Description of four new species of limestone associated Torresitrachia land snails (Mollusca: Pulmonata: Camaenidae) from the Katherine District of the Northern Territory, with comments on their conservation
Four new species of land snails of the genus Torresitrachia (Pulmonata: Camaenidae) are described from the Northern Territory of Australia: T. darwini, T. wallacei, T. cuttacutta, T. alenae. The species are distinguished on the basis of differences in shell and animal morphology, and 16S DNA analysis. All four species occur in the Katherine District (Daly Basin Bioregion), and have remarkably small geographical ranges and fragmented populations. Though not all species of Torresitrachia are associates of limestone, these four species are obligately associated with limestone outcrops supporting monsoon/deciduous vine thicket vegetation. Annual grasses, which are replacing the natural vegetation, do not offer suitable habitat for these land snails and they are much more prone to the ‘grass/fire cycle’, thus threatening the snails’ long term survival. Presently all the known populations of two of these new snails, T. wallacei and T. alenae, appear to be under threat of extinction and none occurs within any reserve.