Fomitiporia robustiformis Jian Chen, Yuan Yuan, K. Y. Luo, Y. C. Dai & Vlasak 2025, sp. nov.

Fomitiporia robustiformis Jian Chen, Yuan Yuan, K. Y. Luo, Y. C. Dai & Vlasák sp. nov. Figs 2, 3 Diagnosis. Fomitiporia robustiformis is closely related to F. texana (Murrill) Nuss and F. deserticola Vlasák, but F. texana differs from F. robustiformis by the presence of hymenial setae and cystidioles, larger basidiospores (7–9 × 6.5–9 µm vs. 5–6.4 × 4.7–6.1 µm). F. deserticola is distinguished from F. robustiformis by the presence of abundant cystidioles and larger basidiospores (6–7.5 × 5.5–7 µm vs. 5–6.4 × 4.7–6.1 µm). Holotype. Ecuador • Arenillas, dry tropical forest, on living Acacia sp., 17.II.2024, leg J. Vlasák, JV 2402/8 (BJFC 053711). Etymology. Robustiformis (Lat.) refers to a new species characterized by robust basidiomata. Description. Basidiomata perennial, pileate, inseparable, sessile, without distinctive odor or taste when fresh, woody hard in consistency, light in weight when dry; pilei ungulate, fan-shaped, projecting up to 5 cm, 5 cm wide, and 3 cm thick at base; pileal surface brown, sometimes greenish from algae, glabrous; margin broad and rounded. Pore surface pale mouse-gray when fresh, becoming yellowish brown when dry, not glossy; sterile margin brown, up to 1 mm wide; pores circular to angular, 6–7 per mm; dissepiments thin, entire. Context yellow-brown, woody hard, up to 7 mm thick; tubes pale gray to yellow-brown, paler than pore surface, woody hard, up to 2 cm long, annual layers indistinct. Hyphal structure. Hyphal system dimitic, generative hyphae simple septate; all hyphae IKI -, CB -; tissue becoming dark brown in KOH. Context. Generative hyphae frequent, pale yellow, slightly thick-walled, rarely branched, frequently septate, 3–3.5 µm in diam; skeletal hyphae dominant, yellowish brown, thick-walled, unbranched, more or less flexuous, interwoven, 3–4.5 µm in diam. Tubes. Generative hyphae pale yellowish, slightly thick-walled, rarely branched, frequently septate, 3–3.5 µm in diam; skeletal hyphae dominant, yellowish, thick-walled, unbranched, more or less straight, parallel along the tubes, 3–4.5 µm in diam. Hymenial setae absent; cystidioles present, fusoid, hyaline, thin-walled, 14–18 × 2.5–3.5 μm; basidia clavate, with four sterigmata and a simple septum at the base, 10–18 × 6–7.5 µm; basidioles dominant in hymenium, in shape similar to basidia, but slightly smaller. Basidiospores globose, hyaline, thick-walled, smooth, some with a guttule, IKI [+], CB +, (4.4 -) 5–6.4 (- 7.1) × (4.4 -) 4.7–6.1 (- 6.9) µm, L = 5.66 µm, W = 5.39 µm, Q = 1.05 (n = 30 / 1). Type of rot. White rot. Additional specimen (paratype) examined. Peru • Chongoyape, dry tropical forest, on a dead branch of a living angiosperm tree, 21.I.2025, leg J. Vlasák Jr., JV 2501/5-J.