Xylodon exilis Yurchenko, Riebesehl & Langer

Riebesehl, Janett, Yurchenko, Eugene, Nakasone, Karen K. & Langer, Ewald, 2019, Phylogenetic and morphological studies in Xylodon (Hymenochaetales, Basidiomycota) with the addition of four new species, MycoKeys 47, pp. 97-137 : 97

Xylodon exilis Yurchenko, Riebesehl & Langer sp. nov. Figs 3a, 4

Holotype.

TAIWAN, Nantou county, south from Sun-Moon Lake, near Hua Lien, Lien-Hwa-Chi, 700 m a.s.l., on fallen angiosperm twig, leg. E. Langer, G. Langer, F. Oberwinkler, 10 Jul 1990 (TUB-FO 42565; isotypes in KAS and MSK).

Description.

Basidiomata effused, 1-5 cm in extent, membranaceous, discontinuous at the periphery. Hymenial surface minutely odontioid, cream-coloured, between aculei 50-130 μm thick. Aculei peg-like, conical or subcylindrical, entire or slightly penicillate apically, 35-70 μm long, 15 –50(– 70) μm diam., 8-14/mm. Margin abrupt or somewhat thinning out. Hyphal system monomitic, hyphae colourless, with clamps at all primary septa. Subicular hyphae forming a loose tissue, rarely branched, 3 –4(– 4.5) μm wide, with slightly thick to thick walls (0.5-1.2 μm thick), with scattered adventitious septa, smooth. Subhymenial hyphae in a dense tissue, richly branched, 2-3 μm wide, thin-walled, smooth or slightly encrusted. Capitate cystidia enclosed, 18-22 × 5.5-8 μm, sometimes with an adventitious septum in stem, thin- to slightly thick-walled. Projecting hyphae in aculei flexuous, apically obtuse, 90-130 μm long, 3-4 μm wide, originating from thick-walled subicular hyphae, with simple and clamped septa, often constricted at septa, walls thickened at base then gradually thinning toward apex, moderately encrusted. Basidioles clavate or bowling pin-shaped, 10-20 × 4.5-5.5 μm. Basidia narrowly utriform, 20-25 × 4 –5(– 5.5) μm, thin-walled, smooth, with four sterigmata 2-4 × 0.3 μm. Spores narrowly ellipsoid, 5.5-6 × 2.5-3 μm, holotype L = 5.8 µm, W = 2.8 µm, Q = (1.6 –)1.8– 2.2, colourless, smooth, slightly thick-walled, negative in Mz, acyanophilous, with minute apiculus.

Distribution and ecology.

The species is known from Taiwan and Nepal. It grows on dead wood of angiosperms, with a preference for small branches and twigs.

Etymology.

from Latin exilis - thin, fine, refers to the small and narrow aculei.

Additional specimens examined.

TAIWAN, Nantou Co., west from Sun-Moon Lake, near Hua Lien, on dead wood, leg. E. Langer, G. Langer, F. Oberwinkler, 26 Mar 1989 (TUB-FO 40734; dupl. in KAS); south from Sun-Moon Lake, near Hua Lien, on fallen angiosperm twig, leg. E. Langer, G. Langer, F. Oberwinkler, 9 Jul 1990 (TUB-FO 42450; dupl. in KAS and MSK); Taichung Co., Shinshe, on fallen angiosperm twig, leg. E. Yurchenko, 2 Apr 2011 (MSK-F 12912); ibid., on fallen liana stem, leg. E. Yurchenko, 2 Apr 2011 (MSK-F 12913); ibid., on fallen angiosperm twig, leg. E. Yurchenko, 5 Jun 2011 (MSK-F 12914); Taipei Co., Wulai, Neidong Recreation Area, on fallen angiosperm twig, leg. E. Yurchenko, 23 Jun 2011 (MSK-F 7381; dupl. in KAS and LE); Miaoli Co., Sanyi, on fallen angiosperm branch, leg. E. Yurchenko, 3 Jul 2011 (MSK-F 7431); ibid., on fallen angiosperm branch, leg. E. Yurchenko, 19 Jul 2011 (MSK-F 7430). NEPAL: Gandaki Prov., Kuldi, Anapurna Trek, leg. L. Ryvarden, 7 Nov 1979 (O-LR 18918/B, dupl. in KAS).

Remarks.

The species concept of X. lanatus is revised and restricted to specimens with a well-developed woolly subiculum. The distinctive characters of X. exilis are the minutely odontioid basidiomata with peg-like aculei composed of flexuous, encrusted, septate projecting hyphae that are constricted at the septa, embedded capitate cystidia and narrowly ellipsoid spores with slightly thickened walls. Earlier specimens of X. exilis from Taiwan (e.g. Langer 1994, p. 143 for illustration) and Nepal ( Hjortstam and Ryvarden 1984) were originally identified as X. lanatus . Hyphae and spores of this species were also depicted by Yurchenko et al. (2013) under the name X. lanatus . These two species and other morphologically similar taxa are compared in the Discussion section below; a key is also presented.