Pluteus ornatocystidiatus, 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 : 60-62

Pluteus ornatocystidiatus J.A. del Rosario & B.A. Perry, sp. nov. ( Figs. 29 , 30 )

MycoBank no:—854225

Holotype:— VANUATU. Tafea Province: Tanna, Yanemari / Lighthouse and Mount Kuning area , 19°37.602′S, 169°25.870′E, elev. 286 m, 30 August 2018, coll. J. A. del Rosario, JAD 167 ( HAY).

Etymology:— ornato ( L.) = ornate, cystidiatus ( L.) = cystidia; in reference to the abundant apically ornamented cystidia on all tissues.

Diagnosis:— Pluteus ornatocystidiatus from Tanna is characterized by a dark fading to pale tan areolate-squamulose disc, tan glabrous pileus with a pellucid-striate margin and a white stipe with tan floccules and a broadened base. Microcharacters include subglobose spores (6.1 × 4.9 µm), clavate sometimes mucronate cheilocystidia, lageniform mucronate or clavate pleurocystidia, a trichohymeniderm pileipellis comprised of lageniform, broadly clavate mucronate terminal elements that occasionally have thickened walls and brown pigmentation, fusoid mucronate caulocystidia, and an absence of clamp connections.

Description:— Pileus 25–55 mm diam., convex to plano-convex, margin slightly sulcate or not; surface dull to pellucid-striate up to half-way from margin, hygrophanous, disc areolate-squamulose in expansion, glabrous with pulverulent patches towards the margin; disc and squamules dark tan (oac646–oac647) fading to tan (oac668–oac669) turning cream (oac696–oac697) at the margin. Context up to 3 mm thick, pale pinkish brown. Lamellae free, close to crowded with 3 tiers of lamellulae. Stipe 30–55 × 4–6 mm, central, terete, cylindrical over a broadened base, hollow; surface pearlescent, dry, minutely flocculose or appressed-fibrillose, white overall with some tan floccules becoming most dense at the base. Odor indistinct. Taste indistinct.

Basidiospores 5–7 × 4–6 µm [x m = 6.08 ± 0.48 × 4.84 ± 0.5 µm, Q = 1–1.75, Q m = 1.26 ± 0.15 µm, n = 50, s = 1], subglobose to ellipsoid, smooth, hyaline, with a guttule, inamyloid, thick-walled. Basidia 16–24 × 4–7 µm, clavate, 4-spored or 2-spored, guttulate, hyaline, thin-walled, sterigmata 2–3 × 0.5–1 µm. Basidioles 15–28 × 5–10 µm, clavate, guttulate, hyaline, thin-walled. Lamellar edge sterile. Cheilocystidia 30–65 × 8–22 µm, clavate to narrowly lageniform or fusoid, obtuse or occasionally mucronate to subcapitate, hyaline, thin-walled. Pleurocystidia 30–68 × 8–32 µm, lageniform to fusoid-ventricose or narrowly utriform, mucronate with regular to irregular or strangulate apical projections, hyaline, thin-walled; some 50–78 × 25–36 µm, ovoid to broadly clavate, obtuse without apical projections, hyaline, thin-walled. Pileipellis a trichohymeniderm with pileocystidia, composed of a majority of cells 50–140 × 13–42 µm, clavate to broadly clavate, fusiform to fusoid-ventricose or lageniform, obtuse or frequently capitate or mucronate, typically with brown plasmatic pigment or occasionally hyaline, non-incrusted, non-gelatinous, thin-walled; pileocystidia 110–210 × 12–45, common, fusiform to fusoid, frequently mucronate with an elongated appendage (up to 85 µm long) or obtuse, with brown plasmatic pigment or occasionally hyaline, thin to evenly or apically thick-walled (up to 3 µm thick). Pileus trama interwoven, composed of hyaline, non-gelatinous, thin-walled, cylindrical hyphae, 5–28 µm diam.. Lamellar trama inverse, composed of hyaline, non-gelatinous, thin-walled hyphae, 3–20 µm diam.. Stipitipellis a cutis, composed of hyaline, non-incrusted, non-gelatinous, thin-walled hyphae, 4–12 µm diam.. Caulocystidia 30–120 × 13–22, clustered or scattered, clavate to broadly clavate or fusoid, capitate or mucronate, hyaline, thin-walled. Clamp connections absent in all tissues examined.

Habitat and known distribution:—Gregarious on decaying wood in subtropical lowland-montane secondary broadleaf- Podocarpaceae rainforest containing Balanops pedicellata ( Balanopaceae ), Calophyllum neoebudicum ( Calophyllaceae ), Cryptocarya wilsonii ( Lauraceae ), Ficus wassa ( Moraceae ), Ixora aneityensis ( Rubiaceae ), Podocarpus vanuatuensis ( Podocarpaceae ), and Syzygium spp . ( Myrtaceae ), Vanuatu (Tanna).

Material examined:— VANUATU. Tafea Province: Tanna, Yanemari / Lighthouse and Mount Kuning area , 19°37.602′S, 169°25.870′E, elev. 286 m, 30 August 2018, coll. J. A . del Rosario , JAD 167 ( HAY) .

Notes:—In comparison to P. ornatocystidiatus , the species P. heteromarginatus Justo (2011: 472) from the U.S.A. is close macromorphologically, but differs primarily by lacking a flocculose stipe. Micromorphologically it differs by having slightly smaller pleurocystidia, smaller cheilocystidia lacking apical appendages, narrower pileipellis terminal elements without thick walls or elongated apical appendages, and narrower caulocystidia ( Justo et al. 2011b). Pluteus aeolus (Berkeley & Broome) Saccardo (1887: 666) , a tropical species from Sri Lanka, also has macromorphological similarities, but differs due to a lack of clavate or thick-walled pileipellis terminal elements, lack of mucronate cheilocystidia, and no pleurocystidia ( Pegler 1986). Pluteus longistriatus Peck (Peck) (1835: 137) reported from North and South America is also superficially similar, but fundamentally differs in the absence of apical appendages on the pleurocystidia, cheilocystidia and caulocystidia, lacking apical appendages or thickened walls in the pileipellis terminal elements, and having less lageniform and non-mucronate caulocystidia ( Menolli & Capelari 2010, Singer 1956, 1958). Based on ITS phylogenetic analysis ( Fig. 15a ) P. ornatocystidiatus is placed on an unsupported branch ( BS 39 %, PP 0.76) sister to the Italian species P. pulcherrimus Ferisin & Dovana (2019: 24) . Pluteus pulcherrimus is macromorphologically much closer to the Vanuatu specimen, but this species differs by slightly smaller pleurocystidia, slightly smaller cheilocystidia lacking apical appendages, and generally larger caulocystidia that are apically acute ( Ferisin & Dovana 2019). Importantly, P. pulcherrimus is distinguished by the presence of brown veins on the pileus disc, which are absent in the Vanuatu material.

Figures

FIGURE 15a–c. Maximum Likelihood phylogeny of sect. Hispidoderma based on ITS sequence data (-lnL = 7783.640376). 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, respectively. Only values greater than 70/0.70 are shown. Nodes receiving support values greater than 90/0.95 are highlighted in bold.

FIGURE 29. Basidiomes of Pluteus ornatocystidiatus (JAD 167 holotype). Scale bar = 10 mm. Photos by: Jonathan del Rosario.

FIGURE 30. Pluteus ornatocystidiatus 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.