World distribution: Physcia semipinnata occurs in Europe, North America, and Asia (India) (Coppins 1992b). In Europe it is a southern species, being most common in the Mediterranean region (Nimis 1993). The species is decreasing in the British Isles (Coppins 1992b). In Fennoscandia it is a southern species with coastal affinities, occurring in Norway, Sweden, Denmark, and, very sparsely in Finland (Moberg 1977)
Ecology: Results. The substrate (indicated in 9 localities) included Fraxinus excelsior (trunks and branches; 2), Acer pseudoplatanus, Fagus sylvatica, Malus domestica, Populus tremula (top branches), Prunus avium, Sambucus sp., and Salix sp. (all 1). Recorded habitats (8 localities) included old gardens (3), avenues of deciduous trees (2), maritime sites (2), broad-leaved deciduous forests (2), and a Populus tremula grove in a pasture (1). Discussion. Physcia semipinnata is a species of eutrophic bark of various deciduous trees in habitats influenced by man. The many occurrences of the species on solitary trees indicate a preference for well-lit habitats, often near the sea. In the British Isles it occurs mostly on shrubs and tree branches, rarely on rocks (Coppins 1992b)
Threats: Results. Recorded threats include building on the site (1951, 1095) and logging and planting of Picea (1945). In one site (3757) the tree on which Physcia semipinnata was collected was felled in 1993. Discussion. Random extinction is a general threat to species occurring with small and few populations
Status: Seven old localities were investigated. The species was present in 3 and regarded as uncertain in 4. One new locality was found. There are no protected localities
Specimens in O: