188
E. IMRE FRIEDMANN AND MARGALITH GALUN
arid regions. This region is completely lacking in phanerogamic plants and
is designated by the authors as a fog-induced "lichen oasis," the only
source of moisture apparently being clouds or fog moving over the area.
On open clay-soil depressions, the same authors also found Buellia auriculata Malme, Solenopsora requienii Mass., Acarospora chilensis Magn.,
Caloplaca cirrochroa (Ach.) Th. Fr., and fragments of Collema and
Ramalina species.
Weber (1962) claims that despite the slow growth of the crustose lichens,
the dominating growth form in arid regions, the lichen floras encountered
in arid sites are unusually rich in species belonging to the desert-steppe,
circumboreal, and subtropical elements. In his opinion, this phenomenon
arises from local peculiarities in topography and exposure, which result
in the coexistence of arid and mesic elements in relatively small areas.
Faurel et al. (1953) made a data compilation (Bouly de Lesdain, 1911;
FJagey, 1896; Hue, 1921; Maire, 1933; Nylander, 1878; Steiner, 1902*;
Tits, 1925; Werner, 1950) on lichens of the Sahara. Taking also into account their own collections, they recorded 114 lichen species, as compared
with 1000 phanerogams, in the Algerian Sahara and Tibesti region. None
of the 114 species belong to the fruticose growth form, and only three are
foliose; all the rest are crustose types. Of the latter, 20% are Pyrenolichenes, 28% belong to the Cyanophilia and 13% to the Acarosporaceae.
Similar proportions are apparent in the composition of other desert lichen
floras: Dermatocarpon and Heppia are represented by 23 species, 20%
of the components of the Sahara lichens so far reported. This is a surprisingly large amount considering that these two genera are less than 1%
of the total global lichen flora.
In a more recent publication, Faurel and Schotter (1958) added 17
species to the list of lichens identified in Tibesti. An abundance of
Acarospora species (A. bella, A. sulphurata, A. pitardi, A. strigata, A.
cf. versicolor, A. cf. intermixta, A. cf. veronensis) as well as of individuals
of these species in Tibesti has been reported by Quézel. Many of these
Acarosporas are deteriorated by the blue-green alga Stigonema minutissimum f. lichenicolum, which settles in the thallus and fruiting-body
depressions.
A rather rich lichen flora, both as regards the number of species and
the abundance of individuals has been found in the Negev Desert of Israel,
a region 9000 km
2
in area (Galun and Reichert, 1960; Galun, 1966,
1967). Of the 44 species reported, Ramalina maciformis (Del.) Bory and
Teloschistes lacunosa (Rupr.) Sav. [ = T. brevior (Nyl.) Wain. f.
halophilus (Elenk.) Oxn.] are the only fruticose lichens in this area. The
* There was also an earlier report on Sahara lichens by Steiner (1895).
E. IMRE FRIEDMANN AND MARGALITH GALUN
arid regions. This region is completely lacking in phanerogamic plants and
is designated by the authors as a fog-induced "lichen oasis," the only
source of moisture apparently being clouds or fog moving over the area.
On open clay-soil depressions, the same authors also found Buellia auriculata Malme, Solenopsora requienii Mass., Acarospora chilensis Magn.,
Caloplaca cirrochroa (Ach.) Th. Fr., and fragments of Collema and
Ramalina species.
Weber (1962) claims that despite the slow growth of the crustose lichens,
the dominating growth form in arid regions, the lichen floras encountered
in arid sites are unusually rich in species belonging to the desert-steppe,
circumboreal, and subtropical elements. In his opinion, this phenomenon
arises from local peculiarities in topography and exposure, which result
in the coexistence of arid and mesic elements in relatively small areas.
Faurel et al. (1953) made a data compilation (Bouly de Lesdain, 1911;
FJagey, 1896; Hue, 1921; Maire, 1933; Nylander, 1878; Steiner, 1902*;
Tits, 1925; Werner, 1950) on lichens of the Sahara. Taking also into account their own collections, they recorded 114 lichen species, as compared
with 1000 phanerogams, in the Algerian Sahara and Tibesti region. None
of the 114 species belong to the fruticose growth form, and only three are
foliose; all the rest are crustose types. Of the latter, 20% are Pyrenolichenes, 28% belong to the Cyanophilia and 13% to the Acarosporaceae.
Similar proportions are apparent in the composition of other desert lichen
floras: Dermatocarpon and Heppia are represented by 23 species, 20%
of the components of the Sahara lichens so far reported. This is a surprisingly large amount considering that these two genera are less than 1%
of the total global lichen flora.
In a more recent publication, Faurel and Schotter (1958) added 17
species to the list of lichens identified in Tibesti. An abundance of
Acarospora species (A. bella, A. sulphurata, A. pitardi, A. strigata, A.
cf. versicolor, A. cf. intermixta, A. cf. veronensis) as well as of individuals
of these species in Tibesti has been reported by Quézel. Many of these
Acarosporas are deteriorated by the blue-green alga Stigonema minutissimum f. lichenicolum, which settles in the thallus and fruiting-body
depressions.
A rather rich lichen flora, both as regards the number of species and
the abundance of individuals has been found in the Negev Desert of Israel,
a region 9000 km
2
in area (Galun and Reichert, 1960; Galun, 1966,
1967). Of the 44 species reported, Ramalina maciformis (Del.) Bory and
Teloschistes lacunosa (Rupr.) Sav. [ = T. brevior (Nyl.) Wain. f.
halophilus (Elenk.) Oxn.] are the only fruticose lichens in this area. The
* There was also an earlier report on Sahara lichens by Steiner (1895).