Taxonomy
Sarrameana was circumscribed in 1973 by the lichenologists Antonín Vězda and Peter James for material from New Caledonia with an unusual spore type; because the fungus did not fit any known lecideoid genera, they erected a new genus with Sarrameana paradoxa as the type species and, pending broader study, placed it only tentatively in the Lecideaceae in the loose sense. The type collection comes from the Sarraméa area (Col d'Amieu Forestry Station), which also was the inspiration for the genus name. [2]
In Australasian treatments from the mid-2000s, Sarrameana paradoxa has been sunk into S. albidoplumbea on the grounds that the "tailed" ascospore tips used to separate the type are variable and not taxonomically reliable. [3] However, this synonymy has not been universally adopted: major global nomenclators continue to maintain entries for both names as separate species. [4] [5]
Description
Sarrameana forms a very thin, white crust on bark that blends into the substrate rather than having a sharp edge. In section it is two-layered: a very thin, alga-free upper rind made of loosely arranged colourless fungal threads (hyphae), and a lower layer embedded among the outer bark cells that contains the partner green alga (small spherical cells consistent with Trebouxia ). Routine spot tests used to screen for secondary metabolites (K, C and Pd) yield negative reactions. [2]
The sexual fruiting bodies are scattered black discs (apothecia) of the lecideine type—i.e. they have a dark, fungus-made rim rather than a rim built from the thallus. They are about 0.6–1.2 mm across with a thick, glossy margin and a flat to slightly convex, matt disc . Inside, the side-wall ( excipulum ) is developed only laterally and is built from simple, radiating hyphae packed with minute oil droplets; the hymenium (the spore-bearing layer) is 60–75 micrometres (μm) tall and becomes olive-black at the top. The filamentous sterile elements between the spore sacs (paraphyses) are simple , slender (about 1.5 μm wide) and essentially like those of the excipulum. Beneath the hymenium lies a 70–80 μm subhymenium of tightly cemented vertical hyphae. [2]
Asci (the spore sacs) are cylindric to clavate , eight-spored, with relatively thick walls and an apical tholus that stains blue with iodine (I+). The spores are the genus's diagnostic feature: each ascospore is long and narrow, one-celled and colourless, with both ends abruptly tapered into thread-like, hair-like tails about 15–18 μm long; in the ascus the spores are often coiled in a spiral. Measured including the tails, they are typically 55–80 × 3–4 μm and have very thin walls. Asexual structures (pycnidia) are small, black, hemispherical and sessile (roughly 0.1 mm); they produce simple rod-shaped conidia 6–7 × 0.5 μm with pointed ends. [2]
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