The distribution, habitat requirements and conservation status of the plains rat, Pseudomys australis (Rodentia : Muridae)

Abstract

Species in the Pseudomys australis complex were historically widely distributed in a variety of habitats over southern Australia. By 1990 the group had apparently declined to a single species in the centre of its former range in the north-western Lake Eyre Basin, in gibber plain areas. In the past, the species has been collected only after exceptional annual rainfall. This study sought to define the current distribution of P. australis and to determine its preferred habitats during the usual prolonged dry periods. Allozyme electrophoresis on blood and tissue samples were used to investigate the genetic distinctiveness of geographically separated populations. The known distribution has been extended along a belt of gibber habitats running from north-west of Lake Eyre on the Northern Territory border to south of Lake Eyre South, and a discrete population inhabiting gibber tableland west of Lake Torrens. Pseudomys australis was extant in low-lying patches of deep cracking clay associated with minor drainage features and small depressions of cracking clay ‘gilgai’ common on some gibber plains. The former type sustained significantly denser populations, which we suggest represent ‘source’ habitats or ‘refugia’ during droughts. Many of the 16 localities at which the species was recorded are geographically separated; however, electrophoretic analyses showed high levels of allozyme heterozygosity and no evidence of speciation.