Pluteus izurun P. Arrill. & Justo, 2014

Jr, Nelson Menolli, Justo, Alfredo, Arrillaga, Pedro, Pradeep, C. K., Minnis, Andrew M. & Capelari, Marina, 2014, Taxonomy and phylogeny of Pluteus glaucotinctus sensu lato (Agaricales, Basidiomycota), a multicontinental species complex, Phytotaxa 188 (2), pp. 78-90 : 82-84

Pluteus izurun P. Arrill. & Justo , sp. nov. ( Fig. 3 )

MycoBank: MB 809614

Diagnosis: —Similar to P. meridionalis but differing in the tef1 sequence ( KJ010047 ), presence of distinct blue-green tinges at stipe base, shape of basidiospores, pleurocystidial apex, and length of the pileipellis elements.

Type: — SPAIN. Guipúzcoa : Donostia / San Sebastián, 18 August 2011, leg. P . Arrillaga s.n. (Holotype ARAN-Fungi 3008424-1!; nrITS: JQ065023 ; tef1: KJ 010047 ) .

Pileus 20–52 mm in diam., campanulate when young, expanding to convex or plano-convex, with a broad obtuse umbo that becomes depressed at center with age; surface of young specimens white and smooth except at center, which is set with olivaceous (2.5 Y 6/6, 6/8, 7/6, 7/8) to dark gray or bluish gray (in the range of Gley2 4/1, 5/1, 6/1) squamules and fibrils, becoming entirely fibrillose in older specimens; dry or slightly viscid when moist, slightly hygrophanous; margin translucent-striate up to 1/3 of the pileus. Lamellae crowded, free, ventricose, up to 7 mm broad; white when young, later pink (7.5 R 8/4); with white, flocculose edges. Stipe 35–70 × 2–4 mm, cylindrical, with a slightly broadened base; surface white, with distinct blue or blue-green tinges at base, smooth or with longitudinal gray-brown fibrils especially near the base. Context in stipe and pileus white, in some places with slight blue-green tinges. Odor indistinct. Taste indistinct or slightly sweet. Spore print pinkish-brown (2.5 YR 7/6–7/8). Basidiospores [84/2/2] (6.0–)6.5–9.0(–9.5) × (5.0–)5.3–7.0(–7.3) μm ( Q = 1.12–1.42; Qm = 1.24; Lm = 7.7 μm; Wm = 6.2 μm), broadly ellipsoid to ellipsoid, rarely subglobose, inamyloid, hyaline, smooth, thick-walled. Basidia 23–36 × 8.0–18 μm, four-spored, clavate or narrowly utriform. Pleurocystidia (50–)55–85 × 13.0–28 μm; ovoid, conical or narrowly utriform with rounded apices, colorless, thin-walled; scattered to relatively common all over lamellar sides. Lamellar edge sterile. Cheilocystidia 35–60(–70) × 12.0–25 μm; narrowly lageniform to narrowly utriform, sometimes mucronate, apices usually with a short and narrow papilla, colorless, thin-walled; crowded, forming a well-developed strip. Pileipellis a cutis; individual terminal elements 55–225(–380) × 5.0–18.0(–23) μm, cylindrical or fusiform, colorless or with blue-green intracellular pigment in fresh specimens, turning brown on drying, additional parietal pigment sometimes present; thin-walled. Stipitipellis a cutis; hyphae 3.5–7.5(–10.0) μm wide; apex with distinct terminal elements 75–138 × 12.0–16.0 μm; narrowly clavate to fusiform, colorless or with flexuous hyphae filled with blue-green or greyish pigment at base, thin-walled. Clamp connections absent.

Etymology: — izurun is the earliest recorded name given to the place that would later become Donostia/San Sebastián. We choose to use the more euphonic noun form “izurun” instead of the adjectival “izurunensis”.

Habit, habitat and distribution: —Gregarious, in pairs or subgregarious up to three basidiomata. A total of 10 basidiomata was collected in four independent consecutive fruitings on the same well-decayed (brown-rot) log of Quercus sp. between mid-August and mid-September in an urban park. Europe: Known only from Northern Spain.

Additional specimens examined: — SPAIN. Guipúzcoa : Donostia / San Sebastián, 1 September 2011, leg. P . Arrillaga s.n. (ARAN-Fungi 3008424-2!; nrITS: JQ065024 , tef1: KJ 010048 ) ; ibid. 3 September 2001, leg. P. Arrillaga s.n. (ARAN-Fungi 3008424-3!) ; ibid. 11 September 2011, leg. P. Arrillaga s.n. (ARAN-Fungi 3008424-4!) .

Notes: — Pluteus izurun is characterized by a stipe with distinct blue or blue-green tinges at base, broadly ellipsoid to ellipsoid or rarely subglobose basidiospores (Qm = 1.24), pleurocystidia with rounded apices, cheilocystidia usually with a short and narrow papilla at the apices, and long pileipellis elements (up to 380 μm long). Pluteus glaucotinctus differs in the slightly more elongate basidiospores (Qm = 1.33), the slightly pigmented cheilocystidia with no apical appendage, and in the significantly shorter pileipellis elements (up to 90 μm long). Pluteus meridionalis lacks distinct blue-green tinges on the stipe, has more elongate basidiospores (Qm = 1.40), and their pleurocystidia have a truncate apex or minor apical and lateral projections. Pluteus padanilus differs in the pleurocystidia that have truncate to subcapitate apices or indistinct 2–3 short apical projections and that sometimes are provided with internal septa and/or incrusting parietal pigment at the apex. Pluteus thoenii has predominantly subglobose basidiospores (Qm = 1.15) and longer cheilocystidia (up to 94 μm).

Considering the tropical distribution of P. glaucotinctus , P. meridionalis , P. padanilus and P. thoenii , the occurrence of P. izurun in the Iberian Peninsula seems to be exceptional. When compared to these species, the fruiting pattern of P. izurun in Spain could be explained tentatively by the climatological condition during the collecting period. Data from the nearest climatologic station (Oiartzun Observatory, located less than 10 km away from the collecting site) indicate that between mid-August and mid-September 2011 the daily average temperatures were between 17ºC and 26ºC and the relative humidity was between 70% and 97%, which are similar to the conditions found in tropical areas.

The habitat observed in P. izurun is also worthy of comment. The fruiting on a brown-rotted log is particularly noteworthy as the habitat is atypical for Pluteus , which is usually found on white-rotted wood or more rarely on other organic debris. Wood that has undergone brown-rot decay is deprived of most of its cellulosic components while the lignin remains mostly intact, thus providing limited nutrients for fungal species ( Yelle et al. 2008; Martinez et al. 2009). While it is very unlikely that P. izurun was responsible for the brown-rot decay observed in the substrate, it is interesting that this fungus is not only able to survive in such a nutrient-poor environment but that it is also able to produce basidiomata many times in less than a month. No other fungal basidiomata were observed on the same log where P. izurun was growing, but that does not exclude the fact that other fungi were present at the same time or before the arrival of P. izurun .

Figures

FIGURE 3. Pluteus izurun. a–d. Basidiomata. e. Pileipellis elements in Congo Red. f. Basidiospores. g. Basidia. h. Pleurocystidia. i. Cheilocystidia. j. Pileipellis elements. a. ARAN-Fungi 3008424-3. b. ARAN-Fungi 3008424-4. c, e, f–j. ARAN-Fungi 3008424-1 (holotype). d. ARAN-Fungi 3008424-2. Scale bars: a–d = 1 cm. e–j = 10 μm. Photos a–e by P.Arrillaga, line drawings f–j by A. Justo.