Pluteus macrocystidiatus

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 : 54-59

Pluteus macrocystidiatus nom. prov. ( Fig. 26 )

Diagnosis:— Pluteus macrocystidiatus from Futuna is characterized by a small, cream, convex, fibrillose, marginally eroded pileus, serrated lamellae, and a similarly ornamented and colored stipe with a bulbous base arising from a white tomentum. Microcharacteristics include subglobose to broadly ellipsoid spores (8.6 × 7.7 µm), rare sphaeropedunculate cheilocystidia, scattered fusiform to lageniform pleurocystidia, clustered and distinctly large broadly clavate caulocystidia, and an absence of clamp connections.

Description:— Pileus 15 mm diam., convex, margin slightly sulcate, slightly eroded; surface hygrophanous, dry, appressed-fibrillose; fibrils off-white to cream (oac815), densest at the disc, less dense towards the margin, underlying surface pale pink to pink-brown (oac793). Context up to 2 mm thick, pale pink to pink-brown (oac793). Lamellae free, crowded with 5 tiers of lamellulae, thin, pink-brown (oac793), margin slightly serrate-eroded. Stipe 10 × 1.5 mm, central, cylindrical over a bulbous base arising from a white tomentum (upwards 2 mm from base), hollow; surface dry, dull, fibrous, flocculose at base; white fibrils over a tan (oac795) surface, context white. Odor indistinct. Taste not observed.

Basidiospores (7–) 8–10 × (6–) 7–9 µm [x m = 8.62 ± 0.75 × 7.63 ± 0.8 µm, Q = 1–1.5, Q m = 1.1 ± 0.1, n = 50, s = 1], subglobose to occasionally broadly ellipsoid, smooth, hyaline, with a guttule, inamyloid, thick-walled. Basidia not observed. Basidioles 16–22 × 8–10 µm, clavate, hyaline, thin-walled. Cheilocystidia 26–52 × 14–25 µm, rare, seldom forming a well-developed strip on the lamellar edge, sphaeropedunculate to broadly clavate, obtuse, hyaline, thin-walled. Pleurocystidia 42–76 × 8–22 µm, scattered, fusiform to lageniform, obtuse to truncate or capitate, hyaline, thin-walled. Pileipellis ambiguous (due to weathered nature of specimen), possibly a cutis, composed of cylindrical, hyaline, non-incrusted, non-gelatinous, thin-walled hyphae, 3–12 µm diam.; terminal elements 32–115 × 5–11 µm, repent or occasionally suberect, clavate to cylindro-clavate, obtuse. Pileus trama interwoven, composed of hyaline, non-gelatinous, thin-walled, cylindrical hyphae, 3–24 μm diam.. Lamellar trama inverse, composed of hyaline, non-gelatinous, thin-walled hyphae, 3–9 µm diam.. Stipitipellis a cutis, composed of hyaline, non-incrusted, non-gelatinous, thin-walled hyphae, 3–9 µm diam.. Caulocystidia 25–106 × 8–27 µm, common, solitary to clustered, clavate to broadly clavate, obtuse, hyaline, thin-walled. Clamp connections absent in all tissues examined.

Habitat and known distribution:—Solitary on decaying wood in subtropical montane primary broadleaf rainforest containing Ascarina diffusa ( Chloranthaceae ), Claoxylon fallax ( Euphorbiaceae ), Diospyros ferra ( Euphorbiaceae ), Dillenia biflora ( Dilleniaceae ), Ficus storckii ( Moraceae ), Geissois denhamii ( Cunoniaceae ), Metrosideros vitiensis ( Myrtaceae ), Phyllanthus myrianthus ( Phyllanthaceae ), Plerandra actinostigma ( Araliaceae ), Schefflera neoebudica ( Araliaceae ), and Syzygium chanelii ( Myrtaceae ), Vanuatu ( Futuna).

Material examined:— VANUATU. Tafea Province: Futuna, low slopes of Mount Tatafu from Natangi , 19°31.309′S, 170°13.536′E, elev. 281 m, 16 August 2019, coll. J. A . del Rosario & B. A . Perry , JAD 302 ( HAY) .

Notes:—Unfortunately, sparse material and the poor condition of the Vanuatu specimen prevented a clear characterization of the pileipellis, which may be a cutis. Because of this missing character and closeness to a number of similar species, a provisional identification is proposed for this study. The small stature of the Vanuatu specimen suggests comparison to a number of Pluteus species. Pluteus delicatulus C.K. Pradeep & Vrinda (2006: 95) is a similarly small, fragile species from India, however it differs due to the darker basdiomes, smaller spores, smaller non-lageniform pleurocystidia, absence of caulocystidia, and an epithelioid pileipellis ( Pradeep et al. 2006). Pluteus aquosus has similar micromorphology, but differs by lacking a serrate lamellar edge, having a pure white stipe lacking a bulbous base stipe, lacking white basal tomentum, having smaller spores, and ventricose cheilocystidia ( Singer 1956, 1958, 1961). Pluteus albidus shares many morphological similarities, but differs slightly by its smaller subglobose spores, versiform cheilocystidia, smaller caulocystidia, and lacks serrate gill edges ( Desjardin & Perry 2018). Pluteus espeletiae Singer (1961: 120) from Venezuela ( Singer 1961) similarly shares a crenate gill edge, large spores (8–8.8 × 6.8–7.5 µm), and pleurocystidia shape, but differs due to having a scaly disc, ventricose cheilocystidia, pigmented cystidia, and lacking caulocystidia.

ITS data phylogenetic analysis ( Fig. 15b ) places P. macrocystidiatus with an undetermined Pluteus species from Taiwan ( MK041296 ) within the general plautus / longistriatus clade recognized by Justo et al. (2011b). A pairwise comparison of the two aligned, overlapping ITS sequences reveals a 99.84 % similarity suggesting these may be conspecific. Currently, the Taiwanese material has not been studied and unfortunately morphological data is currently unavailable for comparison. Regardless, assuming these two are the same taxon there is a wide gap in a distribution between Taiwan and Vanuatu’s island of Futuna. Similarity between Taiwan’s range of northern subtropical climates to southern tropical and Vanuatu’s subtropical climate may explain the species’ preferred conditions. This species possibly occurs elsewhere throughout the Pacific, but incomplete regional records of this group combined with its general small stature suggest it is easily overlooked. The particular combination of the serrate lamellar edge, sparse cheilocystidia, and rather large spores and caulocystidia (hence the epithet macrocystidiatus ) may be distinct enough to describe the species as new. It would be ideal to compare the Taiwanese specimen to the Futuna material and determine if these specific characters are shared consistently in both. Due to incomplete data and for the sake of the study, the Vanuatu specimen is tentatively identified with a nom. prov. pending further investigation of additional material.

Pluteus neochrysaegis Menolli & de Meijer in Menolli Jr., de Meijer & Capelari, Nova Hedwigia 100(1–2): 135 (2014) [2015] ( Figs. 27 , 28 )

Diagnosis:— Pluteus neochrysaegis from Aneityum is distinguished by a grayish tan fading to white plano-convex pileus with a pellucid-striate margin and a rugose-venose uplifted white context disc. The bulbous based stipe is variably pallid tan fibrillose-flocculose. Microscopic characters include subglobose spores (6.3 × 5.6 µm), fusoid, thin to thick-walled acute cheilocystidia and obtuse pleurocystidia, an epithelioid hymeniderm pileipellis of pyriform cells with fusoid terminal cells over a cutis subpellis, fusoid-ventricose caulocystidia, pale grayish brown pigments throughout the cutis subpellis, stipitipellis, and caulocystidia, and an absence of clamp connections.

Description:— Pileus 27–42 mm diam., broadly plano-convex with a broad slight central depression, slightly to broadly umbonate, margin minutely plicate in some; surface dull, dry, glabrous to appressed-fibrillose with minute exposed rivulose-pulverulent patches, disc absent or radially rugose-venose up to three-fourths the pileus width towards margin, veins splitting to expose and uplift the white context, margin pellucid-striate; surface overall pallid tan (oac690, oac710–oac711, oac730–oac732) with slight dull yellowish gray (oac723–oac725) tinges fading to white or grayish tan (oac674–oac676) towards the margin. Context 1.5–3 mm thick, white. Lamellae free, crowded, with 3–4 tiers of lamellulae, thin, dull pink (oac610–oac612). Stipe 20–50 × 3–5 mm, central, terete, cylindrical over a subbulbous to bulbous base, solid to hollow; surface dull, dry, longitudinally fibrillose-striate and/or minutely flocculose, pale tan (oac653–oac655) over a white surface, context white. Odor indistinct. Taste indistinct.

Basidiospores 5–7 (–8) × 5–7 µm [x mr = 6.22–6.5 × 5.52–5.62 µm, x mm = 6.3 ± 0.14 × 5.57 ± 0.1 µm, Q = 1.0–1.5, Q mr = 1.11–1.18, Q mm = 1.1 ± 0.14, n = 50, s = 4], subglobose to broadly ellipsoid, smooth, hyaline, with a guttule, inamyloid, thick-walled. Basidia 20–35 × 6–8 µm, clavate, 4-spored, hyaline, guttulate, thin-walled, sterigmata 2–4 × 0.5–1 µm. Basidioles 12–26 × 5–8 µm, clavate, hyaline, guttulate, thin-walled. Lamellar edge sterile. Cheilocystidia 35–83 × 6–25 µm, lageniform to broadly lageniform or fusoid-ventricose, obtuse, acute, or occasionally capitate, hyaline, thin to evenly or apically thick-walled (up to 3 µm thick) especially in larger cystidia. Pleurocystidia 35–90 × 15–25 (–35) µm, scattered to common, fusiform to narrowly lageniform, obtuse or rarely mucronate, hyaline, thin to thick-walled (up to 3 µm thick) especially in larger cystidia; rarely 34–46 × 10–18 mm, fusoid-ventricose, acute or corniculate with 2–4 poorly developed hooks, hyaline, thin to thick-walled. Pileipellis an epithelioid hymeniderm with pileocystidia over a subpellis, majority of terminal elements 12–30 × 5–12 µm, sphaeropedunculate to clavate, obtuse or rarely mucronate, hyaline, non-incrusted, non-gelatinous, thin-walled; pileocystidia 28–55 (–71) × 8–16 µm, scattered to abundant especially at the disc, fusiform to narrowly lageniform, obtuse, acute, infrequently capitate or rarely mucronate (up to 50 µm long), hyaline, thin to evenly or apically thick-walled especially in lageniform elements; subpellis a cutis of repent hyphae, composed of pale brown plasmatic pigmented, non-incrusted, non-gelatinous, thin-walled hyphae, 3–10 µm diam.. Pileus trama interwoven, composed of hyaline, non-gelatinous, thin-walled, cylindrical to inflated hyphae, 4–23 µm diam.. Lamellar trama inverse, composed of hyaline, non-gelatinous, thin-walled hyphae, 3–18 µm diam.. Stipitipellis a cutis, composed of hyaline or with patches of plasmatic pale brown pigment, non-incrusted, non-gelatinous, thin-walled hyphae, 3–14 µm diam.. Caulocystidia 20–62 × 6–16 µm, solitary or often clustered, lageniform to fusoid-ventricose, acute or rarely subcapitate, hyaline or with pale brown plasmatic pigment, thin to thick-walled especially in larger cystidia. Clamp connections absent in all tissues examined.

Habitat and known distribution:—Solitary to gregarious on decayed wood in subtropical montane primary broadleaf rainforest to cloud forest containing Balanops pedicellata ( Balanopaceae ), Diospyros sp. ( Ebenaceae ), Ficus smithii ( Moraceae ), Garcinia platyphylla ( Clusiaceae ), Ilex vitiensis ( Aquifoliaceae ), Melicope latifolia ( Rutaceae ), Metrosideros collina ( Myrtaceae ), Plerandra actinostigma ( Araliaceae ), Scaevola cylindrica ( Goodeniaceae ), Semecarpus tannaensis ( Anacardiaceae ), and Syzygium spp . ( Myrtaceae ) and 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 Brazil (Paraná).

Material examined:— VANUATU. Tafea Province: Aneityum, Anloulanelcau area , trail to Transect 11, 20°13.066′S, 169°47.406′E, elev. 188 m, 29 July 2017 coll. J. A . del Rosario, JAD 17 ( HAY); Aneityum, Mount Inhetiji, lowland forest in former taro terraces close to Anecro , 20°12.567′S, 169°51.102′E, elev. 145 m, 12 December 2018, coll. J. A . del Rosario , JAD 244 ( HAY); same location, 12 December 2018, coll. P . Dovo, JAD 245 ( HAY); Aneityum, Anecro, footpath to river near Chief Nicolas’s house, 20°12.490′S, 169°51.983′E, elev. 76 m, 14 December 2018, coll. J. A . del Rosario , JAD 265 ( HAY) .

Notes :— Pluteus neochrysaegis is currently known and originally described from Paraná state of Brazil ( Menolli et al. 2015a). The material collected from Aneityum Island fits well with the original description with minor caveats. Coloration in the pileus is slightly paler, albeit across collections variation occurs likely due to environmental conditions. In collection JAD 265 , the distinct uplifted white context veins radiate from the disc, however multiple specimens in this collection show that the magnitude of this rugose-venose ornamentation varies as this is significantly reduced in the smallest basidiome and does not occur in the other collections .

Menolli et al. (2015a) distinguished P. conizatus (Berkeley & Broome) Saccardo from P. neochrysaegis by its pale yellow stipe, however this trait may not necessarily be consistent as the Vanuatu material has a similarly colored pale yellow stipe that varies but occurs across all specimens. Menolli et al. also discussed pileipellis similarity between P. neochrysaegis and P. chrysaegis , and distinguished P. neochrysaegis as different in having shorter pleurocystidia, dimorphic cheilocystidia, both lamellar cystidia types being pigmented, and ellipsoid spores. The Vanuatu material recognized as P. neochrysaegis shares similarly sized and shaped hyaline pleurocystidia compared to the Tafean collections and other regional accounts of P. chrysaegis . Between the Brazilian and Vanuatu material of P. neochrysaegis , the Brazilian specimen has smaller pleurocystidia (30–44 × 6.2–11.2 µm). The Vanuatu specimens lack pigmented cheilocystidia, which is present in the Brazilian material, but shares similarly sized and dimorphic thick-walled cheilocystidia. All the Vanuatu specimens of P. chrysaegis share this dimorphic variety of cheilocystidia with intermediate elements as well, so it is uncertain if this trait proposed by Menolli et al. as distinctive should be considered an exclusive feature of P. neochrysaegis . For the most part, the micromorphology between these species is nearly homogenous. One exception, that was also recognized by Menolli et al., could be the ellipsoid spores in P. neochrysaegis , while P. chrysaegis has typically subglobose spores. The primary means of distinguishing among these species would be through their pileus coloration as P. neochrysaegis has a dull grayish brown pileus fading to white without or with white veins, and P. chrysaegis typically has a brilliant to dull yellow pileus with brown veins.

Pluteus amphicystis Singer (1958:213) from Bolivia is a superficially similar species ( Singer 1958).Pegler reported a collection from Martinique and provided a line drawing that strongly resembles the stature of P. neochrysaegis (Fig. 58, Pegler 1983a). Both Singer and Pegler reported the rugose-venose elements of the pileus and described this as ‘scrobiculate’. Singer described the pileus as “yellow, center watery melleous…finely tomentose or subfibrillose…” ( Singer 1958), while Pegler described the color as light ochraceous-buff with yellow ocher granules and the marginal edge being transparent ( Pegler 1983a).Both authors described the presence of metuloid pleurocystidia and cheilocystidia like those of P. neochrysaegis . The important distinction between these taxa is in regard to Singer’s emphasis of the metuloids being similar to those of Inocybe spp . that includes the presence of apical crystals, which Pegler also observed in the Martinique material. The presence of these apical crystals on the pleurocystidia were confirmed and imaged via electron microscopy during a re-examination of the type and with supplementary material from Mexico ( Fig. 2 , Rodríguez & Guzmán-Dávalos 2007). Pluteus amphicystis can also be distinguished based on its pileipellis, which Singer described as consisting of elongated hyphae with terminal elements having broadly rounded tips and additional forms similar to the metuloid cystidia ( Singer 1958). Pegler (1983a) describes this as a repent epicutis with dermatocystidia (60–160 × 5–24 µm) forming erect fascicles at the disc, and Rodríguez and Guzmán-Dávalos (2007) illustrated a filamentous pileipellis, noting some of the elements with thick walls and becoming suberect near the pileus center. As mentioned, pileipellis interpretation has caused difficulty in the taxonomy of Pluteus spp . . Overall, the hymeniderm pileipellis and lack of cystidia with apical crystals separates the Vanuatu material from P. amphicystis and better identifies it as P. neochrysaegis .

Figures

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

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 26. Pluteus macrocystidiatus. a. Basidiospores.b. Basidioles.c. Pileipellis terminal elements.d. Cheilocystidia.e. Caulocystidia. f. Pleurocystidia. Scale bar = 10 µm. Drawings by: Jonathan del Rosario.

FIGURE 27. Basidiomes of Pluteus neochrysaegis. a. Non venose-rugose forms of Pluteus neochrysaegis (JAD 244). b. Venose-rugose form of Pluteus neochrysaegis (JAD 265). Scale bar = 10 mm. Photos by: Jonathan del Rosario.

FIGURE 28. Pluteus neochrysaegis. 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.