Skeletocutis futilis 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 futilis Miettinen & A. Korhonen sp. nov. Figure 7

Holotype.

Finland. Uusimaa: Helsinki, Sorbus aucuparia , 24 Sep 2012 Miettinen 15745 (H 7008667).

Description.

Basidiocarps annual; half-resupinate; small, up to 5 mm wide and 1.5 mm thick; hard when dry but easy to break apart; pilei very small and nodulous; upper surface white when young, turning yellowish-brown; context and subiculum white; tube layer up to 0.2 mm thick; pores 6-8 per mm.

Hyphal structure: skeletal hyphae in context / subiculum (1.0 –)2.0–3.0(– 3.3) µm wide, in trama scarce, (1.0 –)2.0–3.9(– 4.9) µm wide, generative hyphae in trama 1.0 –2.0(– 3.2) µm wide.

Basidiospores 3.0 –4.0×0.7– 0.9 µm, L=3.33 µm, W=0.81 µm, Q’=(3.3–)3.4– 5.1, Q=4.13, n=30.

Distribution and ecology.

The species is known only from the type specimen which was collected from a Betula stand on a disturbed site near the seashore in Helsinki, Finland (hemiboreal zone) where it was growing on rather thin twigs of Sorbus aucuparia .

Etymology.

Futilis (Lat.), fragile, insignificant.

Specimen examined.

FINLAND: Uusimaa: (holotype, see above).

Discussion.

While macroscopic features may be quite scanty, characteristic trimitic-looking subiculum, skeletal hyphae in trama and encrustations of dissepiment edge hyphae reveal S. futilis to be a member of the S. nivea complex. S. futilis can be distinguished from other species in the complex by thicker spores.

In our analyses, S. futilis constitutes a sister taxon to the rest of the S. nivea complex. The clade also includes S. aff. futilis in North America. Owing to the limited material available, we refrain from judging whether they represent geographic variation within one species or vicariant sister species. The voucher specimens of S. aff. futilis (Lindner DLL2009-067; -068 (CFMR)) are in a rather poor condition, but it seems that the small size of basidiocarps and thick spores are as characteristic for S. aff. futilis as they are for S. futilis .