Skeletocutis semipileata (Peck) Miettinen & A. Korhonen

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 semipileata (Peck) Miettinen & A. Korhonen comb. nov. Figures 4E; 6B, F

Basionym.

Polyporus semipileatus Peck, Annual Report on the New York State Museum of Natural History 34: 43 (1881).

Lectotype.

U. S. A. New York: Catskill Mountains, Acer spicatum , Aug 1880 Peck (BPI 220657 ISOTYPE, designated here). MycoBank No. MBT381253

Epitype.

U. S. A. New York: Essex County, Huntington Wildlife Forest, Betula sp. (branch), 15 Aug 2012 Miettinen 15536 (H 7008664, designated here, duplicate in BPI). MycoBank No. MBT381348

Description.

Basidiocarps annual; resupinate to half-resupinate; hard when dry, breaking apart neatly; resupinate basidiocarps up to 10+ cm wide; pilei nodulous to shelf-shaped, often laterally fused, up to 4 mm thick and protruding up to 1.5 cm, sometimes rather fleshy but often thin and sharp-edged with slightly incurved margin or with narrow, sterile ridge on the underside; upper surface slightly rough, matted, white to cream coloured when young, turning ochraceous and finally blackish with age; pore surface cream coloured with ochraceous or rarely faint salmon coloured tints, often a greenish-grey or turquoise tint emerges within the tubes particularly in the pileate part, sometimes in scattered blotches; context and subiculum coriaceous, white; context sometimes faintly zonate in longitudinal section; tube layer up to 2 mm thick; pores (7 –)8–9(– 11) per mm.

Hyphal structure: skeletal hyphae in context / subiculum (1.0 –)2.0–3.3(– 4.3) µm wide, in trama (1.0 –)2.0–3.9(– 5.0) µm wide, generative hyphae in trama 1.0 –2.1(– 3.0) µm wide.

Basidiospores (2.3 –)2.8–3.1(–3.3)×0.4–0.6(– 0.7) µm, L=2.97 µm, W=0.55 µm, Q’=(4.1–)4.7–7.0(– 7.5), Q=5.43, n=450/15.

Distribution and ecology.

Temperate holarctic, extending to south-boreal zone at least in Fennoscandia; on various angiosperm species, often on thin fallen branches but sometimes on coarse wood as well.

Specimens examined.

FINLAND. Uusimaa: Helsinki, indet. angiosperm (fallen branch), 9 Oct 2011 Miettinen 14917.4 (H); Kirkkonummi, Prunus padus (fallen tree), 24 Oct 2012 Miettinen 15835 (H). Etelä-Häme: Hämeenlinna, Lammi, Corylus avellana (fallen branch), 11 Sep 2002 Miettinen 6694 (H); Pohjois-Häme: Jyväskylä, Vuoritsalo, Juniperus communis (fallen trunk), 15 Jul 2017 Miettinen 21003 (H). NORWAY. Møre og Romsdal: Nesset, Ulmus glabra , 22 Sep 2006 Ryvarden 47279 (O 361851); Sogn og Fjordane: Luster, C. avellana , 25 Aug 2007 Gaarder 5136 & Dybwad (O 293503). POLAND. Podlaskie Voivodeship: Hajnówka, C. avellana , 18 Sep 2012 Korhonen 76 (H). RUSSIA. Khabarovsk Reg.: Khabarovsk Dist., Ilga, Actinidia kolomikta , 10 Aug 2012 Spirin 5142 (H); Nizhny Novgorod Reg.: Lukoyanov Dist., Sanki, C. avellana , 7 Aug 2005 Spirin 2326 (H). UNITED KINGDOM. Scotland: South Lanarkshire, P. padus (fallen tree), 6 Jul 2010 Miettinen 14114 (H). U. S. A. Massachusetts: Holden, Betula sp. (fallen branch), 6 Sep 2013 Miettinen 16823 (H); Minnesota: Waseca, Tilia americana (fallen branch), 18 Aug 2013 Miettinen 16693.1 (H); New York: (lectotype, see above); (epitype, see above); indet. angiosperm wood, 18 Aug 2012 Miettinen 15715 (H); Betula sp., 22 Sep 2013 Miettinen 17135 (H); Fagus grandifolia (fallen tree crown), 20 Sep 2013 Miettinen 17074 (H).

Discussion.

S. semipileata seems to be the most widespread species in the S. nivea complex and overlaps with many of the other angiosperm-dwelling species: in Europe with S. futilis and S. nemoralis ; in the Far East with S. lepida and S. nivea ; and in North America with S. aff. futilis and possibly with S. calida . Apart from S. (aff.) futilis , these species are almost impossible to distinguish from each other morphologically.