Collection location: Planalto das Cezaredas, Portugal [Click for map]
The specimen was found on my herbaria material on a piece of a small trunk of a shrub containing other lichens (collected at the date given to this observation). It consists of a greenish thallus with many small perithecia on it (with approximate size of .2 mm in diameter). It reminds a non-isidiate Porina sp. and, according to Ref.1 , there are some of them, also growing on bark/wood, very similar to this one: P. aenea, P. borreri and P. leptospora. To reach a classification is necessary to go to the microscopic data: My specimen has needle shaped ascospores, with approximate dimensions of 30-40 × 2.5-3 µm, more than 3 and less than 10 septate, inside cylindrical thin-walled asci (presumably 8 per ascum). The ascospores of the similar species cited above have the following features (from Ref. 1):
P. aenea: 3-septate, 1–20(–24)× 3.5–5 µm;
P. borreri: 6–7(–8)-septate, (22.5–)28–31.4–35(–40) × (3–)4.5–4.8–5(–5.5) µm;
P. leptospora: 6–7(–8)-septate, 30–55 × 3–4 µm.
Thus, if this is a Porina sp., certainly P. aenea can be ruled out (on the basis of the septation of the ascospores) and, probably, also P. borreri can be ruled out (on the basis of the widht of the ascospores). So, the closer is P. leptospora.
After reaching this conclusion I found Ref. 2, where P. leptospora was elevated to the rank of species, before it was considered a variety of P. borreri. The main reason given there is precisely the narrow, almost cylindrical ascospores, rarely tapering towards one end of P. leptospora in opposition to the fusiform or clavate-fusiform ascospores of P. borreri. The dimension for the ascopores of P. leptospora given there are: 37–50 x 2·5–3·5 (–4·0) µm, thus even closer to what I observed.
According to Ref. 1, Porina spp. have either Trentepohlia or (mostly in foliicolous species) Phycopeltis photobiont. I took some photos of the algal cells (see the attached photos) and the photobiont doesn’t seem to be a Trentepohlia, but I could not linked it to Phycopeltis as well. The identification of the photobiont will permit to be more confident on the identification.
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