This Conservation Advice was approved by the Minister / Delegate of the Minister on: 1/10/2008 Approved Conservation Advice (s266B of the Environment Protection and Biodiversity Conservation Act 1999) Approved Conservation Advice for Muehlenbeckia horrida subsp. abdita (Remote Thorny Lignum)
This Conservation Advice has been developed based on the best available information at the time this Conservation Advice was approved; this includes existing plans, records or management prescriptions for this species.
Following taxonomic revision, the name of this species has changed, and is listed under the EPBC Act as Duma horrida subsp. abdita as at 31 October 2015.
Description Muehlenbeckia horrida subsp. abdita, Family Polygonaceae, also known as Remote Thorny Lignum, is a divaricately to intricately branched, spreading erect shrub that grows to a height of 0.6–1.2 m. Flowers are rare, appearing only after plants are inundated, and form in bright, light-yellow clusters with 5 perianth segments. Muehlenbeckia horrida subsp. abdita has fewer perianths, no warty protuberances, a more divaricate and intricate branching habit, fewer leaves at flowering and a less erect habit than M. horrida subsp. horrida (Wilson, 1996).
Conservation Status Remote Thorny Lignum is listed as critically endangered. This species is eligible for listing as critically endangered under the Environment Protection and Biodiversity Conservation Act 1999 (Cwlth) (EPBC Act) as in 2006, the Minister considered the Threatened Species Scientific Committee's (TSSC) advice under section 189 of the EPBC Act and amended the list under section 184 to include Remote Thorny Lignum. The TSSC determined that this species met criteria 1, 2, 3 and 4 of their eligibility criteria (TSSC, 2006b). The species is also listed as rare or likely to be become extinct under the Wildlife Conservation Act 1950 (Western Australia).
Distribution and Habitat Remote Thorny Lignum is endemic to Western Australia and is restricted to three lakes south of Newdgate, 360 km south-east of Perth. The species is found on clay and silt depressions in seasonally inundated freshwater wetlands. Inundation may not occur in the wetlands for several years and the species can survive inundation for up to 12 months. The total population size is 2000 individuals, all occurring within the Lake Bryde Nature Reserve; 45 000 dead individuals were discovered in an overly saline area in June 2000 (Phillimore et al., 2003). The species’ extent of occurrence is 7.5 km2 and its total area of occupancy is 1.28 km2 (TSSC, 2006a). Species associated with Remote Thorny Lignum include Tecticornia verrucosa on lake beds with Melaleuca strobophylla and Eucalyptus occidentalis in open woodland fringing the lakes. This species occurs within the Avon (Western Australia) Natural Resource Management Region. The distribution of this species is not known to overlap with any EPBC Act-listed threatened ecological communities.
Muehlenbeckia horrida subsp. abdita Conservation Advice - Page 1 of 3 This Conservation Advice was approved by the Minister / Delegate of the Minister on: 1/10/2008 Threats The main identified threats to Remote Thorny Lignum include recreational activities and disrupted hydrology resulting in increased salinity and waterlogging; and an absence of periodic flooding and drying, resulting in a lack of recruitment (TSSC, 2006a).
Research Priorities Research priorities that would inform future regional and local priority actions include: • Design and implement a monitoring program or, if appropriate, support and enhance existing programs. • More precisely assess population size, distribution, ecological requirements, soil seed bank dynamics, pollination biology, response to fire, population genetics and the relative impacts of threatening processes. • Undertake survey work in suitable habitat and potential habitat to locate any additional populations/occurrences/remnants. • Undertake seed germination and vegetative propagation trials to determine the requirements for successful establishment.
Regional and Local Priority Actions The following priority recovery and threat abatement actions can be done to support the recovery of Remote Thorny Lignum. Habitat Loss, Disturbance and Modification • Monitor known populations to identify key threats. • Monitor the progress of recovery, including the effectiveness of management actions and the need to adapt them if necessary. • Manage threats to areas of vegetation that contain populations/occurrences/remnants of Remote Thorny Lignum. • Investigate options for revegetating areas surrounding lakes to lower the water table. • Manage any changes to hydrology that may result in changes to the water table levels, increased waterlogging and salinity. • Control access routes to suitably constrain public access to known sites on public land. • Suitably constrain recreational use of the lakes that may adversely impact known populations. • If additional populations are located, investigate further formal conservation arrangements such as the use of covenants, conservation agreements or inclusion in reserve tenure. Conservation Information • Raise awareness of Remote Thorny Lignum within the local community, particularly water-skiers and neighbouring landholders. Enable Recovery of Additional Sites and/or Populations • Undertake appropriate seed collection and storage. • Investigate options for linking, enhancing or establishing additional populations. • Implement national translocation protocols (Vallee et al., 2004) if establishing additional populations is considered necessary and feasible.
This list does not necessarily encompass all actions that may be of benefit to Remote Thorny Lignum, but highlights those that are considered to be of highest priority at the time of preparing the conservation advice.
Muehlenbeckia horrida subsp. abdita Conservation Advice - Page 2 of 3 This Conservation Advice was approved by the Minister / Delegate of the Minister on: 1/10/2008 Existing Plans/Management Prescriptions that are Relevant to the Species • Remote Thorny Lignum (Muehlenbeckia horrida subsp. abdita) Interim Recovery Plan 2003–2008 (Phillimore et al., 2003), and • Unwooded freshwater wetlands of the southern Wheatbelt of Western Australia, dominated by Muehlenbeckia horrida subspecies abdita and Tecticornia verrucosa across the lake floor (Hamilton-Brown & Blyth, 1999). These prescriptions were current at the time of publishing; please refer to the relevant agency’s website for any updated versions.
Information Sources: Hamilton-Brown, S & Blyth, J 1999, Unwooded fresh water wetlands of the southern Wheatbelt of Western Australia, dominated by Muehlenbeckia horrida subspecies abdita and Tecticornia verrucosa across the lake floor, Interim Recovery Plan #48, Department of Conservation and Land Management, Western Australia. Phillimore, R, Giraudo, M & Brown, A 2003, Remote Thorny Lignum (Muehlenbeckia horrida subsp. abdita) Interim Recovery Plan 2003-2008, Department of Conservation and Land Management, Western Australian Threatened Species and Communities Unit, viewed 14 April 2008,
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