Fomitiporia subtilissima Alves-Silva, Reck, & Drechsler-Santos, sp. nov.
Index Fungorum number: IF 551916, Facesoffungi number: FoF 01832, Fig. 2
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 [6 C(7 – 8)] to brown [6 E(5 – 8)], becoming dark brown [6 F(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 = 107 μm); 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 – 5 μm diam., the lumen 1 – 3 μm wide, in the hymenophoral trama 3.5 – 4.5 μm diam., the lumen 1 – 3 μm 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 × 8.1 μm) Q = 1 – 1.3 μm (mean Q = 1.14 μm); basidiospores subglobose, globose to obovoid, the wider portion displaced towards the apex, 4 – 5 × 4 – 4.5(–5) μm (mean = 4.5 × 4 μm) Q = 1 – 1.25 μm (mean Q = 1.13 μm) (n = 40), hyaline, slightly to moderately dextrinoid and cyanophilous, thick-walled and smooth.

Material examined — BRAZIL, Santa Catarina, Blumenau, Parque NaturalMunicipal 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. Themorphologic and molecular data (BS =100, BPP=1) high support the new species. The phylogenetic analysis (Fig. 1) recovered F. subtilissima in a clade nested with F. atlantica and another undescribed species from Brazil.

Fig. 1 Phylogram generated from Maximum Likelihood (RAxML) analysis based on combined nrLSU, nrITS, EF and RPB2 sequence data of Fomitiporia. Maximum Likelihood bootstrap support values greater than 70 % and Bayesian posterior probabilities (BPP) greater than 0.98 are indicated above and below the nodes (BS/BPP). In the BI analysis average standard deviation of split frequencies = 0.005 and the bootstopping criteria of RAxML indicated 204 pseudoreplications as sufficient to access the internal branch support. New taxa are in blue and species for which obtained sequences are based on type material have names in bold. The tree is rooted with Phellinus uncisetus.

Fig. 2 Fomitiporia subtilissima (FURB 47437) a Basidiomata in situ c Abmenial surface showing the concentric zonation and spathulate aspect of basidioma. Fomitiporia subtilissima (holotype) f, g Details of context and tubes f Black line at the surface g Context and tube layers j Hymenophoral surface m Basidiospores.
Fomitiporia atlantica (FURB 47591) b Darkness aspect of basidiomata in situ e Abhymenial surface h Black line at the surface k Nodulous basidioma l Hymenophoral surface n Basidiospores. Fomitiporia atlantica (holotype) d Detail of slightly cracked abhymenial surface i Context and tube layers. Scale bars: a, b = 50 mm, c – e, g and i, l = 20 mm, f, h = 2 mm, m, n = 5 μm.