Riopa pudens Miettinen

Miettinen, Otto, Spirin, Viacheslav, Vlasak, Josef, Rivoire, Bernard, Stenroos, Soili & Hibbett, David S., 2016, Polypores and genus concepts in Phanerochaetaceae (Polyporales, Basidiomycota), MycoKeys 17, pp. 1-46 : 24

Riopa pudens Miettinen sp. nov. Figure 9h

Holotype.

Indonesia. Riau: Indragiri Hulu, Bukit Aluran Babi, -0.838: 102.226, selectively logged forest slope, piece of a dicot log (15 cm in diameter, decay stage 2-4/5), 1 Jul 2004, Miettinen 8772 (ANDA, isotype H 7008582).

Etymology.

Pudens (adj., L), shy, modest, refers to the scarcity of distinct characters.

Description.

Basidiocarp resupinate, annual, cream, young parts white, up to half a meter wide, up to 4 mm thick. Consistency resistant to breaking but not tough. Pores thin-walled, mouths finely dentate, splitting when older, angular, 4-5 mm, 2-3 per mm when split/fused, 0.5-1.2 mm long. Subiculum white, 0.1-0.4 mm thick. Margin thinning out.

Hyphal system monomitic, clamps absent. Hyphae not swollen, rather similar in all parts. Subicular tissue loose, hyphae interwoven, thin- to thick-walled, mostly slightly thick-walled, (2.8)3.4-4.8(6.2) µm in diameter, walls rarely up to 1 µm thick. Tramal hyphae vertical, subparallel to interwoven, only moderately winding, thin-walled or slightly thick-walled, (2.4)2.8-3.2(4.2) µm in diameter. Shiny hyaline resin droplets floating around, fine-grained crystalline-amorphous substance glued on tramal hyphae in CB.

Cystidia not seen.

Hymenium relatively loosely arranged, basidia very thin-walled, collapsing soon, basidioles 10 –14×3– 4.2 µm.

Basidiospores curved cylindrical, thin-walled, (4.2)4.3 –5.6(6.2)×(1.8)1.9– 2.2(2.3) µm, L=5.01 µm, W=2.08 µm, Q=2.41.

Distribution.

Southeast Asia. Known from Riau, Sumatra and Fujian, China (the INSDC sequence JX623931, Cui 3238, ' Ceriporia camaresiana ').

Ecology.

Grows on fairly rotten angiosperm wood. The type comes from low-land rainforest.

Remarks.

The species lacks any distinct characters. Cream-colored basidiocarp with non-inflated hyphae and corymb-subhymenium help to distinguish this species from Ceriporia spp. It is similar to Phanerochaete inflata and Ceriporia jianxiensis , but differs in having long-celled, narrower subicular hyphae (mostly <5 µm in diameter). The relatively small cylindrical curved spores exclude Oxyporus spp. and Emmia spp. Except for the smaller pores and the lack of cystidia and a conidial stage it is very similar to Riopa metamorphosa .