Physconia subpallida occurs in severely fragmented locations throughout eastern North America. Its Extent of Occurrence, Area of Occupancy, and extant and quality of its habitat have declined substantially over the past century due to widespread logging, air pollution, and development. Now, there are fewer than 2,500 individuals left (total population size estimated at 400 mature individuals) after substantial declines, and most subpopulations are very small, consisting of 1-5 individuals, with the largest subpopulation consisting of fewer that 250 mature individuals. The habitat for this species is now very limited throughout its range as it appears to require old-growth deciduous forests, which are rare and fragmented throughout its core range in south-eastern Ontario (Henry & Quinby 2010, McMullin2015, McMullin et al. 2016, Allen & McMullin 2019). The total Area of Occupancy [AOO] is estimated to be very small, with the known AOO only 260 km2, up to a potential maximum of 324 km2. Therefore,this species is Endangered, B2ab(i,ii,iii,iv,v); C2a(i).
Assessor/s: McMullin, T., Allen, J. & Lendemer, J.; Reviewer/s: Stone, D.; Facilitator(s) and Compiler(s): Bishop, G. & Allen, J.
Allen, J.L. & McMullin, R.T. (2019) Modeling algorithm influence o n the success of predicting newpopulations of rare species: Ground - proofing models for the Pale - Belly Frost Lichen (Physconia subpallida) in Ontario. Biodiversity and Conservation28: 1853-1862.