DistributionRead full entry
Distribution and Habitat
The distribution of Geocrinia alba is extremely restricted, fragmented, and contained within an area north and west of the Blackwood River between Margaret River and Augusta, extreme s.w. WA (Roberts et al. 1999). The extent of occurrence of the species is approximately 130 km2 and the area of occupancy is less than 2.5 km2 (Roberts et al. 1999). Most populations are small, with 48 of the 61 known extant populations numbering 50 individuals or less (Driscoll 1999). Long term population monitoring data, based on calling males, is available for three populations from the period 1992-1997. Populations varied in size over this period (Roberts et al. 1999) with a maximum of 121 calling males captured in 1994 at Forest Grove (Driscoll 1998). Based on current evidence, the best estimate of total adult population size for this species is twice the estimated number of males (Driscoll 1998).
Geocrinia alba is known from Leeuwin-Naturaliste NP and Forest Grove and Witchcliffe SF (Tyler 1997). Most of the species range occurs on privately owned land (Roberts et al. 1999).
Wardell-Johnson and Roberts (1993) described the biogeographic barriers separating the distributions of four allopatric species from the Geocrinia rosea complex. Both G. alba and G. vitellina 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 (Wardell-Johnson & Roberts 1993). Geocrinia alba is restricted to broad U shaped drainage depressions with swampy floors within undulating to hilly country on Leeuwin Block granite and narrow V shaped valleys on laterized Perth Basin sediments (Wardell-Johnson & Roberts 1991).