Leucocoprinus brunneosporus B.E. Lechner & J.M. Suarez, 2021

Suarez, Juan M., Gottlieb, Alexandra M. & Lechner, Bernardo E., 2021, A new and intriguing brown-spored Leucocoprinus species, Phytotaxa 479 (1), pp. 44-54 : 48-50

Leucocoprinus brunneosporus B.E. Lechner & J.M. Suarez , sp. nov. Figure 3 , 4

MycoBank MB 836431

Etymology—from the Latin “brunneo-” and “sporus”, in reference to the brown colour of the spores.

Holotype — ARGENTINA, Buenos Aires: Lomas de Zamora, Reserva Histórica de Santa Catalina, Instituto Fitotécnico de Santa Catalina , 30º03’56.9” S, 51º7’28.9” W, 9 Aug 2017, Leg. Suarez & Lechner, BAFC 53417 .

Diagnosis— Leucocoprinus brunneosporus is macromorphologically similar to Lc. birnbaumii , but the spores are brown in KOH and pseudoparaphyses are absent.

Basidiomata ( Fig. 3 A-C, 4A) small to medium-sized. Habit lepiotoid. Pileus 20–50 mm diam., initially ellipsoid, becoming convex, broadly convex to campanulate, sometimes broadly umbonate with a pale yellow (2A3) patch; surface yellowish white (2A2), when very young completely floccose-cottony, with minute squamules that are cottony textured, more concentrated towards the center and sparser towards the margin, distinctly striate towards margin; margin initially incurved, later straight, entire or slightly eroded in some specimens. Lamellae free, narrow, crowded, yellowish, becoming pinkish and chestnut when mature, without collarium, without lamellulae; edge fimbriate under a lens. Stipe 30–50 × 3–5 mm, central, terete, tapered from base to apex, becoming hollow, cartilaginous, fistulose; surface sulphur yellow, fibrillose. Annulus superior, membranous, movable, whitish. Context very thin, white. Odour not distinctive. Spore-print light brown (7D4).

Spores ( Fig. 3D , 4B ) 4.2–5.7 × 3.1–4.2 (5.2 ± 0.4 × 3.6 ± 0.3) μm, Q = 1.25–1.67, Qav = 1.47, n= 30, ellipsoidal, with a distinct, narrow germ pore, thin-walled (<1 μm), smooth, metachromatic in Cresyl blue, yellow-brown in KOH, dextrinoid. Basidia ( Fig. 4C ) 11.4–15.1 × 5.2–7.3 μm, clavate, hyaline, with 4 up to 2 μm long sterigmata. Cheilocystidia ( Fig. 4D ) in fascicles making the lamella edge fimbriate, 23.4–32.8 × 11.4–15.1 μm, ventricose-rostrate, pyriform, clavate, inflated clavate, hyaline, thin-walled. Pleurocystidia absent. Pseudoparaphyses absent. Lamella trama parallel; hyphae 2.6–4.7 μm wide, hyaline, thin-walled, inamyloid. Pileal trama interwoven; composed of 5.2–7.8 μm wide, hyaline, thin-walled, cylindrical, inamyloid hyphae. Pileus covering ( Fig. 4E ) a confluent layer of terminal cells when young, disarticulating into scales and/or patches revealing short, inflated to cylindrical, loosely attached H-, Y-, T- to L-shaped cells, on top of a cutis composed of cylindrical 3.1–5.2 μm wide hyphae. Stipe covering a cutis of 5.2–6.2 μm wide, thin-walled, hyaline cells. Clamp connections absent.

Habitat—On soil, humus, gregarious, found under Ligustrum lucidum trees, occasionally close to Hedera helix .

Comments— Lc. brunneosporus is characterized by its pale-yellow colour, the convex to campanulate pileus, which is distinctly striate towards margin, with minute squamules that are cottony textured. The colour of the lamellae is similar to that of the surface of the pileus when it is young, becoming chestnut when mature. Micromorphologically it is characterized by small, weakly dextrinoid spores, absence of pseudoparaphyses, and a pileus covering with scales and/or patches with short, inflated to cylindrical, loosely attached H-, Y-, T- to L-shaped cells.

Lc. brunneosporus is macromorphologically very similar to Lc. birnbaumii and Lc. straminellus but is easily distinguishable by its light chestnut-coloured lamellae at maturity, a thinner flesh of the pileus and the absence of lamellulae. Regarding the micromorphological characters, Lc. brunneosporus differs from these species by their smaller, coloured spores, smaller and clavate basidia, absence of pseudoparaphyses, and cheilocystidia appearing in fascicules. Leucocoprinus fragilissimus has a very thin-fleshed pileus and lacks pseudoparaphyses, just like Lc. brunneosporus , but the former species shows the same differences highlighted previously for Lc. birmbaumii and Lc. straminellus , and has a very thin-fleshed pileus and a long slender stipe. In general, the spores of Lc. brunneosporus are smaller than those of most of the species of the genus, but similar to the spores of Lc. flavescens (Morgan) H.V. Sm. , which has spores 4.4–5.1–5.9 × 3.6–4.1–4.8 μm, Q-value 1.00–1.27–1.42, hyaline in KOH, according to Birkebak (2010). Moreover, Lc. flavescens has a lighter-coloured pileus compared to Lc. brunneosporus .

Additional material examined— Argentina, Buenos Aires, Lomas de Zamora, Reserva Histórica de Santa Catalina, Instituto Fitotécnico de Santa Catalina , 10-IX-2017, collector: J. M . Suarez, BAFC 53418 ; ibidem, 11-IX-2017, collector: J. M . Suarez, BAFC 53419 .

Figures

FIGURE 3. Leucocoprinus brunneosporus. A-C: Different views of the collected materials (BAFC 53418); D: photograph of spores on water. Scale bar: = 20 mm for A-C, 4 µm for D.

FIGURE 4. Macro- and micromorphology of Leucocoprinus brunneosporus. Collection BAFC 53417 (holotype). A: Basidiomata; B: Basidiospores; C: Basidia; D: Cheilocystidia; E: Pileus covering elements. Scale bar: 15 mm for A, 6 µm for B, and 20 µm for C–E.