The distribution of the four allopatric species of the Geocrinia rosea (Harrison, 1927) complex in south-western Australia is described in relation to climate, landform and soils. A total of 221 positive distribution records for the complex are correlated with climatic profiles generated by the computer program BIOCLIM. No additional sites were predicted for the complex, but each of the sixteen climatic variables examined were influential in separating the distributions of the four species. Two rare species, G. alba (Wardell-Johnson & Roberts, 1989), which occupies 190 ha over a range of 101 km2, and G. vitellina (Wardell-Johnson & Roberts, 1989), 20 ha over 6.3 km2, occur in permanently moist sites in relatively dry and seasonal climatic zones and their distributions are separated by 9 km of lateritic uplands and narrow valleys. The range limits of two more widespread and common species; G. rosea and G. lutea (Main, 1963), are separated by 39 km of broad swampy terrain that is dry in summer. These two species pairs are separated by 47 km of muted topography which includes lateritic uplands, broad swampy terrain and narrow stream channels in a relatively dry climatic envelope. All calling sites of the complex examined, (fifteen), were on slopes in sandy alluvial soils with a high organic content. Narrower more subtle geographic barriers than previously envisaged may have allowed in situ speciation in the frog fauna in south-western Australia.