Ramalina arsenii Serusiaux, van den Boom & Magain

Ramalina arsenii Sérusiaux, van den Boom & Magain; Mycobank #840281 The Lichenologist 53(6): 434 (2021). Type: ― Switzerland, Valais canton, Saastal, near Saas-Grund, slightly calcareous rocks at edge of coniferous forest, 1680 m, 46°08.13′ N, 007°56.19′ E, August 2018, E. Sérusiaux s. n. (LG DNA 6389) (G— holotype; LG— isotype) (Sérusiaux et al. 2021). Thallus fruticose, saxicolous, light yellow-green to green, consisting of cushions of upright lobes divided dichotomously. Lobes typically 1 to 2.5 cm long. Soralia present, initially formed on lobe margins, then expanding at undersides or along lateral branches, in some thalli, small branches lack soralia but develop delicate phyllidioid or isidioid, flattened lobules. The apex of the old lobes may resemble a helmet. Isidia absent. Pseudocyphellae present, forming longitudinal lines along short branchlets, infrequently opening with tiny callus lines. Apothecia very rare, not seen. Chemistry: Medulla spot tests K–, C–, KC–, PD–, UV–; TLC: Evernic acid in the medulla and usnic acid in the cortex (Sérusiaux et al. 2021). Ecology and distribution: Ramalina arsenii is newly documented for Iran. It occurs both at low and high elevations. This species is known elsewhere from montane regions of Southwestern Europe, including France, SW Germany, Spain and Switzerland. Its distinct ecological niche on perpendicular calcareous rocks facilitates its identification (Sérusiaux et al. 2021). Notes: Ramalina arsenii and the similar R. europaea belong to the R. pollinaria group, which has been revised recently using ITS sequencing (Garparyan et al. 2017, Sérusiaux et al. 2021). This revealed that the since long accepted R. pollinaria consisted of 4 very similar species. One species, R. labiosorediata Gasparyan et al. (2017), occurs in North America, the other three are sympatric in Europe and surroundings, and their distinction on morphological grounds needs great care. In case of doubt, ITS sequencing is recommendable. Both specimens from Iran are found on rock and match the description of R. arsenii. This resembles most closely R. europaea, from which it was distinguished by differences in the ITS sequence (Sérusiaux et al. 2021). Morphologically both species are very similar, with 1–3 cm long lobes and sometimes spine-like proliferations with punctiform soralia on the top. Sérusiax et al. (2021) present the presence of ovoid excavate depressions on the thallus surface as distinguishing character for R. europaea. The reported substrates suggest a slight difference in ecological preferences, because R. europaea is reported from trunks and calcareous and siliceous rock, while R. arsenii is known only from calcareous rock. R. arsenii also resembles the exclusively North American species R. labiosorediata and they share the development of soralia mainly on the undersurface of the lobe tips. Ramalina arsenii is exclusively found on overhangs of calcareous rock formations, while R. labiosorediata is primarily found on trees and occasionally documented from rock. R. carminae R. Arroyo & Seriñá is another similar species growing on rock overhangs and can be differentiated from R. arsenii by producing variolaric acid instead of evernic acid and by the palmately branched lobe tips (Sérusiaux et al. 2021). Specimens examined: EAST AZERBAIJAN PROVINCE: Kalibar, ca. 4 km from Kalibar town, Galadarasi, toward Babak Castle, Arasbaran forest, 38.864789N, 46.968889E, 1750–2000 m, 19 August 2005, M. Sohrabi 4703 (ICH). MAZANDARAN PROVINCE: Behshahr, ca. 15 km from Behshahr town, Abbass-abbad forests, 36.664541N, 53.598829E, 400–600 m, 20 May 2004, M. Sohrabi 3383 (herb. Sohrabi).