Skeletocutis nemoralis A. Korhonen & Miettinen

Korhonen, Aku, Seelan, Jaya Seelan Sathiya & Miettinen, Otto, 2018, Cryptic species diversity in polypores: the Skeletocutisnivea species complex, MycoKeys 36, pp. 45-82 : 45

Skeletocutis nemoralis A. Korhonen & Miettinen sp. nov. Figures 4 A–B, 6C, 7

Holotype.

Finland. Åland: Lemland, Nåtö, Fraxinus excelsior (fallen branch), 9 Oct 2012 Korhonen 90 (H 7008662).

Basidiocarps annual; resupinate to half-resupinate; bone hard when dry, breaking apart neatly; resupinate basidiocarps up to 10+ cm wide; pilei nodulous to shelf-shaped, often laterally fused and fleshy, protruding up to 1.3 cm; sterile margin often quite pronounced especially in resupinate part; upper surface slightly rough, matted, white to cream coloured when young, turning ochraceous and finally blackish with age; pore surface sometimes with a greenish-grey or turquoise tint emerging within the tubes especially in the pileate part but sometimes in scattered blotches; context sometimes faintly zonate in longitudinal section; tube layer up to 2 mm thick; pores (6 –)7–8(– 10) per mm.

Hyphal structure: skeletal hyphae in context / subiculum (1.0 –)2.0–3.0(– 4.0) µm wide, in trama (1.0 –)2.0–3.9(– 5.0) µm wide, generative hyphae in trama 1.0 –2.2(– 2.9) µm wide.

Basidiospores (2.8 –)2.9–3.2(–4.0)×(0.4–)0.5–0.6(– 0.7) µm, L=3.04 µm, W=0.56 µm, Q’=(4.1–)4.8–6.3(– 7.8), Q=5.47, n=390/13.

Distribution and ecology.

Temperate Eurasia, found in Europe, Iran and Japan; on angiosperm wood, especially Fraxinus , preferring coarse substrates like thick branches or even logs.

Etymology.

Refers to the distribution area of the species in the nemoral zone.

Specimens examined.

FINLAND. Åland: Jomala, Ramsholm, Fraxinus excelsior (fallen branch), 10 Oct 2012 Korhonen 100 (H); 103 (H); Lemland, Nåtö, F. excelsior (fallen branch) 9 Oct 2012 Korhonen 86 (H); 89 (H); (holotype, see above); Corylus avellana (fallen branch) Korhonen 93 (H). NORWAY. Møre og Romsdal: Sunndal, Populus tremula , 24 Sep 2008 Gaarder 5257 (O 288578); Nord-Trøndelag: Verdal, Sorbus aucuparia , 30 Aug 2006 Klepsland JK06-S080 (O 284195); Sogn og Fjordane: Aurland, Tilia cordata , 10 Jul 2004 Brandrud 149-04 (O 166204). POLAND. Podlaskie Voivodeship: Białowieża National Park, Carpinus betulus (fallen branch), 15 Sep 2012 Korhonen 35 (H); F. excelsior (fallen branch), 15 Sep 2012 Korhonen 28 (H); 31 (H); 18 Sep 2012 Korhonen 83 (H).

Discussion.

S. nemoralis shares its wide distribution in Eurasia with similar-looking S. semipileata. Both species tend to form rather large, half-resupinate basidiocarps with fleshy pilei. S. nemoralis has slightly larger spores and pores than S. semipileata , but the distinction is probably too small for definitive identification.

In Europe, S. nemoralis does not reach as far to the northeast as S. semipileata and appears to be missing in continental Finland. At its north-eastern outpost in Åland Islands, S. nemoralis is rather common, especially in old coppice meadows where it prefers the wood of Fraxinus .