Romagnesiella clavus (Romagn.) Contu, Matheny, P.-A. Moreau, Vizzini & A. de Haan, in Matheny, Moreau, Vizzini, Harrower, De Haan, Contu & Curti, Syst. Biodiv. 13(1): 36 (2014)
Pileus 5–9 (12) mm diam, hemispheric-umbonate then ± depressed around umbo, margin early inrolled becoming shortly crenulate when old, even, not striate, densely furfuraceous- micaceous, grey-brown with somewhat purplish tones when fresh, paler at margin, quickly fading from margin to uniformly fleshy-ochre, without any trace of veil. Lamellae adnexed-ventricose at first, becoming shortly uncinate in age, distant with 14–16 L reaching stipe, interspersed by 12 series of lamellulae, dull rusty ochre even when young; edges smooth but (sub)sterile, pale yellow. Stipe 15–25 x 1 mm, flexuose, slightly attenuate at base and inflated at apex, pruinose-floccose just below lamellae, fibrillose below then glabrous against a uniform dirty brown ground colour, slightly purplish when young; no perceptible trace of veil (primordia not observed). Context dark brown when fresh, pale ochre when dry. Odour and taste fungoid, not remarkable.
Basidiospores (5.6) 6.2–6.7–7.3 (8.5) x (3.6) 3.9–4.2–4.4 (5.0) µm, Q = 1.51–1.62–1.73 (n = 48), ovate to obovate but longer spores more fusiform, smooth, germ pore absent; bright yellow in water, amber yellow in Melzer’s, warm reddish ochre in KOH, wall thickened up to 0.3 (0.5) µm; content with a large central droplet, often elongate. Basidia four-spored, 28–36 x 7–9 µm, broadly clavate, with long sterigmata, content often microguttulate; necrobasidia abundant, with reddish-brown content. Cheilocystidia 22–45 x 5.5–7 µm, cylindrical-flexuose with slightly thickened yellowish wall, mixed with fascicles of terminal hyphae issued from trama with pear shaped to subglobose terminal cells, 9–14 mm wide, lamella edge fertile to locally substerile. Pleurocystidia 38–42 x 7.5–13 µm, cylindrical to subutriform, not very distinct but not rare. Hymenophoral trama regular, with strongly encrusted hyphae, 3–5 µm wide. Pileipellis a superficial layer of short cells, these lobate, digitate, puzzle-like, fusiform or pyriform, 12–16 µm wide, more or less erected to nearly hymeniform towards margin, pale in KOH, smooth, issued from hyphae of subpellis; subpellis filamentous, coarsely encrusted, thick-walled, deep yellow to reddish brown in KOH, continuous with pileus context. Stipitipellis a cutis with sparse to fasciculate (at apex) caulocystidia measuring 16–25 x 5–12 µm, cylindrical to clavate-pyriform, very rare below apex; superficial hyphae slender, 2–3.5 µm wide. Clamp connections frequent.
Habitat and distribution: Often on calcareous, mineral- rich, sandy or alluvial substrates in pioneer or disturbed habitats including fixed coastal dunes and banks of trails or paths among mosses and grasses. Less frequent in secondarized dunes, scattered and never abundant. Europe (Belgium, France, Switzerland) and reported from Italy, the Netherlands, and North Africa. Fruiting Sept.–Nov.
Index Fungorum number: IF519560
Notes: The interpretation of Galerina clavus is based on the detailed protologue of Romagnesi (1944 ), which matches collections from Belgium and Switzerland. Unfortunately, no original material of Galerina clavus exists. The herbarium packet corresponding to one of the two collections cited by Romagnesi (1942: 145) Yerres, bois de Cer¸cay, 18 Jun 1942, kept in herb. H. Romagnesi (PC) was empty. The other cannot be located. Because a figure that depicts G. clavus exists in the protologue, this must serve as the lectotype. Original drawings of G. clavus made by Romagnesi also exist at PC. Thus, PAM06090110 (LIP) was designated as an epitype.
The species features some morphological and microscopic variation. The epitype (sequenced here), showed purplish-grey tones on the stipe as well as the pileus, but the protologue only mentions this colour on the stipe. Belgian collections described by de Haan & Walleyn (2009) describe a more convex pileus, broadly adnate instead of subdecurrent lamellae, a ‘weakly farinaceous’ taste, and habitat in dry mineral spots in urban grasslands. However, all collections show gradual variation in the pileus shape, colour and lamellae attachment.
Coastal collections are probably better considered as variants of R. clavus. Despite some variation in spore dimensions, any support for specific or infraspecific distinctions could not be found. Detailed spore measurements illustrate continuity in these variation patterns but apparent differences.
North African and Sardinian collections of Galerina clavus, as described by Hausknecht & Zuccherelli (1993) and Malen¸con (Moreau, 2009), differ from continental collections by somewhat larger basidiospores [(7.0) 7.6–8.2–9.0 (10) x (4.0) 4.9–5.2–5.5 (5.7) µm, Q = 1.48–1.59–1.70], slightly larger cystidia, and a filamentous pileipellis with a more or less continuous suprapellis of slender cylindrical hyphae with sparse slightly upraised terminal elements. It is possible that Mediterranean collections may represent distinct populations. One collection from Sardinia was sequenced (C15122007, leg. M. Contu), in which the ITS1 region reveals nine site differences with R. clavus PAM6090110, four of which, however, are polymorphic in C15122007. Galerina clavus has also been reported from the Netherlands (www.verspreidingsatlas.nl/046620).
Romagnesiella clavus is probably often confused with other naucorioid species frequent in the same environment, such as Galerina graminea (Velen.) Kühner, Psilocybe pratensis P.D. Orton, or Tubaria spp. The distant lamellae and absence of a veil on the stipe are good distinctive field characters.
Figure 1. Phylogeny of the Agaricoid clade based on a Maximum Likelihood and Bayesian Inference analysis of a supermatrix of four nuclear gene regions (5.8S rRNA, LSU-rRNA, SSU-rRNA and rpb2 conserved domains 57). Thickened branches indicate ML bootstrap support >70% and Bayesian posterior probability >0.95. Nodes that receive Bayesian posterior probabilities >0.95 but with <70% ML bootstrap are indicated by small black-filled circles. Clade nomenclature follows Matheny et al. (2006).
Figure 1. (Continued)
Figure 2. Basidiomes of Romagnesiella clavus in situ (PAM06090110). Photo by P.-A. Moreau. Scale bar = 10 mm