Steccherinum subochraceum Bononi & Hjortstam

Steccherinum subochraceum Bononi & Hjortstam Figs 8 F, 9 F, 10 A, 11 H Description. Full description in Hjortstam and Bononi (1986). Mating system. Tetrapolar. Monosporic cultures obtained from specimen 730 / 22. Habitat and distribution. Known from the Atlantic Rainforest in southern and southeastern Brazil. Specimens examined. Brazil • Rio Grande do Sul: São Salvador, Montenegro, 04 Apr. 1945, Rick s. n. (PACA 22824 - holotype of Iprex hydenus Rick); • São Francisco de Paula, FLONA, 12 Mar. 2022, M. C. Westphalen 730 / 22 (ICN 213881); • ibid., 25 Nov. 2023, M. C. Westphalen 748 / 23 (ICN 213883); • Farroupilha, Parque dos Pinheiros, 22 Jul. 2023, M. C. Westphalen 746 / 23 (ICN 213882); • Canela, FLONA, 13 Jul. 2024, Westphalen 761 / 24 (ICN 313884). • São Paulo: São Paulo, Parque Estadual das Fontes do Ipiranga, 06 Oct. 1966, H. Requejo s. n. (SP 97591 - holotype). Notes. S. subochraceum was described from southeastern Brazil to provide a valid name for Iprex hydenus, originally described by Rick (1959) but considered invalid due to the lack of a designated type specimen. Among Neotropical hydnoid Steccherinum species, S. subochraceum is readily distinguished by the effused-reflexed basidiomes with notably long aculei (Figs 8 F, 10 A), usually measuring over 1.5 mm long (0.85–2.25 × 0.15–0.45 mm) (Table 4). Microscopically, it presents thin, elongated cystidia [25–60 (– 70) × 5–8 (– 10) µm] immersed in the trama, sometimes protruding at the apices of the aculei, and subglobose basidiospores measuring (3.2 –) 3.3–4.2 × 2.5–3.8 µm. Steccherinum larssonii and Steccherinum basibadium share a similar basidiospore size range (3.5–4.5 × 3.0–3.5 µm and 3.6–4.5 × 3.1–3.4 µm, respectively) but can be distinguished by their significantly shorter aculei, which reach a maximum length of 0.75 mm. In addition, Steccherinum basibadium forms more developed pilei with a brownish surface, whereas S. larssonii often produces completely resupinate basidiomes or only small pilei at the margins (Maas Geesteranus 1974; Westphalen et al. 2021). The subicular generative hyphae of S. subochraceum are regularly clamped, although simple-septate hyphae were observed in the trama of some specimens. Simple-septate hyphae were readily observed in specimen 746 / 23 but were less common in 730 / 22. Phylogenetically, S. subochraceum forms a sister clade to S. undigerum, a Neotropical species with somewhat similar basidiome morphology (effused-reflexed with imbricate pilei) and that also exhibits a strongly fimbriate mycelium in culture. However, S. undigerum differs in having a poroid hymenophore with dentate dissepiments and slightly larger basidiospores (4–5 × 3.5–4.5 μm).