Gerhardtia citrinolobata Angelini & Vizzini, 2017

Vizzini, Alfredo, Angelini, Claudio & Ercole, Enrico, 2017, Is the species diversity in the lyophylloid genera Calocybella and Gerhardtia (Agaricales, Basidiomycota) underestimated? Two new species from the Dominican Republic, Phytotaxa 291 (4), pp. 241-252 : 247-249

Gerhardtia citrinolobata Angelini & Vizzini , sp. nov. ( Figs. 6–8 )

Mycobank MB819495

Diagnosis: — Distinguished by a lemon yellow, applanate, 12–25 mm broad pileus with an ochraceous brown obtuse umbo and an irregular to plurilobate, shortly translucent-striate margin; adnate-emarginate to shortly decurrent, whitish lamellae; a white, pruinose stipe; strong, mealy odour and taste; ellipsoid, inamyloid, cyanophilous basidiospores (4.0–) 4.1–5.0 (–5.1) × (2.5–) 2.9–3.4 (–3.5) μm (on average 4.69 × 3.03 μm), with a mostly ± undulate, Rhodocybe -like surface; a cutis-type, slightly gelatinised pileipellis; clampless hyphae, and unique nrLSU and nrITS sequences.

Type:— THE DOMINICAN REPUBLIC. Puerto Plata, Sosúa, Loc. Playa, on man-made litter in a deciduous forest, understory composed of Petivera alliacea (Anamù), 10 December 2013, C. Angelini , JBSD 126508 , holotype ( JBSD!) ; AH 46063 , isotype ( AH!) .

Etymology:—The epithet derives from the Latin words citrinus (yellow) and lobatus (lobed) and refers to the colour and margin shape of the pileus.

Description:— Basidiomes small, collybioid. Pileus 12–25 mm broad, at first plano-convex, soon becoming expanded, with a broad obtuse umbo, sometimes with depressed to subumbilicate centre; margin thin, shortly translucent-striate, irregular, wavy, undulating, strongly and deeply pluri-lobed (petaloid, reminiscent of the petals of a flower); surface smooth but slightly wrinkled at centre, shiny, greasy, slightly hygrophanous, lemon yellow (Maize Yellow, Pinard Yellow, Picric Yellow, Pale Lemon Yellow, Plate IV) with evident greenish hues, darker, ochraceous brown (Mars Yellow, Plate III; Yellow Ocher, Ochraceous-Tawny, Plate XV) at centre, paler, whitish at margin. Lamellae white, close, adnate-emarginate to shortly decurrent, 1.5–2 mm broad; lamellulae l = (0) 1–4 (5); edge slightly eroded and concolorous. Stipe 16–21 × 2–4 mm, cylindrical, equal or slightly inflated towards the base, straight or curved towards the base, firm, whitish, white-pruinose overall, fibrillose; base subtended by abundant and thin whitish rhizoids; surface not or only slightly changing to red on bruising. Context thin at pileus centre, whitish, fibrous, elastic. Odour and taste strongly mealy. Spore print not obtained.

Basidiospores (4.0–) 4.1–5.0 (–5.1) × (2.5–) 2.9–3.4 (–3.5) μm [40/1/1], on average 4.69 × 3.03 μm, Q = (1.33–) 1.36–1.7 (–1.8), Qm = 1.54, often released in tetrads, triads or dyads (pairs), ellipsoid, hyaline, thin-walled, surface (outline) mostly ± undulate (somewhat reminiscent of some Rhodocybe spores seen in profile view), monoguttulate, inamyloid, cyanophilous. Basidia 18–21 × 5.0–7.0 μm, clavate, hyaline, siderophilous, 2- and 4-spored; sterigmata up to 3.0 μm long. Hymenial cystidia absent. Hymenophoral trama regular, consisting of parallel, 5–6 μm wide hyphae. Pileipellis as an ixocutis (slightly gelatinised) composed by parallel hyphae up to 6.5 μm wide, with some repent hyphae ending with a clavate, up to 33 × 5.0 μm element; with parietal and cytoplasmatic light yellowish-ochre pigmentation. Stipitipellis similar to the pileipellis but not gelatinised, with up to 3.5 μm wide hyphae; irregular, up to 40–50 μm long and sometimes repent caulocystidioid hyphae are present along the stipe surface. Stipititrama regular consisting of parallel, up to 6.5 μm wide hyphae. Clamp-connections absent on all hyphae.

Habit, habitat and distribution: — Basidiomes collybioid, gregarious in small groups, on wet deciduous forest litter, in rainy periods. So far, this species has been found in the winter period (December) in the coastal area around Sosúa-Puerto Plata, in a forest consisting mainly of the following tree species Bucida buceras L., Guazuma tomentosa H.B.K., Hura crepitans L., Swietenia mahagoni (L.) Jacq., Terminalia catappa L.), Samanea saman (Jacq.) Merrill , Ocotea coriacea (Sw.) Britton , Bursera simaruba (L.) Sarg., Celtis trinervia Lam. , Tabebuia rosea (Bertol.) DC. Shrubby undergrowth consisting mainly of “Anamu” (Petivera alliacea L.).

Notes:— Gerhardtia citrinolobata is strikingly distinct from all the other Gerhardtia species described so far ( Bon 1999; Contu & Consiglio 2004; Cooper 2014). Its collybioid habit, the yellow-green pileus with a strongly wavy and lobate margin, the ochraceous brown umbo, the white lamellae, the mealy odour and taste, and the small, slightly undulate, up to 5 μm long basidiospores, are diagnostic characters. Considering the Gerhardtia species for which DNA sequences are available ( Figs. 1–2 ), G. borealis ( Fries 1838: 44) Contu & A. Ortega (2002: 176) [= G. incarnatobrunnea ( Gerhardt 1982: 241) Bon (1994: 66) ], the type species of the genus and so far known only from Europe, differs by the tricholomatoid habit, a brown-orange, 40–90 mm broad pileus, a thicker stipe (× 8–15 mm), 2–8 mm broad lamellae, and longer basidiospores (4.5–6.5 × 2.5–3.5 μm) ( Gerhardt 1982; Riva 1987; Gulden 1993; Carbó & Pérez-de-Gregorio1999; Bon 1999; Contu & Consiglio 2004; Kalamees 2004, 2012b). Gerhardtia highlandensis (Hesler & A.H. Smith 1943: 254) Consiglio & Contu (2004: 158) from North America possesses a tricholomatoid habit, a 25–100 mm broad pileus, whitish or pinkish cinnamon on centre, subdistant, 2–9 mm broad lamellae, 30–90 × 5–15 mm stipe somewhat inflated at the base (× 12–25 mm), and a fragrant but not well-defined odour ( Smith & Hesler 1943; Bigelow 1985). Gerhardtia pseudosaponacea J.A. Cooper & P. Leonard in Cooper (2014: 269) from New Zealand, shows a tricholomatoid habit, straw to buff pileus, a hymenodermic pileipellis (presence of inflated elements), and smooth ± undulate basidiospores ( Cooper 2014; Vizzini et al. 2015).

Among the Gerhardtia species not yet sequenced, the morphologically closest are G. marasmioides (Singer in Singer & Digilio 1952: 424) Consiglio & Contu (2004: 159) from Argentina which differs by an ochraceous pileus, distant lamellae and even narrower basidiospores (× 2.7 μm) ( Singer & Digilio 1952; Baroni 1981; Contu & Consiglio 2004); G. suburens ( Clémençon 1968: 420) Consiglio & Contu (2004: 159) from North America, is characterised by a greyish wax yellow pileus with a strongly recurved margin at first, lamellae concolorous to the pileus, a strong Lycoperdon -like odour, a taste mild at first but sharply acrid after about 30 seconds, and oblong, 6–7.5 × 2–2.5 μm, basidiospores ( Clémençon 1968; Bigelow 1985).

Figures

FIGURE 1. Bayesian phylogenetic analysis based on the nrLSU sequences of Lyophyllaceae. BPP values (in bold) ≥ 0.7 and MLB values ≥ 50 % are shown on the branches. For each sequenced taxon the Genbank number is given. The newly sequenced collections are in bold.

FIGURE 2. Bayesian phylogenetic analysis based on selected nrITS sequences of Lyophyllaceae. BPP values (in bold) ≥ 0.7 and MLB values ≥ 50 % are shown on the branches. Thickened branches indicate Bayesian posterior probability ≥ 0.95 and ML bootstrap support ≥ 70 %. For each sequenced taxon the Genbank/UNITE number is given. Newly sequenced collections are in bold.

FIGURE 6. Gerhardtia citrinolobata. Fresh basidiomes (holotype, JBSD 126508). Scale bar: 10 mm. Picture by C. Angelini.

FIGURE 7. Gerhardtia citrinolobata. Microscopic features (holotype). a Stipitipellis and repent hyphae b–c Basidiospores d Pileipellis e Basidiospores released in tetrads and dyads f Hymenium. a–b, d–f (in ammoniacal Congo Red); c (phase contrast microscopy). Scale bars: a = 10μm; b–c = 3μm; d = 8μm; e = 3.3μm; f = 5μm. Pictures by C. Angelini.

FIGURE 8. Gerhardtia citrinolobata. Basidiospores (isotype, AH 46063). Bars = 1 μm. Scanning electron micrographs by G. Moreno.