now substantially fragmented and depleted due to land clearance for settlement, industry and agriculture. Many populations consist of a small number of plants (55 percent of sites with population counts have fewer than 100 plants), with most occurring in tiny patches of remnant habitat (59 percent of sites with extent estimates are smaller than 1ha) such as on roadsides and rail easements (Carter & Walsh 2006). However, the spiny rice-flower database includes many old and imprecise records and these figures are likely to be an overestimate of the actual situation. Some large populations occur on private property where grazing impacts are light (Recovery Team pers. comm., 2016). Pimelea spinescens subsp. spinescens (spiny rice-flower) Conservation Advice Page 1 of 8 Life history The spiny rice-flower is slow-growing and may live up to 100 years (Mueck 2000). Most plants have either female or male flowers, but some have both or predominantly bisexual flowers (Foreman 2012; Reynolds 2013). Recruitment was previously thought to be low, with germination or seedling survival an irregular event (Mueck 2000) and most populations appearing to consist of relatively mature plants with little evidence of recruitment (Mueck 2000). However, since 2006 targeted monitoring (Cropper 2003, 2009; Foreman 2005, 2011) and research (Reynolds 2013) has found germination and recruitment to be widespread. A recruitment level (i.e. germinants surviving the first summer) of 14 percent was reported from sites within the Volcanic Plains (Reynolds 2013), which was likely associated with optimal climatic conditions (Foreman 2012). Recruitment dynamics and requirements for successful in situ recruitment and persistence are not well understood (Foreman 2012), as not all seed will germinate even if conditions are optimal (Reynolds 2013). However, like most grassland species, the species is tolerant of fire and mature plants readily resprout after fire (Mueck 2000). The species flowers from April to August (Entwisle 1996) and germinates from July to November (Foreman 2011; Reynolds 2013). Germination appears to be regulated partly by rainfall, with autumn drought and high rainfall both apparently preventing germination (Foreman 2011; Foreman 2012). Germinants are often found in areas close to female or bisexual plants, suggesting that dispersal distances are small (Foreman 2011). Genetic analysis of seed showed that most seed results from outcrossing via pollinators (James & Jordan 2014) but some seed appeared to result from selfing, indicating that there is a degree of self-compatibility in the breeding system. Mixed mating systems are common in plant species but outcrossing generally provides a greater level of genetic diversity, which is the basis for adaptation and should be a high priority for management. Habitat Spiny rice-flower is predominantly associated with two threatened ecological communities: ° ‘Natural Temperate Grassland of the Victorian Volcanic Plain’ – listed as Critically Endangered under the EPBC Act (TSSC 2008). This community is also listed under the Flora and Fauna Guarantee Act 1988 (Vic) (FFG Act) as ‘Western (Basalt) Plains Grasslands’; and ° ‘Natural Grasslands of the Murray Valley Plains’ – listed as Critically Endangered under the EPBC Act (TSSC 2012), and listed as ‘Northern Plains Grasslands’ under the FFG Act (DSE 2003). Spiny rice-flower has also been reported in association with Eucalyptus leucoxylon (yellow gum) and E. microcarpa (grey box) grassy woodland in the Goldfields (Foreman 2005), and Allocasuarina luehmannii (Buloke) open grassy woodland in the Wimmera (Deanna Marshall pers. comm., cited in Foreman 2012). It is likely these grassy woodland habitats represent ecological communities also listed under the EPBC Act. The species occurs in grassland or open shrubland, usually developed on clay soils (Walsh & Entwisle 1996). Plants from more northerly populations occur on red clay complexes, while plants from southern populations occur on heavy grey-black clay loams derived from basalt. Topography is generally flat but populations may occur on slight rises or in slight depressions prone to temporary inundation. Vegetation is often dominated by Themeda triandra (kangaroo grass), with Austrostipa spp. (speargrass) or Rytidosperma spp. (wallaby grass) commonly associated. Co-occurring species often include Acaena echinata (sheep’s burr), Calocephalus citreus (lemon beauty-heads), Chrysocephalum apiculatum (common everlasting), Eryngium ovinum (blue devil), Plantago varia (variable plantain), Ptilotus erubescens (hairy tails), Pimelea spinescens subsp. spinescens (spiny rice-flower) Conservation Advice Page 2 of 8 Schoenus apogon (common bog-sedge) and Velleia paradoxa (spur velleia) (Carter & Walsh 2006) . Threats The primary threats to spiny rice-flower are land clearing and habitat degradation. Most of the populations are small and fragmented, and their long-term viability is doubtful without intensive site management. Reduced connectivity limits gene-flow between sites, and genetic integrity is at risk if inbreeding ocurrs as a result of distances between sites being greater than the travel distance of pollinators. Large populations can also experience significant declines over relatively short periods of time, especially following periods of drought (Foreman 2012). Table 1 – Threats to the spiny rice-flower in approximate order of severity of risk, based on available evidence. Threat Threat type and status Evidence base factor Habitat loss and fragmentation Changing known current Several very large populations occur on private land use - property potentially subject to changing land pasture use, such as from grazing to cropping, or from improvement farming to industrial and residential uses, that and could severely damage or destroy populations agricultural (Carter & Walsh 2006). Although this threat is intensification uneven across the species’ range, it remains a high risk where tenure is unsecured (Foreman 2012). Road and rail known current Many populations occur along roadsides and maintenance some rail reserves, and are at great risk from any maintenance works such as slashing, grading, clearing, herbicide application, widening and soil compaction by vehicle movement (Carter & Walsh 2006). Fire Prolonged known current Fire creates inter-tussock spaces which reduces lack of fire the abundance of annual exotic grasses, which can otherwise crowd out the spiny rice-flower (Foreman 2012). In the southern populations, it has been observed that the absence of disturbance from fire results in a rapid decline or cessation in recruitment, and population extirpation if sustained (Foreman 2012). The same process applies in the north, but at a slower rate, suggesting that controlled grazing can mimic some of the positive effects of fire (Foreman 2012). Pimelea spinescens subsp. spinescens (spiny rice-flower) Conservation Advice Page 3 of 8 Invasive plants Weed known current Habitat degradation

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