Coltricia insularis P.-A. Moreau, Bellanger, Loizides & A. Rinaldi, sp. nov.
Index Fungorum number IF 900072; MycoBank number: MB 900072; Faceoffungi number FoF13395; Fig. 1
Etymology – Insularis = of islands, a Latin adjective referring to Corsica, Cyprus and Sardinia, three Mediterranean islands in which the species was discovered.
Holotype – LIP 0401817
Pileus 15–60 mm, irregularly infundibuliform, rough, sometimes weakly lobed, subtomentose or more distinctly tomentose to subhirsute towards the centre, radially corrugated or furrowed and usually with well-defined concentric chromatic zones; colours ranging from brown, red-brown, grey-brown, purple, umber or ochraceous; margin often paler and somewhat undulating. Hymenial surface poroid, comprised of adnexed to irregularly decurrent, shallow, angular, or somewhat elongated pores, mostly 2–3 per mm, becoming poorly defined towards the margin and sometimes fusing to form sterile tomentose patches or a sterile marginal zone; warm grey to buff or ochraceous. Stipe 20–40×3–8 mm, usually irregularly furrowed, densely tomentose, buff or pale brown at the apex but quickly staining ochraceous or brown, darker chestnut to red-brown or orange-brown lower, deeply submerged into the substrate and often with sand and litter tightly adhered to it. Context corky, thick and indistinctly zonate in the pileus, darker in the stipe, chestnut to redbrown or umber.
Spores (6.8) 7.5–9 (10.2) ×3.2–3.9 (4.1) µm, ellipsoid to broadly ellipsoid or ovoid when immature, cylindrical to fusiform when projected, with a light supra-apicular depression, pale yellow in KOH and in Melzer’s, wall <0.3 µm thick, smooth. Basidia 12–19 ×7–7.5 µm, 4-spored (partly 2-spored on immature specimens) with spindle-shaped straight sterigmata, shortly cylindrical, hyaline. Hymenophoral setae absent. Edges sterile, made of bunches of slender thin-walled hairs 2.3–3 µm wide, encrusted with yellowish granular deposits. Pileipellis 60–80 µm-thick, convoluted trichocutis, made of generative hyphae 3.5–6(7) µm wide, terminal elements 45–80 µm long, branching often with right-angled furcations, rounded to mucronate at the apex. Stipitipellis a trichocutis made of flexuose, mostly unbranched skeletoid hairs, 70–180 ×3.5–5.5 µm, with occasional secondary septa; wall smooth or with few hyaline mucoid deposits towards the apex, 0.8–1.2 µm thick, yellow in 5% KOH; apex rounded. Clamps absent from all observed septa. Smell weak, faintly acidic.
Habitat and Distribution – Associated with Cistaceae (Cistus spp., Halimium halimifolium) shrubs in dry, sandy places. So far collected from Cyprus, France (Corsica), Italy (Sardinia) and Spain (Andalucia), but probably widespread in xerothermic localities throughout the Mediterranean basin.
Material examined – France: Corsica (Haute-Corse), Monaccia d’Aullène, Réserve naturelle du Mucchiu Biancu, 25 Nov. 2006, D. Borgarino, L. Hugot, C. Lavoise, P.-A. Moreau & F. Richard, PAM06112616 (LIP 0401817, holotype).
Other material examined – Cyprus: Trimiklini, M. Loizides, 28 Feb. 2019, ML91292CO (LIP 0401819).
Italy: Sardinia, Gonnesa, A. Rinaldi, 5 Dec. 2019, Hal-BP-135, LIP 0401740. Spain: Andalucia, Huelva, Almonaster-laReal, under Pinus halepensis and Cistus monspeliensis in a semi-open heathland, A. Gasch Illescas & P.-A. Moreau, 28 Dec. 2019, PAM1912814 (LIP 0401740).
Notes – Coltricia insularis is a xerophilic Mediterranean species characteristic of Cistaceae shrublands, found especially among sands, where it may grow in dense clusters adhered to the bases of rockroses. Also known from the thermo-mediterranean zone in Cyprus and the supramediterranean zone in Andalucia, where a slenderer form of this species was collected on sandy ground, at the edge of a pine forest. In Sardinia, it occurs in pure Halimium stands in coastal areas. However, in places where more potential hosts are present, it might be part of the extensive ectomycorrhizal networks that are common in several Mediterranean ecological settings (Taudiere et al. 2015; Leonardi et al. 2020). From what is known about Coltricia mycorrhizal biology, members of the genus appear to establish ectomycorrhizal associations with a range of hosts (Rinaldi et al. 2008). Coltricia insularis phylogenetically belongs to the group of Coltricia perennis, which has not been the object of monographic revision since the advent of DNA studies. The phylogenetic analysis (Fig. 2) shows the unexpected diversity unravelled in this lineage, in which at least three main subclades can be identified among the available sequences in GenBank and UNITE. Most of these are devoid of Linnaean names and the need of typification of C. perennis itself (type of the genus) is obvious, considering this name has been arbitrarily applied to nearly all sequences available in the’Perennis-clade’. Coltricia montagnei Fr. (in Montagne 1836, p. 341), originally described from Northern France (Ardennes, near Sedan), has been variously interpreted and was only recently described in detail (Rivoire 2020). Coltricia confluens Keizer (1997, p. 389), from which the isotype collection Keizer 93060 was kindly provided by the author, but unfortunately, could not be sequenced. Coltricia insularis differs from all currently recognized European species by spore dimensions and shape: mature specimens display spores with an average Q of around 2.3 and a typical fusiform profile. Like C. perennis and C. confluens (but not C. montagnei), the hyphae of pileipellis are frequently T-branched, but the taxonomic importance of this feature requires further observations. Coltricia’confluens’ and a sister Mexican species (Fig. 147), represent an independent well-supported clade. Amongst the subclade 3 (Fig. 2), C. insularis has an American sister species (sequences ITS MH211968 and MK966429 from pine forests in Oregon); both sequences form a well-supported subclade, distinct from the two other subclades of Clade 3 representing apparently circumboreal North European, North American and Asian species. None of the collections available in these clades suggests a thermophilic or xerophilic Mediterranean origin. A detailed revision of collections representing each clade is required before a thorough comparison of this cluster of species with C. insularis and within the whole “Perennis-clade” can be made.
Figure 1 – Coltricia insularis. a-c Basidiocarps. d Basidiospores. e, f Pileipellis. g Hymenial trama, longitudinal section. h Stipitipellis. All from LIP 0,401,817 (holotype, pictures by D. Borgarino (b) and P.-A. Moreau) except a (Hal-BP-72, sequence MT594499, picture by A. Rinaldi) and c (Hal-BP-19, sequence MT594498, picture by A. Rinaldi). Scale bars=5 mm (a-c), 10 µm (d-g)
Figure 2 – Phylogenetic analyses were conducted online at www.phylogeny.fr (Dereeper et al. 2008). Multiple sequence alignments were performed with MUSCLE v. 3.7 (Edgar 2004). Maximum likelihood
(ML) phylogenetic analysis was achieved with PhyML v. 3.0 (Guindon et al. 2010), using the GTR + I +Γ model of evolution and the Shimodaira Hasegawa version of the approximate likelihood-ratio test (SH-aLRT) of branch support (Anisimova et al. 2011). Phylogram was built using TreeDyn 198.3 (Chevenet et al. 2006) and edited with Inkscape 0.91 (https://inkscape.org/fr). Newly generated sequences for this study are in bold. The tree is rooted by mid-point rooting method under PhyML (Guindon et al. 2010)