Xerophorus olivascens (Boud.) Vizzini, Consiglio & M. Marchetti, comb. nov. Figs 10 a–d, 11 a–g
MycoBank number: MB 831418; Index Fungorum number: IF 831418; Facesoffungi number: FoF;
Basionym: Tricholoma olivascens Boud., Bull. Soc. mycol. Fr. 33(1): 7 (1917)
≡ Callistosporium olivascens (Boud.) Bon, Docums Mycol. 6 (22–23): 283 (1976)
= (?) Collybia aerina Quél., Assoc. Franç. Avancem. Sci., Congr. Rouen 1883 12: 498 (1884) [1883]
= (?) Callistosporium olivascens var. aerinum (Quél.) Bon, Docums Mycol. 6 (22–23): 286 (1976)
Description: Habit collybioid. Pileus 15–50 mm broad, first hemispherical to convex, with a narrow involute margin, sometimes with a flattened broad umbo; with age flat-con- vex to flattened, with a straight sinuose-undulate and slightly excedent margin, often a bit depressed at the centre; surface slightly hygrophanous, not translucently striate, dry, minutely tomentose-felted to pruinose, sometimes zonated towards the margin, brown-olive, ochraceous olive, grey-olive, some- times with ochraceous Brick-red tinges, dark grey-brown in the chromatic variant/phenotype by some authors referred to as “C. olivascens var. aerinum (Quél.) Bon” (Bon 1976, 1984, 1991; Perco 1988; Ludwig 2001). Lamellae distant, spaced, L = 15–25, l = 2–5, up to 6 mm broad, ventricose, emarginated to slightly decurrent, Hygrocybe-like (thick and slightly ceraceous), often anastomosing, yellowish to olive yellow, ochraceous-olive or grey-olive; edge entire, con- colorous or somewhat paler. Stipe 18–55 × 2–9 mm, elastic, cylindrical to laterally compressed, often slightly excentric, straight to somewhat curved, flexuose, sinuose, often tapering towards the base, at first fistulose and later hollow; surface dry, fibrillose, at first with a white felt-like covering over an ochraceous background that disappears soon; base with abundant white rhizomorphs incorporating substrate particles. Context thin (< 1.5 mm thick in the centre of the pileus), soft in the pileus but elastic-fibrous in the stipe, cream to yellowish. Smell indistinct or sometimes of rancid flour, taste indistinct or slightly bitter. Spore print whitish.
Macrochemical reactions: the surface of the whole basidioma (both fresh and dried) turns bluish green in basic solutions.
Spores [80, 3, 3] 8.1–10.4 × 4.7–5.7 µm, (on average 9.2 × 5.2 µm), Q = 1.6–1.9 (Qm = 1.70), V = 103–133 µm3 (Vm = 118 µm3), amygdaliform with ogival apex in side view and ellipsoid in front view, hyaline, thin-walled, with an evident apicule, mostly with a big greenish-grey drop, turning green in basic solutions, inamyloid, congophilous, cyanophilous. Basidia 35–60 × 7.0–11 µm, clavate to cylindrical-clavate, tetrasporic, with up to 8 µm long sterigmata, sometimes also bi- or monosporic, and then with sterigmata up to 12 µm long; without basal clamp connections, with a granulose greenish cytoplasmatic content, staining deep green in basic solutions. Subhymenium well differentiated, thick, mostly composed of short elements 3–6 µm wide. Hymenophoral trama composed of regular hyaline hyphae 8–20 µm wide, generally cylindrical but rounded at the septa, with walls up to 0.5(–1.0) µm thick. Cheilocystidia 30–50 × 6–8.5 µm, poorly differentiated, cylindraceous or sometimes flexuose, weakly mucronated, or also subcapitate, smooth, thin-walled, basidiole-like, scattered. Pleurocystidia not observed. Pileipellis a cutis tending to a subtrichoderm of intertwined hyphae 10–20 µm wide, with a smooth greenish cytoplasmatic pigment and an epiparietal greenish yellow pigment (sometimes encrusting in small plates) which turns green-blue with basic solutions, as well as some terminal elements emerging in tufts, cylindrical to flexuose, cylindrical-clavate or subglobose, 14–25(–30) × 4–8(–15) µm, generally smooth. Stipitipellis composed of cylindraceous to rounded at septa or sometimes claviform hyphae 4–12 µm wide and variable in length, with walls up to 1.0 µm thick and epiparietal pigment in small plates. Caulocystidia cylindraceous to clavate, sometimes flexuose, lageniform or bilobed, emerging or repent, with rounded apex or sometimes subcapitate, measuring 30–50(–70) × 4–8(–14) µm. Clamp connections absent.
Ecology: solitary or gregarious, rarely subcaespitose in small clusters, usually under cedars in parks and gardens of southern Europe.
Specimens examined: ITALY: Emilia-Romagna, Ravenna, Bassa del Bardello, meadows, leg. G. Consiglio, M. Caldi- roni & A. Zuccherelli, 18-XI-2010, 18227 (AMB); ibidem, 30-X-2013, 18226 (AMB); Friuli Venezia Giulia, Trieste, Campi Elisi, in a flower bed with cedars, leg. P. Picciola, 25-X-2016, 18229 (AMB); Lombardia, Brescia, in the park in front of S. Anna hospital, numerous specimens, someones fasciculate, in the herb near a cedar, leg. M. Chiari & C. Papetti, 12-XII-1999, 1236/05 EMB; Brescia, in the park of Domus Salutis hospital, leg. C. Papetti, 23-X-2003, 1237/05 EMB; Sardinia, Olbia-Tempio, Aglientu, Rena Majore, on pine wood, leg. G. Consiglio, D. Antonini, M. Antonini & G. Perdisa, 02-XI-2000, 18224 (AMB); Sassari, Alghero, Baratz lake, on pine wood, leg. G. Consiglio, L. Perrone & L. Setti, 03-XI-2008, 18225 (AMB).
Comments: Callistosporium olivascens occurs in south- ern Europe especially under cultivated cedars in anthropic environments, such as gardens and city parks, although its trophic status remains unknown (Boudier 1917; Josserand 1943; Kühner and Romagnesi 1954; Bon 1976, 1984, 1991; Lanzoni 1986; Moser 1986; Bidaud 1988; Perco 1988; Bizio 1991; Courtecuisse 1993; Consiglio and Papetti 2001; Ludwig 2001; Horak 2005; Boccardo et al. 2008; Picciola and Zugna 2017; Tanchaud 2018). Interestingly, it was not reported from the extensive natural forests of Cedrus atlantica at the Moroccan Atlas (Malençon and Bertault 1975). Occasionally, it has been reported to grow among Cupressaceae (Bon 1984; Consiglio and Papetti 2001; Bizio 2012), Pinus spp. (Moser 1986; Picón 2008) and under Cistus (Lavorato 1991), as well as in sand dunes (Picón 1995, 2008; Bizio 2012; Conca et al. 2017). It can be discriminated mainly because of its dark colours, large amygdaliform spores about 8–13 × 5.0–7.0 μm, and more or less cylindrical marginal cystidia (Josserand 1943; Bon 1976, 1984,1991; Moser 1986; Bidaud 1988; Ludwig 2001; Horak 2005; Picciola and Zugna 2017). The specimens sequenced in the present work, both those with typical brown-olive to ochraceous olive pileic colours (e.g. 1236/05 EMB) and those with dark grey-brown tinges (e.g. 18226 AMB, 18227 AMB) proved to be conspecific (Fig. 3), suggesting that “C. olivascens var. aerinum (Quél.) Bon” is only a chromatic form of the type without any taxonomic significance. As a matter of fact, the name Collybia aerina is older (1884) than Tricholoma olivascens (1917) and if their conspecificity were demonstrated in the future, the former must be considered the priority name. The protologue and the drawings of Collybia aerina provided by Quélet (1884) fit well with those of Tricholoma olivascens (Boudier 1917; Josserand 1943; Bon 1984, 1991; Picciola and Zugna 2017) except for the spores which are described as ovoid and depicted (Quélet 1884, plate VI, fig. 2) without the apical papilla so typical in those of T. olivascens.
Fig. 2 50% majority rule ITS rDNA-18S rDNA-28S rDNAtef1-rpb2 consensus phylogram of the family Biannulariaceae (Catathelasma clade) (with Infundibulicybe gibba as outgroup) obtained in MrBayes from 2925 sampled trees. Nodes were annotated if supported by ≥ 0.95 Bayesian PP (left) or ≥ 70% ML BP (right). Nonsignifcant support values are exceptionally represented inside parentheses
Fig. 3 50% majority rule ITS rDNA-18S rDNA-28S rDNA-tef1-rpb2 consensus phylogram of the family Callistosporiaceae (Callistosporium clade) (with Suillus pictus as outgroup) obtained in MrBayes from 27000 sampled trees. Nodes were annotated if supported by ≥ 0.95 Bayesian PP (left) or ≥ 70% ML BP (right). Non-significant sup- port values are exceptionally represented inside parentheses
Fig. 10 Fresh basidiomes of Xerophorus spp. Xerophorus olivascens. a (1236/05 EMB). b (1236/06 EMB). c (18226 AMB). d (18227 AMB). X. donadinii. e (18223 AMB). f (18222 AMB). g (CA20181110.02). X. dominicanus. h (127428 JBSD, holotype). Photographs: a, b by C. Papetti; c, d by G. Consiglio; e, f by M. Maletti; g by C. Agnello; h by C. Angelini
Fig. 11 Microscopical features of Xerophorus spp. Xerophorus oliva- scens. a Pileipellis (pileocystidia, 18224 AMB). b Hymenial elements (18224 AMB). c Cheilocystidia (18227 AMB). d Stipitipellis (cau- locystidia, 18224 AMB). e Spores (18224 AMB). f Spores (18227 AMB). g Spores (18229 AMB). X. donadinii. h Pileipellis (Dona- dini 338-78 LIP, holotype). i Pileipellis (18223 AMB). j Elements of subpellis (18223 AMB). k Hymenial elements (18223 AMB). l Hymenial elements (Donadini 338-78 LIP, holotype). m Hymenial elements and spores (18222 AMB). n Caulocystidia (18223 AMB). o Spores (Donadini 338-78 LIP, (holotype). p Spores (18223 AMB). q Spores (18223 AMB). r Spores (CA 20181110.02). a, c–e, h, k–o, r in ammoniacal Congo red; b, i–j, q in 10% ammonia; f–p in ammoni- acal Congo red-interferential contrast; g in Cotton blue in Lactic acid. Bars = 10 µm. Photographs by M. Marchetti