Skeletocutis coprosmae (G. Cunn.) 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 coprosmae (G. Cunn.) A. Korhonen & Miettinen comb. nov.

Basionym.

Poria coprosmae G. Cunn., Bulletin of the New Zealand Department of Industrial Research 72: 38 (1947).

Holotype.

New Zealand. Westland: Lake Mapourika, Coprosma , Nov 1946 J.M.Dingley (PDD 5252, studied).

Description.

Basidiocarps possibly perennial; resupinate to half-resupinate; up to 6 cm wide and 8 mm thick; hard when dry, breaking apart neatly; pilei fleshy, protruding up to 1.7 cm; margin blunt with narrow, sterile ridge on the underside; upper surface minutely rough, matted, white to cream coloured when young, turning ochraceous brown and finally blackish with age; pore surface sometimes with greenish-grey tints deep within the tubes in pileate part; context and subiculum whitish-cream colour to light greyish-brown near contact with substrate (in thick basidiocarps); context up to 5 mm thick, azonate; tube layer from 0.5-1.5 up to 6 mm thick and zonate in perennial basidiocarp, lighter horizontal zones appear where tubes are filled with arbuscule-like 'binding hyphae’; pores (6 –)7–8(– 9) per mm.

Hyphal structure: skeletal hyphae in context 2.0-4.3(-5.3) µm wide, in subiculum (1.0 –)2.0–3.5(– 4.2) µm wide, in trama 2.0 –4.0(– 5.0) µm wide, generative hyphae in trama 1.0 –2.3(– 3.0) µm wide.

Basidiospores 2.8 –3.2(–3.3)×0.5– 0.7 µm, L=2.98 µm, W=0.57 µm, Q’=(4.0–)4.3–6.0(– 6.4), Q=5.19, n=60/2.

Distribution and ecology.

Available material is very limited but suggests a rather wide, temperate Australasian distribution from Tasmania to southern New Zealand.

Specimens examined.

AUSTRALIA. Tasmania: Huon Valley, indet. angiosperm wood, 21 Nov 2006 Gates 1898 (H). NEW ZEALAND. Westland: (holotype, see above).

Discussion.

After examining the type, we have chosen to use a previously published name Poria coprosmae as the basionym for this Australasian species. P. coprosmae was described by Cunningham (1947) from Westland, New Zealand. He ( Cunningham 1965) later concluded that his P. coprosmae was the same as Polyporus semipileatus Peck but he treated them mistakenly under the name Tyromyces chioneus (Fr.) P. Karst., as explained by Buchanan and Ryvarden (1988).

In their type studies of Polyporaceae species described by Cunningham, Buchanan and Ryvarden (1988) place P. coprosmae in the genus Ceriporiopsis Dom., rejecting placement in Incrustoporia or Skeletocutis based on the absence of encrusted hyphae. Rajchenberg (1995), on the other hand, found the hyphal structure in the holotype and other collections of P. coprosmae in PDD more in line with that of S. nivea . Our studies of the holotype confirm this view with the addition that we also observed encrusted generocystidia and thin-walled skeletal hyphae in the trama, which are characteristic for the S. nivea complex. Macroscopically, the only other studied specimen from Tasmania looks quite different from the type. However, we could not identify any clear microscopic differences and cannot rule out the possibility that the macroscopic differences represent variation between developmental stages. Nevertheless, considering the level of crypticity in the S. nivea complex, we have reservations in stating that our sequenced specimens are truly conspecific with the old type. Thus, we refrain from assigning an epitype for now.

S. nivea occurs in the North Island of New Zealand and it is possible that these two species could overlap as S. nivea has been shown to extend respectively far into the temperate zone in the northern hemisphere. The type specimen is a thin and resupinate basidiocarp on a fallen branch of a Coprosma shrub. The Tasmanian specimen, on the other hand, has evidently been growing on coarse wood and is unique in having a clearly perennial habit with a zonate tube layer.