Pluteus velutinus Pradeep, Justo & Vrinda, Mycological Progress, 2012

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 : 71-78

Pluteus velutinus Pradeep, Justo & Vrinda, Mycological Progress 11: 871 (2012) ( Fig. 36 )

Diagnosis:— Pluteus velutinus from Aneityum is characterized by a brown pruinose pileus with pulverulent patches exposing a white context, and a tan fibrillose stipe with a subbulbous base. Microcharacters include subglobose spores (6.5 × 5.5 µm), clavate cheilocystidia, clavate or fusoid-ventricose pleurocystidia, a trichohymeniderm pileipellis comprised of fusoid terminal cells containing brown pigment, similarly pigmented clavate caulocystidia, and an absence of clamp connections.

Description:— Pileus 35 mm diam., hemispherical; surface pruinose or somewhat pearlescent, dry, finely areolatereticulate with pulverulent patches exposing the underlying context; surface uniformly brown-toned (oac722–oac723). Context 1.5 mm thick, white. Lamellae free, somewhat subdistant with 2–3 tiers of lamellulae, regular, dark pinkish brown (oac659–oac660). Stipe 55 × 5 mm, central, terete, cylindrical over a subbulbous base, solid; surface pearlescent, dry, longitudinally fibrillose, overall tan (oac653–oac655). Taste indistinct. Odor indistinct.

Basidiospores (4–) 5–7 (–8) × (4–) 5–7 µm [x m = 6.2 ± 0.82 × 5.8 ± 0.66 µm, Q = 1–1.33, Q m = 1.07 ± 0.09, n = 50, s = 1], globose to subglobose, smooth, hyaline, with a guttule, inamyloid, thick-walled. Basidia 15–20 (–27) × 5–8 µm, clavate, 4-spored, hyaline, with a guttule, thin-walled, sterigmata 1.5–4 × 0.5–1 µm. Basidioles 10–20 × 5–8 µm, clavate, hyaline, with a guttule, thin-walled. Lamellar edge sterile. Cheilocystidia 32–80 × 8–25 µm, clavate to broadly clavate, fusoid to narrowly utriform or sphaeropedunculate, obtuse, hyaline, thin-walled. Pleurocystidia 38–96 × 10–55 µm, clavate to ovoid or fusoid-ventricose to narrowly utriform, obtuse, seldom truncate or rarely with a mucronate appendage (up to 8 µm long), one observed with a median constriction, hyaline, thin to rarely thick-walled especially in larger ovoid elements. Pileipellis a trichohymeniderm, composed of a majority of cells 80–200 × 8–16 µm, clavate to cylindro-clavate mixed with 28–75 × 8–14 µm lageniform to fusoid or occasionally globose, obtuse or seldom capitate, with brown plasmatic pigment or hyaline, non-incrusted, non-gelatinous, thin-walled. Pileus trama interwoven, composed of hyaline or occasionally with brown plasmatic pigment, non-gelatinous, thin-walled, cylindrical to inflated hyphae, 3–17 (–28) µm diam.. Lamellar trama inverse, composed of hyaline, non-gelatinous, thin-walled hyphae, 3–24 µm diam.. Stipitipellis a cutis, composed of hyaline, non-incrusted, non-gelatinous, thin-walled hyphae, 3–24 µm diam.. Caulocystidia 25–48 (–80) × 8–20 µm, abundant, solitary to clustered, clavate to cylindro-clavate or seldom fusoid-ventricose, obtuse, with brown plasmatic pigment or hyaline, thin-walled. Clamp connections absent in all tissues examined.

Habitat and known distribution:—Solitary on decayed wood in subtropical montane primary broadleaf- Araucariaceae / Podocarpaceae rainforest containing Agathis macrophylla ( Araucariaceae ), Balanops pedicellata ( Balanopaceae ), Calophyllum neoebudicum ( Calophyllaceae ), Dendrocnide latifolia ( Urticaceae ), Ficus septica ( Moraceae ), Ficus smithii ( Moraceae ), Garcinia platyphylla ( Clusiaceae ), Geissois denhamii ( Cunoniaceae ), Hernandia moerenhoutiana ( Hernandiaceae ), Macaranga dioica ( Euphorbiaceae ), Podocarpus vanuatuensis ( Podocarpaceae ), Polyscias cissondendron ( Araliaceae ), and Syzygium spp . ( Myrtaceae ), Vanuatu (Aneityum). Also known from Asia ( Japan, India, Mongolia, Russia, South Siberia, Vietnam), Europe ( Italy), U.S.A. (Hawaii).

Material examined:— VANUATU. Tafea Province: Aneityum , area around and within transect 11, 20°12.622′S, 169°47.578′E, elev. 294 m, 8 August 2017, coll. J. A del Rosario & B. A . Perry , JAD 53 ( HAY) .

Notes:—The original description of P. velutinus Pradeep, Justo & Vrinda (2012: 871) is based on an Indian holotype and collections originating from Japan ( Pradeep et al. 2012). Additional reports have extended the species’ distribution to Brazil ( Menolli et al. 2015c), Vietnam ( Malysheva et al. 2020, 2023), across Russia ( Malysheva et al. 2016), and to Italy and Slovenia ( Ferisin & Dovana 2016, 2019). According to ITS data ( MW018888 , MW018907 ) in this study’s phylogenetic analysis ( Fig. 15b ), the species may also occur in Hawaii, U.S. A..

The specimen from Aneityum matches well in comparison to previous descriptions of P. velutinus , but with some minor differences. The Vanuatu material diverges based on rarity of pleurocystidia with digitate apical projections (observed once) versus other descriptions that report this trait to be common. The absence of apical digitate projections on pleurocystidia appears to have been observed in recently described material from Vietnam by Malysheva et al. (2023), but they have also observed it as common in collected material from a previous study ( Malysheva et al. 2020). However, this particular pleurocystidia ornamentation does not seem readily consistent based on line drawings from the protologue, as the Indian holotype lacks pleurocystidia with apical projections while the Japanese material’s pleurocystidia are ornamented ( Fig. 3 e 2 , Pradeep et al. 2012). According to the holotype description, the species is distinguished by this character, although they are rarer on the cheilocystidia and common on the pleurocystidia. Based on other reports of P. velutinus the frequency and variation of apical ornamentation does not appear to be only restricted to pleurocystidia, but occurs on other taxonomically informative structures, suggesting a high degree of morphological diversity within the species. The pileipellis terminal elements have been described as being irregularly shaped or having apical projections, as seen in material from Russia, Japan, and Italy, but less so in Brazilian, Indian, Vietnamese, or the Vanuatu material ( Ferisin & Dovana 2016, Malysheva et al. 2016, 2020, 2023, Menolli et al. 2015 c, Pradeep et al. 2012). A lesser emphasized cystidia character has been described as “undulating” ( Menolli et al. 2015c) or “strangulated” ( Ferisin & Dovana 2016) in caulocystidia of the Brazilian and Indian material, appearing as a median constriction in the Vanuatu specimen’s caulocystidia and pleurocystidia, and occurring in the cheilocystidia and pileipellis terminal cells of the Brazilian and Russian material respectively. Pleurocystidia with pale brown plasmatic pigment have been reported from Brazilian, Russian, and Vietnamese material, but not in the others nor the Vanuatu specimen. The Vanuatu specimen does share the presence of brown plasmatic pigment in caulocystidia and pileipellis hyphae, and this does appear consistent with all other accounts. Spore size and shape appears to vary across specimens, as the Vanuatu and Russian material appear to have more globose/subglobose spores while the others are more ellipsoid.

Phylogenetic analysis of ITS data ( Fig. 15b ) places the Vanuatu specimen in a weakly supported clade (BS 69 %, PP 0.93) with Vietnamese specimens of P. cf. velutinus ( MT611241 , MT611242 ) that subtends the other P. velutinus sequences within the stronger supported clade encompassing them. Pairwise analysis of overlapping regions of the ITS data show the Vietnamese specimen is 99.29 % similar to the Vanuatu sequence, whereas the Indian holotype is 97.26 % similar and the remaining sequences are 97.35 % similar. Malysheva et al. (2020, 2023) did not firmly identify their material due to it being phylogenetically different from the other P. velutinus specimens, and not having additional material from the Indochinese Peninsula region for comparison to propose a separate species. Malysheva et al. considered their material close to the Russian specimens based on spore size, but differing based on paler pileus color and cheilocystidia pigmentation. As the Vanuatu specimen is phylogentically closer to the Vietnamese specimen, it is worth noting that although spore size is similar to both the Russian and Vietnamese material (not typically exceeding a length of 7.5 µm according to Malysheva et al.) the pigmentation is absent in the cheilocystidia, and this character may not be enough to warrant a separate species.

Early reports of P. velutinus considered it to be a pantropical species ( Menolli et al. 2015c) with the Japanese material being an exception, until additional records from temperate Italy and Russia surfaced ( Ferisin & Dovana 2016, Malysheva et al. 2016). The species is better known now to be cosmopolitan as it has been found to occur in tropical, temperate, and subtropical climates across multiple continents and both hemispheres. Pradeep et al. (2012) and Menolli et al. (2015c) note the difficulty in explaining this distribution pattern or distinguishing a center of origin for the species. This raises the question of how highly variable climates may have influenced the establishment of the species. Menolli et al. (2015c) compared climatic data of the areas during the time of fructification for each collection among Japan, Brazil, and India and found similar relative humidity and slightly similar average temperatures between the Japanese and Indian collections, while the Brazilian material was collected during a tropical rainy season with much warmer temperatures. Similarly, the Vanuatu specimen was collected during the dry season of a subtropical climate country. The case for a new record from isolated islands such as Vanuatu may further complicate things or provide a stronger case for anthropic dispersal.

Figures

FIGURE 2. Basidiome of Pluteus albostipitatus (BAP 930). Scale bar = 10 mm. Photo by: Brian Perry.

FIGURE 3. Pluteus albostipitatus. a. Basidiospores. b. Basidia. c. Basidioles. d. Pileipellis terminal elements. e. Cheilocystidia. f. Pleurocystidia. Scale bar = 10 µm. Drawings by: Jonathan del Rosario.

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 36.Pluteus velutinusa.Basidiospores.b.Basidia.c.Basidioles.d.Pileipellis terminalelements.e.Cheilocystidia.f.Caulocystidia. g. Pleurocystidia. Scale bar = 10 µm. Drawings by: Jonathan del Rosario.