Fomitiporia subtilissima – Facesoffungi number: FoF 01832

Fomitiporia subtilissima Alves-Silva, Reck, & Drechsler-Santos

Index Fungorum number: IF 551916 Facesoffungi number: FoF 01832

Etymology: referring to the relatively thin basidiomata.

Holotype: FURB 47557. 

Basidiomata perennial, pileate; sessile, subdimidiate to pseudostipitate, the pseudostipe formed by successive deposited layers, single or with distinct pilei developing from the same point, semicircular, flabelliform to slightly spathulate, aplanate to convex, in section and near the base slightly obtriquetrous, projecting 18–162 mm, 17–96 mm wide and 6–40 mm thick at the base, soft, woody consistency; pileus glabrous,concentrically zonated with multiple narrow bands, moderately sulcate, light brown [6 D(5–8)], brownish orange [6C(7–8)]tobrown[6E(5–8)],becomingdarkbrown [6F(5– 8)] to black; margin acute to obtuse, sterile, light brown [5 D(6–8)] to yellowish brown [6 E(5–8)]; pore surface grayish brown [6 F(3)] to cinnamon, near the base the newest tube layer presents an wider sterile yellowish brown [5 D(6–8)] margin (up to 2 mm), contrasting with the precedent layer recovered by brown [6 E(6–8)]context; pores rounded to angular, (4–)5 –9 per mm, (70–) 80 –131 (–170) μm diam. (mean=107μm); dissepiments entire, 30–76 (–100) μm (mean=45μm) thick; tubes distinctly stratified, up to 9 layers, individual layers 0.3–3 mm thick, with context among it, up to 2 mm thick, greyish brown [6 F(3–4)] to brown [6 E (6–8)], but the youngest (active) layer greyish brown (6E4) to cinnamon, the older layers filled with whitish mycelium; context simple, concentrically zonate, up to 6 mm thick, with soft and hard to woody consistency, light golden brown to light brownish yellow [5 BC (7–8)], with a distinct dark line at the surface. Hyphal system dimitic in all parts; generative hyphae simple septate, hyaline to pale yellow, mildly branched, 1.5–2( –2.5) μm diam; skeletal hyphae golden brown to reddish brown, unbranched, thick-walled, occasionally with constrictions uncompleted becoming local swellings up to 8μm diam., in the context 3–5μm diam., the lumen 1– 3μm wide, in the hymenophoral trama 3.5–4.5μm diam., the lumen 1–3μm wide. Hymenium: hymenial setae absent, other sterile elements presents (as basidioles), hyaline, thin-walled; basidia subglobose to globose, hyaline,tetrasporic, 9–10×7– 9 (mean=9.2×8.1μm) Q=1 –1.3μm (meanQ=1.14μm); basidiospores subglobose, globose to obovoid,the wider portion displaced towards the apex, 4–5×4–4.5(–5) μm (mean=4.5×4μm) Q=1 –1.25μm (meanQ=1.13μm) (n=40), hyaline, slightly to moderately dextrinoid and cyanophilous, thick-walled and smooth.

Material examined: BRAZIL, Santa Catarina, Blumenau, Parque Natural Municipal São Francisco de Assis, 26°55′17″S 49°04′18″W, growing on dead root of living Sloanea guianensis (Aubl.) Benth. (Elaeocarpaceae), 28 July 2015, F. Bittencourt 493 (FURB 47557, holotype, isotype in FLOR); Ibid., in the base of a living unidentified angiosperm, 13 May 2015, F. Bittencourt 428 (FURB 47437).

Notes: The flabelliform to spathulate, thin and aplanate basidiomata, with the presence of a pseudostipe, and the narrow concentrically zonated and sulcate abhymenial surface characterizes this species as unique in the genus. The pseudostipe is explained by its successive depositing forward tube layers that do not cover the precedent layer near the base. Besides, F. subtilissima has slightly to moderately dextrinoid basidiospores, which are relatively small when compared with other Fomitiporia species. Due to its macroscopic features, F. subtilissima resembles some Phylloporia species, but this genus is characterized by monomitic hyphal system and IKIbasidiospores. Variably dextrinoid small basidiospores are also found in F. gabonensis and F. ivindoensis Decock, Amalfi & Yombiyeni (Amalfi et al. 2010), both described from Gabon, Africa. Fomitiporia gabonensis has thick, obtriquetrous and broadly attached basidiomata, while F. ivindoensis has cushion-shaped to aplanate basidiomata, but they do not have pseudostipe. The morphologic and molecular data (BS=100, BPP=1) high support the new species. The phylogenetic analysis recovered F. subtilissimaina clade nested with F. atlantica and another undescribed species from Brazil.