Axenic cultures of lichen photobionts isolated from bark-inhabiting
lichen thalli of the Physcietum adscendentis
Ochsner were identified by light microscopy and sequence comparisons
of internal transcribed spacer rDNAs to
investigate principles of lichenization within a defined lichen
sociological unit. The photobiont identity of eight
lichen species is reported for the first time (photobiont species in square
brackets): Lecania cyrtella (Ach.) Th. Fr.
[Trebouxia arboricola Puym.], Lecania naegelii
(Hepp) Diederich & v. d. Boom [Dictyochloropsis symbiontica
Tscherm.-Woess], Candelaria concolor (Dicks) B. Stein
[Trebouxia jamesii (Hildreth & Ahmadjian) Gärtner],
Candelariella cf. reflexa (Nyl.) Lettau
[T. jamesii], Lecanora spec.
[T. arboricola], Phaeophyscia orbicularis (Neck.)
Moberg [T. impressa Ahmadjian], Physcia
adscendens (Fr.) H. Olivier [T. impressa] and
Lecidella elaeochroma
(Ach.) M. Choisy [T. arboricola] and could be
confirmed for another two species, Physcia stellaris (L.) Nyl.
[Trebouxia impressa] and Xanthoria parietina
(L.) Th. Fr. [Trebouxia arboricola]. The observation
that pioneer
lichens without vegetative propagules, growing on smooth bark,
had Trebouxia arboricola as photobiont can be
explained by the assumption of a free-living population of
Trebouxia arboricola. Species of photobionts from
Xanthoria parietina were morphologically and genetically different
from
those of Physcia adscendens and
Phaeophyscia orbicularis, respectively; a finding that does not
support the previous assumption that Xanthoria
parietina takes over its algal partner from a Physcia
species, at least at the sites investigated.