The Rediscovery and Distribution of Rumex drummondii (Polygonaceae) in South-Western Australia

Abstract

Rumex drummondii Meisn., a south-western Australian endemic vascular plant species recorded from widely separated localities, had not been collected for 46 years and was considered possibly extinct. The methods developed from search theory, which has been used for finding lost people or objects, were applied to finding R. drummondii, starting from previous records. Eleven populations of the species were discovered within a 50 km radius in the Kalgan River and Manypeaks region. A disjunct population of six plants was found in 1992 in a parking area at a crossing of the Moore River, 480 km north north west of the others, but had disappeared by 1994. Surveys in the Gingin Brook and Moore River region and between Kalannie and Kulja, another disjunct record, failed to find further plants. The species occupies temporarily wet depressions, lake edges and roadside excavations and dam edges protected from grazing by sheep; habitats also occupied by congeneric weedy species. The species occurs on road verges and farmland and is known from one nature reserve. The rediscovery of R. drummondii enables it to be included in the assessment of potential biological control agents for related weed species in the genera Emex and Rumex.