Cetrelia olivetorum (Nyl.) W. Culb. & C. Culb.

Praktlav

World distribution: Cetrelia olivetorum (in a wide sense, see note) is primarily a temperate species with a wide distribution. It is known from Europe, through Russia to southeast Asia, Alaska, and along the coast of eastern North America (W.L. Culberson & C.F. Culberson 1968, 1978, Golubkova 1981, Randlane & Saag 1991). Its main distribution in Europe covers the subatlantic areas in Central and South Europe, including the western parts of the British Isles (W.L. Culberson & C.F. Culberson 1968, Coppins 1976, Nimis 1993). In Sweden and Finland, the species is known from a few localities (Aronsson et al. 1995, Rassi et al. 1992)

Ecology: Results. The habitat was recorded at 60 localities: Quercus forest (2), Alnus incana forest (11), Betula woodland (16), Fagus forest (1), Populus stand (1), thermophilous deciduous forest (2), 'deciduous forest' (3), Picea forest (9), Pinus forest (6), mixed coniferous forest (3), unspecified forest (3), screes with forest (4), and meadows or grazing land (4). 13 habitats are recorded to be situated close to water, mainly running water (12), and 11 localities are within canyons or ravines. The substrate was indicated at 87 localities. The most common substrate was rocks or cliffs covered by mosses (56). The species was also recorded as an epiphyte (44) on Acer platanoides (1), A. pseudoplatanus (1), Alnus glutinosa (1), A. incana (2), Betula spp. (4), Fagus sylvatica (1), Juniperus communis (2), Picea abies (2), Pinus sylvestris (1), Populus tremula (1), Prunus padus (1), Quercus spp. (13), Salix caprea (2), Sorbus aucuparia (8), Tilia cordata (1), deciduous trees (1), on a fallen, corticated log of Betula sp. (1), and on a decaying log of Sorbus aucuparia (1). Discussion. Cetrelia olivetorum shows different substrate preferences in different parts of the distribution area: Along the southern and southwestern coast, it mainly grows on deciduous trees, especially Quercus spp.; along the western coast and especially in inland areas of southeastern Norway, it is mainly saxicolous on moss-covered boulders and cliffs. The preferred habitat is oak forests along the southern and southwestern coast, and boreal deciduous forests with cliffs or boulders further north on the west coast and in southeastern Norway. Forests containing Cetrelia olivetorum are often both well-lit and humid, and often influenced by previous grazing by domestic animals, especially in the northern part of the distribution area. In some regions, e.g. the upper valleys of southeastern Norway, this influence is probably important in most localities, and the species seems to have similar ecologically requirements as Flavoparmelia caperata, Heterodermia speciosa, and Menegazzia terebrata. Possible primary habitats are north-facing screes with open forest and canyons with spruce forest. Primeval forests may also have been primary habitats, as has been postulated for some other lichen species in the old agricultural landscape (S.G. Nilsson et al. 1994). Cetrelia olivetorum has in Norway and Sweden previously been reported as mainly growing on rock (Jørgensen & Ryvarden 1970, Aronsson et al. 1995). New localities, especially in Vest-Agder and Rogaland, show that it also is an important epiphyte, as it is in the British Isles (Purvis 1992b), Central Europe (Du Rietz 1924, Barkman 1958a, Wirth 1987), and southern Europe (Nimis 1993). It is mentioned as a species of old forests in Europe and North America (Wirth 1987, Rose 1992), while the occurrence on rock in old, grazed woodland, seems to be unique in Europe. In Great Britain it is primarily mentioned under the alliance 'Parmelion laevigatae', but also under 'Lobarion pulmonariae' (Seaward & Hitch 1982, James et al. 1977)

Threats: Results. Assumed threats were logging (36), overgrowth (14), construction (11), plantation of Picea abies (5), abrasion (4), pollution (2), development of hydroelectric power (1), expansion of existing road (1), and agricultural expansion (1). Discussion. The most serious threats against this lichen appear to be forestry (clear felling of deciduous forests and plantation of Picea abies) and change in the use of previously grazed forests, resulting in overgrowth. Logging is the main threat in our neighbouring countries (Rassi & Väisänen 1987, Aronsson et al. 1995). Pollution may be a threat along the south coast

Status: Thirty-one old localities were investigated; the species was found at 15, apparently extinct in 5, and of uncertain status in 11. Twenty-eight new localities were discovered. The following localities are within nature reserves: 773, 1195, 1790 (probably), 2098, and 3562

Notes: Following the taxonomy of W.L. Culberson & C.F. Culberson (1968), two species of Cetrelia occur in Norway (C. cetrarioides and C. olivetorum). These taxa are regarded as chemotypes of one species, C. olivetorum, by Norwegian authors (Jørgensen & Ryvarden 1970, Krog et al. 1994). Of the two chemotypes, the olivetoric acid chemotype is much more rare than the perlatolic chemotype..

Specimens in other herbaria, litterature, etc.