Irpiciporus rajchenbergii Nakasone 2022

Regio, Nicolas Do Carmo, Westphalen, Mauro C. & Silveira, Rosa Mara Borges Da, 2024, Studies on Neotropical Cerrenaceae (Basidiomycota, Polyporales): a new species of Irpiciporus from Brazil, Phytotaxa 675 (3), pp. 217-232 : 225-227

Irpiciporus rajchenbergii Nakasone 2022 Fig. 5

Mycobank: MB 844558

Type:— BRAZIL. Rio Grande do Sul, São Leopoldo, 1931, Rick s.n. ( BPI 0259635, holotype).

Comments:— Irpiciporus rajchenbergii is a resupinate species described based on specimens collected by Rick in Southern Brazil and deposited at BPI herbarium. The collections were previously identified as “ Hydnum macrodon ”, and their circumscription in Irpiciporus was put in doubt by Miettinen et al. (2023), mostly due to the presence of a hydnoid hymenophore and morphological analysis based on a restricted number of old specimens. We were able to examine several specimens, studied and determined by Rick as H. macrodon , deposited at PACA herbarium and can confirm its circumscription in Irpiciporus , since it presents high morphological similarity with other species in the genus. Although we could not analyze the holotype ourselves, we compared the specimens examined with the description provided by Nakasone & Ortiz-Santana (2022), along with photos of the type provided by the BPI staff.

Irpiciporus rajchenbergii is microscopically similar to I. prismaticus , including the presence of prismatic crystals in the subiculum and teeth trama, which were not cited in the original description. However, they can be differentiated by the effused-reflexed to pileate basidiomes, thicker and smaller teeth (1.5–3.5 mm long) and considerably smaller basidia (16.5–23 µm long) in I. prismaticus . Furthermore, we were able to observe the presence of incomplete pores on the margin of the basidiomes, indicating that the species could be classified as irpicoid as well. Still, we corroborate that the species has a mostly hydnoid hymenophore composed of narrowly conical spines, as described by Nakasone & Ortiz-Santana (2022).

Additionally, another five PACA collections from the same region and identified as “ Irpex mollis ” were examined and probably represent a different species in Irpiciporus . The specimens presented many basidiospores, but no basidia or prismatic crystals were observed. They differ from I. rajchenbergii by the pileate basidiomes with smaller teeth (2–4 mm long) and from I. prismaticus by the incomplete pores near the margin and slightly thinner basidiospores 4–6 × 3.5–5.2 µm (Qm = 1.18 µm). Although it is possible, we strongly doubt that I. mollis s. s. occurs in South America, even so, the basidiospores resemble more those of I. pachyodon . These collections should be taken into consideration when revising Neotropical specimens.

Specimens examined as Hydnum macrodon :— BRAZIL. Rio Grande do Sul, São Leopoldo, 1905, Rick s.n., 16575 ( PACA) ; ibid. 1907, Rick s.n., 16504 ( PACA) ; ibid. 1933, Rick s.n., 16553 ( PACA) ; ibid., Rick s.n., 16558 ( PACA) ; ibid., Rick s.n., 16567 ( PACA) ; URUGUAY. Taquarembó, 1936, Rick s.n., 16584 ( PACA) .

Additional specimens examined as Irpex mollis :— BRAZIL. Rio Grande do Sul, São Leopoldo, 1932, Rick s.n., 16693 ( PACA); ibid. Rick s.n., 16672 ( PACA); ibid., Rick s.n., 16676 ( PACA); Santa Maria, 1935, Rick s.n., 16645 ( PACA).

Figures

FIGURE 5. Morphological characters of Irpiciporus PACA collections. A–C. I. rajchenbergii; A. Basidiome margin (PACA 16567); B. Hymenophore (PACA 16553). C. Subiculum with prismatic crystals (PACA 16575); D. I. aff. mollis (PACA 16693). Scale bars:A = 2 cm; B-C = 1 mm; D = 1.25 mm. Photos: Nicolas Regio.