Pluteus lalepiorum, 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 : 85-88

Pluteus lalepiorum J.A. del Rosario & B.A. Perry, sp. nov. ( Figs. 42 , 43 )

MycoBank no:—854227

Holotype:— VANUATU. Tafea Province: Aneityum, trail through Antowojon area , 20°13.142′S, 169°47.788′E, elev. 119 m, 28 July 2017, coll. J. A. del Rosario & B. A. Perry, JAD 12 ( HAY).

Etymology:—Named in honor of the Lalep family and for their contributions of the language and natural knowledge of Aneityum to the Plants mo Pipol blong Vanuatu project. In memory of Titya Kelly Lalep, who was one of the earliest contributors.

Diagnosis:— Pluteus lalepiorum from Aneityum is characterized by a hygrophanous, cream colored pileus with sooty brown floccules at the disc and a white stipe typically with similar floccules towards the base. Microcharacters include subglobose basidiospores (6.1 × 5.5 µm), fusoid-ventricose thick-walled cheilocystidia and pleurocystidia with mucilage coating some pleurocystidia, a cutis pileipellis with fragmented erect filiform brown pigmented terminal elements, similarly shaped and pigmented caulocystidia, and an absence of clamp connections.

Description:— Pileus 40–45 mm diam., hemispherical to plano-convex with an umbo, some slightly centrally depressed, margin entire or undulate; surface dull turning pellucid-striate at margin, hygrophanous, appressed-fibrillose turning glabrous at margin, disc finely flocculose; floccules and fibrils sooty brown (oac778–oac780) dense at disc, diminishing towards margin, fibrils turning cream to off-white with minute sooty brown streaks, surface pale off-white. Context 5 mm thick, white to off-white. Lamellae free, crowded with 3 tiers of lamellulae, thin, pallid tan to pale pink (oac709–oac711). Stipe 25–40 × 2.5–4 mm, central, terete, cylindrical over a bulbous base, solid; surface dull, dry, fibrous, some finely flocculose towards the base, white overall with sooty brown floccules, context white, arising from a white tomentum or not. Odor indistinct. Taste indistinct.

Basidiospores 5–7 × 5–7 µm [x m = 6.1 ± 0.54 × 5.42 ± 0.57 µm, Q = 1.0–1.4, Q m = 1.13 ± 0.13, n = 50, s = 1], globose to subglobose, smooth, hyaline, with a guttule, inamyloid, thick-walled. Basidia 16–25 × 6–8 µm, clavate, 4-spored, hyaline, guttulate, thin-walled, sterigmata 2–4 × 0.5–1 µm. Basidioles 11–19 × 6–8 µm, clavate, hyaline, guttulate, thin-walled. Lamellar edge sterile. Cheilocystidia 30–78 × 8–16 µm, clavate to fusoid-ventricose, obtuse or mucronate, hyaline, thin to thick-walled (up to 2 µm thick). Pleurocystidia 40–80 × 11–30 µm, fusoid-ventricose to narrowly lageniform or narrowly utriform, obtuse or sometimes capitate-truncate, some with apical lateral mucilage sometimes with adhering spores that obscure view, hyaline, thin to thick-walled. Pileipellis a cutis of repent hyphae with fragmented erect terminal elements (pileocystidia), composed of hyaline or brown plasmatic pigment, non-incrusted, non-gelatinous, thin-walled, cylindrical hyphae, 3–11 µm diam.; pileocystidia 30–110 × 5–10 µm, repent to erect, solitary to clustered in fascicles especially at the disc, filiform to fusoid, acute, obtuse or subcapitate, sometimes with one to multiple basal cells, typically with brown plasmatic pigment or occasionally hyaline. Pileus trama interwoven, composed of hyaline, non-gelatinous, thin-walled, clavate to inflated hyphae, 3–25 µm diam.. Lamellar trama inverse, composed of hyaline, non-gelatinous, thin-walled hyphae, 3–16 µm diam.. Stipitipellis a cutis, composed of hyaline, non-incrusted, non-gelatinous, thin-walled hyphae, 4–18 µm diam.. Caulocystidia 50–110 × 6–16 µm, similar to pileipellis terminal elements, clustered to solitary, filiform to narrowly lageniform, acute, obtuse or sometimes capitate, some with one to multiple basal cells, with brown plasmatic pigment or sometimes hyaline, thin-walled. Clamp connections absent in all tissues examined.

Habitat and known distribution:—Gregarious 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).

Material examined:— VANUATU. Tafea Province: Aneityum, trail through Antowojon area , 20°13.142′S, 169°47.788′E, elev. 119 m, 28 July 2017, coll. J. A . del Rosario & B. A . Perry , JAD 12 ( HAY) .

Notes:—The distinctly thick-walled cystidia are unusual for members of sect. Celluloderma suggesting immediate comparison to only one other known species with this trait in the section: P. crassocystidiatus Menolli & de Meijer (2014: 114) . This Brazilian species is known only from the protologue ( Menolli et al. 2015a) and compared to P. lalepiorum shares similarly shaped thick-walled pleurocystidia and cheilocystidia that contain apical mucilage, but has much longer cheilocystidia (44–110 × 11.2–24 µm). The pileipellis in P. crassocystidiatus is also different, being a euhymeniderm of smaller clavate-vesiculose cells (23–41 × 17.5–24 µm). Pluteus crassocystidiatus is also not known to have caulocystidia and has a different colored olive brown to yellowish brown pileus.

Pluteus maculosipes Singer (1961: 122) from Venezuela ( Singer 1961) and Brazil ( Menolli et al. 2015c) is micromorphologically similar in pileipellis structure and caulocystidia, but differs by lacking pleurocystidia, having thin-walled cheilocystidia without mucilage, and producing a darker pigmented basidiome. The Sri Lankan P. glyphidiatus has similar pileipellis elements and mucilaginous lamellar cystidia, but differs by its yellow colored basidiome, and less lageniform, non-thick-walled cheilocystidia and pleurocystidia ( Pegler 1986, Singer 1956). A recently described species from Thailand, P. saisamorniae Wannathes, J. Kumla & N. Suwannarach (2022: 9) , similarly shares thick-walled pleurocystidia and cheilocystidia, and has similarly shaped pileipellis terminal cells, however P. saisamorniae is phylogenetically distinct by belonging in sect. Hispidoderma , lacks mucilage on the cystidia, and has a brown basidiome.

ITS phylogenetic analysis ( Fig. 37d ) places P. lalepiorum on a moderately supported branch (BS 82 %, PP 0.99) within the ephebeus clade recognized by Justo et al. (2011b). Within this clade, the Vanuatu species is morphologically close to the Brazilian P. halonatus Menolli, Justo & Capelari (2015: 1213) , with which it shares a similar pileipellis structure and mucilaginous pleurocystidia. Pluteus lalepiorum differs from this species as the latter forms shorter nonthick-walled-pleurocystidia and cheilocystidia, and has a distinct brown fibrillose pileus ( Menolli et al. 2015b). Pluteus lalepiorum is positioned on a branch with low internal node statistical support containing P. squamulososulcatus E.F. Malysheva & O.V. Morozova (2020: 99) ( MT611234 ) and specimens identified as P. aff. ephebeus ( KM983675 , KM983676 ), P. cf. fastigiatus ( KM983678 ) and P. cf. fuliginosus ( KM983677 ). Recently described from Vietnam, P. squamulososulcatus differs in having a sulcate, gray-pink squamulose pileus, non-thick-walled and non-mucilaginous pleurocystidia and cheilocystidia, a cutis pileipellis without pileocystidia, and lacks caulocystidia ( Malysheva et al. 2020). The Brazilian specimen tentatively identified as P. cf. fastigiatus shares similarly sized mucilaginous pleurocystidia and cheilocystidia, but differs due to the cystidia not being thick-walled, the basidiome being dark pigmented, having a different pileipellis, and lacking caulocystidia ( Menolli & Capelari 2016). Pluteus cf. fuliginosus shares with P. lalepiorum a similar pileipellis structure and mucilaginous pleurocystidia and cheilocystidia, and although the pleurocystidia are also apically thick-walled, they differ due to having apical prongs; a dark pigmented pileus, thin-walled cheilocystidia, and lacking caulocystidia ( Menolli & Capelari 2016).

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 42. Basidiomes of Pluteus lalepiorum (JAD 12 holotype). Scale bar = 10 mm. Photo by: Brian Perry.

FIGURE 43. Pluteus lalepiorum. 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.