Pseudobaeospora cyanea Arnolds, Tabares & Rocabruna

Pseudobaeospora cyanea Arnolds, Tabarés & Rocabruna, Revta Catal. Micol. 25: 66 (2003) Figs 4 b, 13 Holotype. SPAIN • Catalonia, Girona, La Selva, surroundings of Mas de Llagostera (UTM 31 T 0480 4622), 200 m, on acidic, humus-rich soil above granite, in forest with Pinus pinaster, Quercus suber, Arbutus unedo and Erica arborea, probably saprobic, 6 November 2002, leg. J. Carreras & M. Tabarés, (BCN SCM B-4742). Selected iconography. Arnolds et al. (2003: 69), Arauzo (2011 a: 24, 26), Gisotti et al. (2021: fig. 1). Selected descriptions. Arnolds et al. (2003: 66–68), Arauzo (2011 a: 23, 25), Gisotti et al. (2021: 123–125). Description. Spores (4.0 –) 4.5–4.8 – 5.2 (– 5.4) × (2.9 –) 3.5–3.7 – 4.0 (– 4.2) μm (64 / 1 / 1), Q = (1.10 –) 1.21–1.31 – 1.40 (– 1.51), V = (19.7 –) 29.2–35.2 – 41.3 (– 48.0) μm 3, broadly ellipsoid to ellipsoid, slightly amygdaliform in side view, walls up to 0.8 µm thick and dextrinoid at maturity, smooth, colorless in L 4, hilar appendix prominent, 0.8–1 µm long. Basidia 21–25 × 6.5–8.0 µm, some with up to 1 μm thick wall (crassobasidia), tetrasporic, rarely bisporic to monosporic, clavate, sterigmata up to 4.5 µm long. Hymenophoral trama regular to subregular, composed of up to 12 µm wide cylindrical to inflated hyphae, colorless in L 4. Cheilocystidia 15–30 (– 34) × 3–7 (– 11) µm, rare, scattered, basidiola-like to irregularly cylindrical, lageniform, sometimes lobed to furcate. Pleurocystidia present, very rare, similar to cheilocystidia but bigger, up to 56 × 12 µm. Pileipellis: suprapellis (at the pileus centre) a transition between trichoderm and epithelium consisting of loosely entangled ascending and erect pluriseptate hyphae, terminal elements broadly cylindrical, clavate to subglobose, up to 18 µm wide; towards the pileus margin it tends to become a cutis with repent hyphae; pigment abundant, brownish grey, bluish, intracellular and encrusting (extracellular), green in KOH; pileitrama consisting of up to 8 µm wide cylindrical hyphae. Stipitipellis consisting of 2–4 µm wide, multiseptate, parallel, cylindrical hyphae. Stipititrama similar to the stipitipellis structure but with 3–6 µm wide hyphae. Caulocystidia 10–70 (– 80) × 3.0–7 µm, filiform, sinuous, often multiseptate, sometimes irregularly lobed and furcate. Clamp-connections present everywhere. Specimen examined. ITALY • Liguria, Pegli (GE), 95 m, in an area of shrub-like Mediterranean vegetation with Pinus pinaster Aiton, Arbutus unedo L., Erica arborea L., Cistus salvifolius L., and Quercus ilex L., on poor acidic soil with serpentine bedrock, in the needle litter of P. pinaster, 6 December 2016, leg. D. Gisotti & F. Boccardo (GDOR: M 3986). Notes. The species was originally described from Spain (Arnolds et al. 2003; Arauzo 2011 a) and then recently found in Liguria, Italy (Gisotti et al. 2021). Pseudobaeospora cyanea is clearly distinguished from the other species by a unique combination of features such as a bright bluish-purple pileus, pale lamellae and stipe, a trichodermic structure of the pileipellis (with inflated elements), green reaction of the pileipellis to KOH and well-developed cheilocystidia (Arnolds et al. 2003). Our microscopic analysis of the collection studied by Gisotti et al. (2021) (GDOR: M 3986) revealed the presence of rare pleurocystidia which were not recorded by previous authors. Pleurocystidia were so far only reported for P. aciculifera Voto & Soop (Voto and Soop 2018), and P. taluna (Craig et al. 2023), two species of the southern hemisphere. Both Spanish and Italian collections were made in Mediterranean areas in winter, viz. Mediterranean hills with Pinus pinaster, Arbutus unedo and Erica arborea (Arnolds et al. 2003), and an area of shrub-like Mediterranean vegetation with P. pinaster, A. unedo, E. arborea, C. salvifolius, and Q. ilex (Gisotti et al. 2021), respectively. The morphology of the Spanish and Italian collections compared was completely consistent. In the multigene analysis (Fig. 2) the most closely allied species is P. lilacina X. D. Yu, Ming Zhang & S. Y. Wu from China (Wu et al. 2017), which is distinguished by a pileus surface pale mauve, colonial buff when old, smaller spores 2.5–3.5 (– 4.5) × 3–5 (– 6.5) μm, cheilocystidia absent, and pileipellis hyphae not changing color in 5 % KOH. Pseudobaeospora pallidifolia Bas, A. Gennari & Robich from mossy coniferous forest in Tuscany (Italy) so far known only from the type locality, is similar to P. cyanea by the dark pileus with paler margin strongly contrasting with whitish to pinkish cream lamellae and the pale stipe, but differs by lack of cheilocystidia, and comparatively large and more elongated ellipsoid spores 4.4–6.4 × 3.3–4.4 μm, Q = 1.30–1.40 (Bas et al. 1997; Bas 2003).