Allocetraria oakesiana (Tuck.) Randl. & Thell
Nomenclatural data
Basionym: Cetraria oakesiana Tuck., Bost. Journ. Nat. Hist., 3: 445. 1841. - Platysma oakesianum (Tuck.) Nyl., Memoir. Soc. Imp. Scienc. Natur. Cherbourg, 3: 172, 1855. - Tuckermannopsis oakesiana (Tuck.) Hale, Bryologist 90: 64, 1987. - Type: USA, New England, White Mountains,alpine regions, on the small braches of dwarf firs, Oakes, 25.06.1839 (FH, lectotype, selected here).
Cetraria oakesiana var. spinulosa Merrill, Bryologist 13: 25, 1910.
Cetraria bavarica Krempelh., Flora (Regensburg), 34: 273, 1851. - Type: Germany, Oberbayern, Krempelhuber, 06.1851 (UPS, isolectotype; seen).
Morphology
Thallus foliose to subfoliose, upper surface greenish yellow, lower surface brown to light tan, somewhat wrinkled, with sparse rhizines; lobes concave, moderately broad, c. 1 – 4 mm wide, weakly wrinkled, usually with abundant marginal soralia, soredia coloured of light yellow. Upper and lower cortex paraplectenchymatous but the hyphae are sometimes anticlinally arranged. Both cortical layers c. 20 µm, composed of c. 3 rather gelatinized cell layers each. Cells near the surfaces somewhat smaller than other cells. Medulla in many specimens yellowish in the lower parts.
Apothecia lateral, marginal to laminal, up to 6 mm in diameter, with brown disc and thin thalline margin which may turn sorediate.Exciple c. 80 µm thick. Asci narrowly clavate to cylindrical, 30–40 x 7–12 µm, tholus small, ocular chamber cylindrical and broad, axial body broad, 6–7 µm, ascospores globose, c. 5 x 5 µm. Pycnidia marginal, immersed to raised (globose or spinulose; the latter type of variation has been described by Merrill as var. spinulosa). Pycnidia pigmented or non-pigmented, sometimes with cortical tissue beneath, pycnoconidia 11–12 x 1 µm.
Chemistry
Usnic acid in the cortex; three fatty acids (caperatic, lichesterinic and protolichesterinic acids) and secalonic acids (+/-) in the medulla. Two unidentified fatty acids that were reported by Dey (1978) are evidently lichesterinic and protolichesterinic.
Remarks
Allocetraria oakesiana has usually been considered close to Tuckneraria laureri due to the similar thallus colour, sorediate margins and probably also distributon pattern. Later studies have shown that although the spores are subglobose in both taxa, the pycnoconidia are totally different (bifusiform in T. laureri) and several minor morphological and chemical differences occur (Randlane et al. 1994). A relationship between A. oakesiana and Tuckermannopsis chlorophylla was presumed by Kärnefelt et al. (1992). Further investigations of reproductive structures, however, show that these two species are not closely allied. They are somewhat similar morphologically but A. oakesiana differs in a broader axial body, filiform conidia and presence of usnic acid and seems in these important aspects to be a good member of Allocetraria. The cortex structure is also different. A. oakesiana is characterized by strongly gelatinized cortical cells with small lumina. This type of cortex is also found in e. g. Flavocetraria, Vulpicida and Cetraria kamczatica. However, in many taxa, the structure of the cortex seems to be a variable and uncertain character (Kärnefelt et al 1992, 1993, Randlane & Saag 1992, Mattsson & Lai 1992, Mattsson 1993). A. oakesiana is the only sorediate species within Allocetraria and with the distribution outside Southeast Asia - its main  area lies in Central Europe and North America.
Ecology and distribution
Allocetraria oakesiana differs from the other species in the genus in being distributed outside Southeast Asia. It is present in China (Wei 1991) but also in North America (Canada, USA) and Europe (Austria, Germany, Italy, Slovakia, Russia, Ukraine). It is corticolous on coniferous and deciduous trees in montane forests.
Literature:
Randlane, T. & Saag, A. 1993. | Randlane, T. & Saag, A. 2004. | Randlane, T., Saag, A. & Obermayer, W. 2001. | Randlane, T., Saag, A. & Thell, A. 1997. | Thell, A., Randlane, T., Kärnefelt, I., Gao, X. & Saag, A. 1995.
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