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Recovery Strategy for the Western Spiderwort (Tradescantia occidentalis) in Canada – 2013

Executive Summary

  • Western Spiderwort is a perennial monocot with three-petaled purple flowers, grass-like foliage, and seeds in capsules. In Canada, it is associated with semi-arid sand dune complexes in all three Prairie Provinces. Currently there are four confirmed populations in Canada with two in Manitoba, one in Saskatchewan and one in Alberta. As of 2010, the Canadian population was estimated to be over 100,000 plants on 39 quarter sections with an index area of occupancy of 76 km2. Western Spiderwort was listed as Threatened under the Species at Risk Act in 2005.

  • Any additional loss of habitat among the known populations of Western Spiderwort would adversely affect the species' survival in Canada. Threats to Western Spiderwort are not the same across the range, but rather more pervasive in some populations than others. Current or potential future identified threats to Western Spiderwort include invasive alien species, alteration to, or suppression of, grazing and/or fire regimes, prolonged wet climactic period, incidental mortality from overgrazing by wildlife and domestic livestock, cultivation, sand and gravel extraction, road maintenance and construction, oil and gas activities and recreational activities.

  • Recovery of Western Spiderwort is deemed biologically and technically feasible. The population and distribution objectives are to maintain and, if possible, increase the current estimated distribution of the existing naturally occurring populations and to similarly maintain and, if possible, increase the distribution of any newly-discovered naturally occurring populations. Specifically for each of the four existing populations the population and distribution objectives are to maintain mature individuals in at least 6 quarter sections of the Lauder Sand Hills in MB, 7 quarter sections of the Routledge Sand Hills in MB, 18 quarter sections of the Elbow Sand Hills in SK, and 8 quarter sections of the Pakowki Sand Hills in AB. Broad strategies to be taken to address the threats to the survival and recovery of Western Spiderwort are presented in the section on Strategic Direction for Recovery.

  • Critical habitat is identified for all known naturally occurring Western Spiderwort populations in Canada. The primary habitat needed by Western Spiderwort consists of moderately sloped, partially stabilized sand dunes with patches of bare sand, as well as more stabilized dune slacks, rolling sand hills and grasslands. Critical habitat consists of all known occupied primary habitat patches, plus all natural landforms, soil and native vegetation within 300 m of the habitat patch.

  • One or more action plans for Western Spiderwort will be completed by 2017.