Fomitiporia subtilissima Alves-Silva, Reck & Drechsler-Santos

2. Fomitiporia subtilissima Alves-Silva, Reck & Drechsler-Santos, in Li et al., Fungal Diversity 78 (2016). Figs. 3 a-c; 9b Basidiomata perennial, pileate, woody, sessile to pseudostipitate due to concrescence of layers, aplanate, flabelliform, dimidiate, convex to elongate, single or laterally connate and thus horizontally imbricate, gregarious, growing at the base and roots of trees, 4–22 × 4.5–15.5 cm, up to 1.5 cm thick. Abhymenial surface zonate, concentric zones slightly to strongly sulcate and narrow, crustose, dark brown to reddish-brown, glabrous, rimose, often with moss growing on. Margin obtuse, copper-brown, glabrous. Context homogeneous to slightly zonate, fibrous, with a resinous dark line near the abhymenial surface, golden-brown to slightly reddish-brown, up to 7 mm. Tubes unistratified to pluristratified, concolorous, up to 6 mm thick, old ones filled with white mycelium. Hymenial surface poroid, brownish-gray to copper gold. Pores invisible to the naked eye, round to slightly angular, (7–)8–9(–10) per mm. Dissepiments thick, tomentose, entire. Hyphal system dimitic. Generative hyphae more easily observed at the dissepiment, simple septate, hyaline, thin-walled, rarely with refringent content, 3–5(–6) μm diam. Skeletal hyphae dominant, moderately to strongly dextrinoid, thick-walled to solid, sulfurous-yellow to reddish-yellow, often aseptate to occasionally septate, sparingly branched, with or without refringent content, 3–5(–7) μm diam. Setae absent. Basidia not found. Basidiospores rare to frequent, subglobose to globose, slightly to moderately dextrinoid, hyaline, thick-walled, without content, (4.4–)4.5–5.2(–5.5) × (4.1–)4.2–5(–5.2) μm, Lm × Wm = 4.8 × 4.3 μm; Q = 1–1.18(–1.2), Qm = 1.1 (n = 24/2). Material examined: Juquitiba, São Paulo Green Belt Biosphere Reserve, Trilha da Chama Violeta, 9.II.2022, F. Pagin et al. FP 504 (SP 528834); 14.VII.2022, F. Pagin et al. FP 548 (SP 527875). G rowing on angiosperm wood (Li et al. 2016). The species was found in Brazil (Li et al. 2016). Previously recorded from the Brazilian Atlantic Forest in the state of Santa Catarina (Li et al. 2016). This is the first record from the Southeast of Brazil. The type locality of Fomitiporia subtilissima is Blumenau, Santa Catarina, Brazil (Li et al. 2016). Fomitiporia subtilissima can be recognized in the field by its perennial, gregarious, aplanate, sessile to pseudostipitate basidiomata, narrowly sulcate abhymenial surface, dark resinous line in the context, obtuse margin, brownish-gray to coppergold hymenial surface, and by pores which are invisible to the naked eye as well. In addition other diagnostic features are its globose and dextrinoid basidiospores with 4–6 μm in diam. and not surpassing 6 μm in diam. (Alves-Silva et al. 2020). This set of morphological features used to identify F. subtilissima is quite unique within the genus. In our fungal inventory, as well as in Li et al. (2016), basidiomata were collected from the base and roots of trees, both dead or alive, suggesting that this species may oscillate between being a parasite and a saprotroph.