Mycena brunneoviolacea A.C. Cooper, Desjardin & B.A. Perry, 2018

Cooper, Alexandra C., Desjardin, Dennis E. & Perry, Brian A., 2018, The genus Mycena (Basidiomycota, Agaricales, Mycenaceae) and allied genera from Republic of São Tomé and Príncipe, West Africa, Phytotaxa 383 (1), pp. 1-47 : 10-11

1. Mycena brunneoviolacea A.C. Cooper, Desjardin & B.A. Perry , spec. nov. ( Figs. 4 , 5 )

MycoBank no.: MB 825510

Holotype:—AFRICA. São Tomé, Macambrara radio antenna area, elevation 1300 m, N00˚16.557’, E06˚36.326’, 11 April 2008, D.E. Desjardin and B.A. Perry, BAP 594 ( SFSU).

Etymology:— brunneus (L.) = brown, violaceus (L.) = violet – referring to the pileus and stipe colour.

Diagnosis:— Pileus 15–31 mm diam, initially broadly campanulate, becoming broadly convex to planar, margin pellucid–striate or striate, eroding in age; surface moist, glabrous, hygrophanous, disc dark brown (5–6F6–7) or dark violet-brown (9-10F4-5), fading to greyish brown (5–6E4–5) away from disc, pale grey to pale cream-grey, ash-grey or greyish ruby (12C–D3–4) with lilac tones towards the margin. Context thin, concolorous with pileus. Lamellae ascending-adnate to adnexed with a short decurrent tooth, subdistant with 1–2 series of lamellulae, non-intervenose or dorsally weakly intervenose, white to pale cream-grey, pale brownish grey or pale grey; edge entire, concolorous.

Stipe 40–65 × 1.5–2.5 (apex) × 3–5 (base) mm, central, terete or compressed, broadened towards the base, hollow;

surface moist to dry, smooth, glabrous or minutely pruinose, greyish brown (8E-F3-4) to brownish grey (4–5D–E4) or pale grey with hints of greyish ruby (12C–D3–4), base with white tomentum. Odour indistinct; taste not determined.

Bioluminescence undetected.

Basidiospores 5.6–8.0 × 3.2–4.8 μm [x mr = 6.5–7.3 × 3.8–4.4 μm, x mm = 6.93 ± 0.6 × 3.88 ± 0.1 μm, Q = 1.3–2.3, Q mr = 1.73–1.86, Q mm = 1.80 ± 0.1, n = 20, s = 2], ellipsoid to oblong, smooth, hyaline, amyloid, thin-walled. Basidia 17.6–25 × 4.8–6.4 μm, clavate, hyaline, inamyloid, thin-walled, 4-spored, sterigmata up to 6.4 μm long. Basidioles clavate. Cheilocystidia 32–72 × 9.6–18.4 μm, narrowly lageniform to lageniform, occasionally fusiform-strangulate,

hyaline, inamyloid, thin-walled. Pleurocystidia common, similar to cheilocystidia. Pileipellis a cutis; hyphae 2–8 μm diam, repent, cylindrical, non-diverticulate, hyaline, inamyloid, thin-walled, non-gelatinous. Hypodermium composed of inflated cells up to 38 μm diam, globose to ovoid, smooth, hyaline, dextrinoid, thin-walled; interspersed with numerous laticiferous hyphae up to 4.0 μm diam with knob-like projections. Lamellar trama regular; hyphae 2.5– 19 μm diam, hyaline, dextrinoid, non-gelatinous, thin-walled; interspersed with numerous laticiferous hyphae up to 3.2 μm diam with knob-like projections. Stipitipellis a cutis; cortical hyphae 4.0–8.0 μm diam, parallel, cylindrical, hyaline, dextrinoid, thin-walled, non-gelatinous; medullary hyphae 6.4–12.0 μm diam, smooth, dextrinoid, thin-walled; interspersed with numerous laticiferous hyphae up to 8.0 μm diam with knob-like projections. Caulocystidia rare or scattered, 36–80 × 4.8–10.4 μm, subcylindrical to fusoid, hyaline, inamyloid, thin-walled. Clamp connections present in all tissues.

Habitat and known distribution:—Gregarious and cespitose on decaying wood in upland forest. ( São Tomé).

Additional material examined:—AFRICA. São Tomé, Macambrara radio antenna area, elevation 1300 m, N00˚16.557’, E06˚36.326’, 25 April 2008, D.E. Desjardin and B.A. Perry, BAP 656 (SFSU).

Notes:— Mycena brunneoviolacea is distinguished by medium-sized basidiomata with greyish brown to violet-brown, striate pileus, white to pale grey lamellae, a glabrous to minutely pruinose, hollow, brownish grey stipe with a hint of greyish ruby, an indistinct odour, ellipsoid basidiospores with mean 6.9 × 3.9 μm, lageniform to fusiform-strangulate hymenial cystidia and caulocystidia, a cutis-type pileipellis of non-diverticulate hyphae, and growth on decayed wood. In combination, these features indicate placement in sect. Calodontes .

Pairwise comparisons of aligned, overlapping ITS sequences of M. brunneoviolacea (BAP 594) with the top ten BLAST results show 94.5–95.4% similarity to several north temperate species of sect. Calodontes ( M. diosma Krieglst. & Schwöbel , M. pura (Pers.) P. Kumm. ), and 88.4–95.1% similarity to several Malaysian species of sect. Calodontes ( M. cahaya A.L.C. Chew & Desjardin , M. sinar A.L.C. Chew & Desjardin , M. seminau A.L.C. Chew & Desjardin ). As reported above, the closest similarity to M. brunneoviolacea within sequenced members of sect. Calodontes is 95.4% (>4.5% difference). In a three-gene phylogeny of the Mycena pura complex, Harder et al. (2013) reported that a 1.5–3% ITS sequence difference threshold level underestimated diversity within the group.

Mycena brunneoviolacea is morphologically similar to the Malaysian species noted above, which all differ in forming bioluminescent basidiomata with white or beige stipes and growth on decomposing leaves. In addition, M. seminau and M. sinar lack pleurocystidia. Mycena griseoviolacea Métrod , described from Madagascar ( Métrod 1949), differs in forming much broader basidiospores (5.5–5.7μm) and longer hymenial cystidia (80–120 μm). Two lignicolous species described from Australia, viz., M. clarkeana Grgur. and M. subcorticalis Grgur. , differ in basidiomata coloration (reddish brown to brick red) and larger basidiospores (means 9.9–10 × 6.3–6.7 μm) ( Grgurinovic 2003). Based on a combination of morphological and available molecular data, we recognize the São Tomé taxon as a distinct species. In the ITS phylogeny ( Fig. 2), M. brunneoviolacea falls into the sect. Calodontes clade, sister to M. pearsoniana Dennis ex Singer.

Figures

FIGURE 4. Basidiomata of Mycena brunneoviolacea (BAP 594, Holotype). Scale bar = 10 mm.

FIGURE 5. Mycena brunneoviolacea (BAP 594,Holotype).a.Basidiospores.b.Basidia and basidiole.c. Cheilocystidiaand pleurocystidia. d. Caulocystidia. Scale bar = 10 μm.