Xylodon detriticus (Bourdot) K.H. Larss., Viner & Spirin

Viner, Ilya, Spirin, Viacheslav, Zibarova, Lucie & Larsson, Karl-Henrik, 2018, Additions to the taxonomy of Lagarobasidium and Xylodon (Hymenochaetales, Basidiomycota), MycoKeys 41, pp. 65-90 : 72-73

Xylodon detriticus (Bourdot) K.H. Larss., Viner & Spirin comb. nov. Figures 5, 6c, 7

Basionym.

Peniophora detritica Bourdot, Revue Scientifique du Bourbonnais et du Centre de la France 23: 13. 1910. ≡ Lagarobasidium detriticum (Bourdot) Jülich, Persoonia 10: 334. 1979. Type. France. Auvergne: Allier, St. Priest, fern, 1.IX.1909 Bourdot 7226 (lectotype S! [F204453], designated by Eriksson and Ryvarden 1976: 703).

Description.

Basidiocarps effused, up to 5 cm in widest dimension. No differentiated margin. Hymenial surface white, smooth or warted, farinaceous. Hyphal structure monomitic, hyphae clamped, faintly cyanophilous, thin-walled. Subicular hyphae interwoven and frequently branched, (2.2 –)3.0– 5.9 μm in diam. (n=61/6). Tramal hyphae subparallel, subhymenial hyphae short-celled, (1.5 –)1.9– 3.5 μm in diam. (n=61/6). Large, rhomboid or stellate crystals abundant in trama and subiculum, 8-10.5 μm in diam. Cystidia of two types: a) large, thin-walled cystidia of subicular or tramal origin, cylindrical or clavate, rarely slightly thick-walled (wall not exceeding 1 μm thick), (30.0 –)58.9–110.0(–115.0)×4.1–8.5(– 9.6) μm (n=120/6), occasionally bearing 1-2 clamped septa, b) rare astrocystidia of subhymenial origin, with a stellate crystalline cap 10 –23×2– 3.1 μm, in some specimens difficult to find. Basidia suburniform, 4-spored, (12.2 –)13.1–20.0×(3.1–)3.4– 5.0 μm (n=61/6), thin-walled. Basidiospores clearly thick-walled, elliptical to broadly elliptical, usually with an oil-drop, (3.3 –)4.3–5.7(–6.1)×3.2–4.1(– 4.5) μm (n=190/6), L=4.92, W=3.69, Q=1.34, cyanophilous.

Distribution and ecology

. Europe (Czech Republic, France, Italy), on herbaceous remnants, once collected from pine bark at the same spot where it was found on fern remains.

Remarks.

Eriksson and Ryvarden (1976) selected Bourdot 7226 (in herb. S) as lectotype. They also treated Hyphodontia nikolajevae and Odontia pruinosa as synonyms. However, the type specimens of H. nikolajevae and O. pruinosa reveal small differences from the type material and other collections of X. detriticus studied by us. The main features of X. detriticus versus the two other taxa are narrower basidiospores (must be observed in cotton blue) and longer, narrower cystidia having no distinct intercalary inflation (Tables 2, 3, Figures 5, 6). Eriksson and Ryvarden (1976) attributed the differences in cystidia morphology between Bourdot’s specimen and types of H. nikolajevae and O. pruinosa to different stages of basidiocarp development. Our investigation indicates that the differences are genetic and species specific. Differences in basidiospore size and shape are detectable in CB but not in KOH, which could explain why they have gone unnoticed in earlier studies.

Hjortstam and Ryvarden (2009) added Hyphodontia magnacystidiata to the synonymy of X. detriticus . This species is, as far as we know, only known from the type, collected on dead wood of Populus in New York, USA ( Lindsey and Gilbertson 1977). It has an odontioid basidiocarp and its cystidia are similar to those of X. pruinosus (Table 3, Figures 6, 8). On the other hand, the basidiospore size is very close to X. detriticus (Table 2). In the absence of sequenced material, it is not possible to decide whether this is an independent species or not. Considering that the single specimen was growing on wood and that X. detriticus is not yet found in North America, we prefer to keep H. magnacystidiata as a synonym of X. pruinosus (see below).

Xylodon detriticus grows on ferns and grasses, developing thin farinaceous basidiocarps. The species evidently has a more southern distribution than X. pruinosus . Earlier reports of X. detriticus from woody substrates should be treated with caution and may represent X. pruinosus or as yet undescribed taxa.