Pluteus tatafuensis, Del, Jonathan A. & Perry, Brian A., 2025

Del, Jonathan A. & Perry, Brian A., 2025, The genus Pluteus (Basidiomycota, Agaricales, Pluteaceae) from Tafea Province, Republic of Vanuatu, Phytotaxa 709 (1), pp. 1-104 : 94-97

Pluteus tatafuensis J.A. del Rosario & B.A. Perry, sp. nov. ( Figs. 48 , 49 )

MycoBank no:—854229

Holotype:— VANUATU. Tafea Province: Futuna, upper slopes of Mount Tatafu. 19°31.422′S, 170°13.433′E, elev. 485 m, 19 August 2019, coll. J. A. del Rosario & B. A. Perry, JAD 304 ( HAY).

Etymology:—Named in honor of Mount Tatafu on Futuna Island, where the holotype specimen was collected, and the fact that the pileus surface resembles the furrowed flanks of Mount Tatafu.

Diagnosis:— Pluteus tatafuensis from Futuna is characterized by a dark chocolate brown rugose-venose, fuliginous appressed-fibrillose, rimose, marginally sulcate pileus and a white stipe with fuliginous floccules towards the base. Microcharacters include subglobose basidiospores (6.4 × 5.8 µm), broadly clavate cheilocystidia, clavate pleurocystidia sometimes with mucilaginous coating, a transition between a hymeniderm and epithelium pileipellis consisting of globose and lageniform, frequently mucronate brown pigmented cells, fusoid capitate brown pigmented caulocystidia, and an absence of clamp connections.

Description:— Pileus 28 mm diam., convex to hemispherical with a slight centrally depressed umbo, margin sulcate; surface dull, dry, appressed-fibrillose splitting radially in a rimose pattern exposing white context beneath, disc densely rugose-venose; veins dark chocolate brown to black, fibrils fuliginous to pallid brown (oac730–oac732). Context 3 mm thick, white. Lamellae free, crowded with 3+ tiers of lamellulae, thin, dull pinkish brown. Stipe 35 × 3 mm, central, cylindrical over a straight base, hollow; surface dull, dry, silky, minutely flocculose at the base, white to off-white, floccules colored fuliginous to pallid brown, context white. Odor indistinct. Taste indistinct.

Basidiospores (5–) 6–7 × 5–7 µm µm [x m = 6.34 ± 0.55 × 5.84 ± 0.42 µm, Q = 1–1.2, Q m = 1.08 ± 0.08, n = 50, s = 1], globose to subglobose, smooth, hyaline, with a guttule, inamyloid, thick-walled. Basidia 23–30 × 9–10 μm, clavate, 4-spored, hyaline, guttulate, thin-walled, sterigmata 2–4 × 0.5–1 μm. Basidioles 18–24 × 6–11 µm, clavate, hyaline, guttulate, thin-walled. Lamellar edge sterile. Cheilocystidia 30–118 × 11–70 µm, clavate to broadly clavate or sphaeropedunculate to inflated, obtuse, hyaline, thin-walled. Pleurocystidia 43–90 × 14–30 µm, clavate to broadly clavate, obtuse or seldom mucronate, some with apical or completely enveloped in mucilage sometimes with adhering spores that obstruct view, hyaline, thin-walled. Pileipellis a transition between a hymeniderm and epithelium to a euhymeniderm overlaying a subpellis; majority of terminal elements 35–85 × 6–56 µm, globose to broadly clavate or narrowly lageniform to filliform, obtuse, frequently mucronate or rostrate (up to 40 µm long), with brown plasmatic pigment or sometimes hyaline, non-incrusted, non-gelatinous, thin-walled; subpellis a cutis of repent hyphae, composed of hyaline, non-incrusted, non-gelatinous, thin-walled hyphae, 3–8 µm diam.. Pileus trama interwoven, composed of hyaline, non-incrusted, non-gelatinous, thin-walled, cylindrical hyphae, 3–20 µm diam.. Lamellar trama inverse, composed of hyaline, non-gelatinous, thin-walled hyphae 3–12 µm diam.. Stipitipellis a cutis, composed of hyaline, non-incrusted, non-gelatinous, thin-walled hyphae, 3–10 mm diam.. Caulocystidia 35–110 × 5–25 µm, common, solitary to clustered, clavate to cylindro-clavate or narrowly fusoid, some strangulate, infrequently forming trichoderm-like chains, obtuse or capitate, hyaline or pale brown plasmatic pigment, thin-walled. Clamp connections absent in all tissues examined.

Habitat and known distribution:—Solitary on rotted wood in subtropical montane primary cloud broadleaf rainforest containing Atractocarpus sezitat ( Rubiaceae ), Claoxylon psilogyne ( Euphorbiaceae ), Eumachia trichostoma ( Rubiaceae ), Geissois denhamii ( Cunoniaceae ), Ficus septica ( Moraceae ), Neonauclea forsteri ( Rubiaceae ), and Schefflera neoebudica ( Araliaceae ), Vanuatu ( Futuna).

Material examined:— VANUATU. Tafea Province: Futuna, upper slopes of Mount Tatafu. 19°31.422′S, 170°13.433′E, elev. 485 m, 19 August 2019, coll. J. A . del Rosario & B. A . Perry , JAD 304 , ( HAY) .

Notes:—The combination of the rugose-venulose, rimose, marginally sulcate, and fuliginous pileus of P. tatafuensis suggests comparison to a number of similar looking species. The Bolivian P. substigmaticus Singer (1958: 273) produces very similar basidiomes, shares a similarly shaped pileipellis, pleurocystidia and cheilocystidia cells, but differs by the pileus lacking a venose disc and has significantly smaller cheilocystidia and pleurocystidia (15.5–42 × 10.3–16.5 µm equally), which lack mucilage ( Singer 1958). Pluteus rimosoaffinis Singer (1956: 211) , an Argentinean ( Singer 1956) and confirmed Brazilian species ( Pegler 1997, de Meijer 2006; Menolli & Capelari, 2016), has similarly sized and shaped pleurocystidia with apical mucilage, but this species tends to be larger in stature, is not known to have caulocystidia, lacks mucronate or filiform pileipellis elements, and has more utriform non-sphaeropedunculate cheilocystidia. Other similar dark venose species include the tropical American P. jamaicensis Murrill (1911: 278) ( Dennis 1953, Menolli & Capelari 2010, Murrill 1911, Pegler 1983a, Singer 1956, 1958, Singer & Digilio 1952), P. fluminensis Singer (1958: 292) from Brazil, Bolivia and the U.S.A. ( Singer 1958, Menolli et al. 2010), and the Chilean P. fuligineovenosus Horak (1964: 190) ( Horak 1964), but these all differ due to more lageniform non-mucilaginous pleurocystidia, non-sphaeropedunculate cheilocystidia, lack of rostrate and lageniform pileipellis elements, and are phylogenetically distinct.

Phylogenetic analysis of ITS data ( Fig. 37e ) places P. tatafuensis within the romelli / aurantiorugosus clade recognized by Justo et al. (2011b), and sister to an undetermined species of Pluteus from China ( KU382737 , KU382736 ) with strong support ( BS 97 %, PP 0.99). These taxa are placed on a well-supported branch containing additional superficially similar species P. paucicystidiatus Menolli, Justo & Capellari (2015: 1218) , P. stenotrichus Justo, Battistin & Angelini (2012: 17) , P. castaneorugosus E.F. Malysheva & A.V. Alexandrova (2020: 461) , P. iguazuensis Singer (1956: 201) , and an unidentified Pluteus sp. from the Dominican Republic ( KM983705 ). Compared to P. tatafuensis the Brazilian P. paucicystidiatus shares similarly shaped cheilocystidia and pileipellis elements, but these are smaller and the species differs by not having (or only sometimes) pleurocystidia, differently shaped shorter caulocystidia, and a paler brown pileus ( Menolli et al. 2015b). From the Dominican Republic, P. stenotrichus differs in producing a paler brown non-sulcate pileus, smaller cheilocystidia (25–50 × 14–20 µm), pleurocystidia lacking mucilage, differently shaped non-mucronate pileipellis elements, and similarly shaped but shorter caulocystidia (31–63 × 12–24 µm) ( Justo et al. 2012). Pluteus castaneorugosus from Vietnam differs in having smaller spores (5–6 × 4.5–5.5 µm), smaller non-mucilagenous pleurocystidia (35–55 × 15–22 µm), smaller thick-walled cheilocystidia (25–43 × 14–20 µm), and a differently shaped non-mucronate pileipellis ( Malysheva et al. 2020). Finally, P. iguazuensis from Argentina ( Singer 1958) and Brazil ( Menolli & Capelari 2016) differs in having a non-rugose, non-rimose pileus, shorter cheilocystidia, non-mucilaginous pleurocystidia, lack of caulocystidia, and lack of lageniform or mucronate elements in the pileipellis.

Figures

FIGURE 37a–e. Maximum Likelihood phylogeny of sect. Celluloderma based on ITS sequence data (-lnL = 18618.671374). Sequences of specimens from Vanuatu are indicated in bold type. Stars indicate type specimens. Values separated by / refer to ML bootstrap proportions and Bayesian posterior probabilities. Only values greater than 70/0.70 are shown. Nodes receiving support values greater than 90/0.95 are highlighted in bold.

FIGURE 48. Basidiome of Pluteus tatafuensis (JAD 304 holotype). Scale bar = 10 mm. Photos by: Brian Perry.

FIGURE 49. Pluteus tatafuensis. a. Basidiospores. b. Basidia. c. Basidioles. d. Pileipellis terminal elements. e. Cheilocystidia. f. Caulocystidia. g. Pleurocystidia. Scale bar = 10 µm. Drawings by: Jonathan del Rosario.