Myriolecis zosterae (Ach.) Sliwa, Zhao Xin & Lumbsch
Lecanora zosterae (Ach.) Nyl.
Thallus very thin or evanescent, sometimes hardly visible (though some algae or a thallus of a different species may be present nearby), dull whitish, pale grey, pale grey-greenish, prothallus not apparent. Apothecia usually numerous, scattered or in clusters, peltate (attached to the substratum by a central point and appearing stalked), 0.5-2 mm diam., sometimes up to 2-3.5 mm diam. on favourable substrata (ligneous debris), disc smooth, flat becoming slightly concave, brown, dark brown, brown-blackish but also pale brown-pink or pale brown-greenish when very moist, exciple thin, persistent, more or less flexuose, whitish to pale white-greenish. Asci, 40-50 x 16-18 µm according to our measures. Ascospores simple, ovoid, 9-14 x 4-6 µm. Photobiont: Trebouxia. Thallus (when present) and apothecia without significant chemical reactions: C-, K-, KC-, Pd-. Maritime species, usually grows on dying or dead plants, notably on roots and branches of Armeria maritima to the very close limit of the shore, also on driftwood, or wooden ship wrecks, decaying woods, wood poles near the seashore, all of them subjected to seespray and submersion, in all cases on a very moist substratum and even continuously impregnated of sea-water. This species currently is under decline due to coastal works and destructions related to oil spills and marine erosion. Nowadays this species which formerly was described on decaying dead Armeria maritima roots seems to be restricted to rotten wooden ship wrecks left over in remote areas of harbours, and always on a very humid substratum permeated with seawater.
N.B. Not to be confused with with Pezizales growing on deacaying wood.
N.B. Other Lecanora species able to grow in this habitat type have smaller and less sessile apothecia, though more numerous, a crustose thallus and positive chemical spot tests. This species was and still is highly variable and consequently was diversely analyzed. Tentatively we might consider that these different forms belong to a cluster of related taxa sharing a common habitat, decaying plants or bare wood (including in alpine and Arctic sites), negative chemical reactions and markedly sessile to almost stalked apothecia. It is also possible that in this species are included forms of Myriolecis (Lecanora) hagenii var. hagenii forma gregata in particular for the specimens coming on wood.
N.B. There is a transitional form between Myriolecis hagenii morpho hagenii on bare wood or bark at the base of seaside trees and Myriolecis zosterae, this is Myriolecis hagenii forme lignicole de la zone aérohaline.