Pluteus fernandezianus Singer, Lloydia, 1958

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 : 47-51

Pluteus fernandezianus Singer, Lloydia 21: 220 (1959) ( Figs. 22 , 23 )

Diagnosis:— Pluteus fernandezianus from Aneityum is characterized by a pileus with a disc composed of radiating dark brown pustules fading towards the margin over a pallid tan surface, marginate lamellae with a grayish brown edge, and a white stipe with minute grayish brown fibrils concentrating at the bulbous base. Microcharacters include broadly ellipsoid basidiospores (7.8 × 6.1 µm), clavate pale brown pigmented cheilocystidia, lageniform infrequently pale brown pigmented pleurocystidia, a trichodermal pileipellis made up of filiform pale brown pigmented terminal elements, narrowly clavate capitate pale brown pigmented caulocystidia, and an absence of clamp connections.

Description:— Pileus 45–50 mm diam., hemispherical to plano-convex with a minute flattened umbo, disc somewhat rugulose; surface dull, dry, velutinous to pruinose at the disc, radiating outwards and appearing as dense pustules under a hand-lens, glabrous elsewhere; pustules dark brown (oac734–oac736), surface pallid tan (oac688– oac689). Context up to 3 mm thick, white. Lamellae free, close, with 3–4 tiers of lamellulae, some bifurcate, thin, pale pink (oac758–oac760), margin pallid tan (oac688–oac689). Stipe 45–48 × 4–5 mm, central, terete, hollow; surface dull, dry, finely fibrillose especially at the base, grayish brown fibrils over a white to off-white surface, context white. Odor indistinct. Taste indistinct.

Basidiospores 7–8 (–9) × 5–7 µm [x m = 7.8 ± 0.45 × 6.1 ± 0.52 µm, Q = 1.14–1.4, Q m = 1.28 ± 0.09, n = 50, s = 1], subglobose to broadly ellipsoid, smooth, hyaline, with a guttule, inamyloid, thick-walled. Basidia 20–36 × 5–8 µm, clavate, 4-spored, hyaline, guttulate, thin-walled, sterigmata 2–4 × 0.5–1 µm. Basidioles 15–22 × 6–8 µm, clavate, hyaline, guttulate, thin-walled. Lamellar edge sterile. Cheilocystidia 28–60 (–80) × 12–23 µm, narrowly to broadly clavate or rarely fusoid-ventricose, obtuse, with pale brown plasmatic pigment or sometimes hyaline, thin-walled. Pleurocystidia 70–98 (–103) × 15–30 µm, broadly to narrowly lageniform or sometimes fusoid, obtuse or sometimes nodulose-capitate, hyaline or occasionally with pale brown plasmatic pigment, thin-walled. Pileipellis a trichoderm to trichohymeniderm with erect fascicles, especially towards the disc, terminal elements 64–105 × 8–25 µm, clavate to cylindro-clavate or narrowly filiform, obtuse or rarely subcapitate, with pale brown plasmatic pigment or hyaline, non-incrusted, non-gelatinous, thin-walled. Pileus trama interwoven, composed of hyaline, non-gelatinous, thin-walled, clavate to inflated hyphae, 3–20 µm diam.. Lamellar trama inverse, composed of hyaline, non-gelatinous, thin-walled hyphae, 3–14 µm diam.. Stipitipellis a cutis, composed of hyaline, non-incrusted, non-gelatinous, thin-walled hyphae, 3–10 µm diam.. Caulocystidia 40–75 × 6–12 µm, uncommon, solitary to clustered, narrowly clavate to filiform, obtuse or frequently mucronate-capitate, typically with brown plasmatic pigment or hyaline, thin-walled. Clamp connections absent in all tissues examined.

Habitat and known distribution:—Gregarious on wood in subtropical montane transitionary primary to secondary broadleaf- Podocarpaceae rainforest containing Burckella obovata ( Sapotaceae ), Cryptocarya tannaensis ( Lauraceae ), Dacrycarpus imbricatus ( Podocarpaceae ), Elaeocarpus floridanus ( Elaeocarpaceae ), Ficus smithii ( Moraceae ), Hernandia moerenhoutiana ( Hernandiaceae ), Melicope sp. ( Rutaceae ), Metrosideros vitiensis ( Myrtaceae ), Meryta neoebudica ( Araliaceae ), and Neuburgia corynocarpa ( Loganiaceae ), Vanuatu (Aneityum). Also known from Chile (Juan Fernandez Islands) and Argentina.

Material examined:— VANUATU. Tafea Province: Aneityum, Nethwanethervana , 20°12.027′S, 169°47.727′E, elev. 317 m, 10 December 2019, coll. J. A . del Rosario , JAD 331 ( HAY) .

Notes:— Pluteus fernandezianus Singer (1958: 220) was originally described by Singer (1958) from the Juan Fernandez Islands located off the western coast of Chile and was placed in stirps Plautus and then in stirps Umbrosus ( Singer 1986) . According to Niveiro and Albertó (2012) the species has also been reported in Argentina by Raithelhuber (1991). A study by Menolli and Capelari (2013) of Brazilian Pluteus spp . collections by P.C. Hennings and J. Rick, concluded P. velatus Rick (1961: 417) should be considered a nomen dubium based on their observations that the type material is inconsistent with the type description. According to Menolli and Capelari, the pileus and lamellae edge color from the type description combined with their examination led them to suggest the possible identity of P. fernandezianus , however its presence in Brazil remains unconfirmed.

The Vanuatu specimen would fit well compared to the original protologue description of P. fernandezianus , but with a few caveats. The Vanuatu material displays very similar pileus features, but are larger than what was originally described by Singer. Singer (1958) noted the pileus being 14 mm broad when dried, which may lead to the assumption many of these observations were on dried material that may have been larger when fresh. Singer described the stipe as being pallid white and maybe darkening towards the base, but noted it as not being any sort of fuscous or fuliginous fibrillose, but rather somewhat pubescent-subpruinose. The Vanuatu specimen, also at first glance has an overall white stipe, however with the aid of a hand-lens it is possible to see that there are very fine grayish brown fibrils which are easily overlooked. Singer’s observations based on dried material may suggest this character is less distinctive in old material. Regarding microscopic characters, the Vanuatu specimen matches in the size and shape of the spores, and the shape and pigmentation of the pleurocystidia, cheilocystidia, and pileipellis terminal cells. The Vanuatu material’s pleurocystidia shape and apex ornamentation especially match the pleurocystidia of Singer’s Chilean material described as “…the tip sometimes short apiculate in the center, sometimes sinuate or nodulose at the apex,” ( Singer 1958). The main difference is that Singer’s specimens have slightly shorter cheilocystidia (33–48 × 8.7–19 µm) and pleurocystidia (46–65 × 8.7–23.3 µm) compared to this material. Singer also did not include caulocystidia in the original description, which may indicate re-examination of the holotype is necessary.

Menolli et al. (2015c) also acknowledged that Singer (1969) considered P. brunneoolivaceus Horak (1964: 165) a synonym of P. fernandezianus , but without elaboration. Based on a comprehensive comparison of the type descriptions of these species, Singer may have related the two due to the similarities of the basidiomes and the marginate lamellae. Horak described the pleurocystidia of P. brunneoolivaceus as having an apex “subcapitata, cornuis nullis, saepissmime verruciformibus vel digitiformibus…” ( Horak 1964) compared to Singer’s P. fernandezianus pleurocystidia being “… sometimes short apiculate in the center, sometimes sinuate or nodulose” ( Singer 1958). Based on Horak’s accompanying plate illustrations ( Tab. 1, 1a–g; Horak 1964) and a re-description of the holotype ( Horak 1980b) the pleurocystidia on P. brunneoolivaceus appear to be digitate or cornuate and have apically thickened walls similar to metuloids in sect. Pluteus , which in the protologue ( Horak 1964) are comparable to the metuloids in P. cervinus . Confusingly, in the re-description of P. brunneoolivaceus the thick-walled pleurocystidia are not mentioned but illustrated (Lamina XXV, v; Horak 1980b). Re-examinations of these type specimens in addition to analysis with molecular data are necessary to clarify the relationships between these taxa. Nevertheless, based on the type descriptions, none of these species conform with the material from Vanuatu.

Menolli et al. (2015c) tentatively identified specimen “RSPF330” deposited in the RSPF Herbarium at the Universidade de Passo Fundo in Brazil as P. cf. fernandezianus . This Brazilian collection was originally identified as P. beniensis Singer (1958: 285) , a species in sect. Celluloderma , and was revised due to their observations of a euhymeniderm pileipellis mixed with clavate-fusiform and sphaeropedunculate elements, rather than an epithelial type pileipellis. In addition, their molecular analysis placed the specimen in sect. Hispidoderma . Due to an absence of macromorphological data, they related “RSPF330” to P. fernandezianus because of the shape and pigmentation of the pleurocystidia and cheilocystidia. The combination of larger, more utriform pleurocystidia, presence of sphaeropedunculate cells in the pileipellis, and molecular data separates “RSPF330” from the Vanuatu specimen. Interestingly, in part due to molecular and morphological data, “RSPF330” may be compared to the Vanuatu collections in the following section identified as P. rimosellus Singer in Singer & Digilio (1952: 262).

Phylogenetic analysis of ITS data ( Fig. 15c ) places the Vanuatu material of P. fernandezianus sister to a recently described species from Vietnam, P. ornatus E.F. Malysheva (2023: 20) ( Malysheva et al. 2023). Both the Vanuatu specimen and P. ornatus share a superficial resemblance to the well-known species of P. umbrosus (Persoon) Kummer (1871: 98) and its allies. However, the two species can be separated due to some significant differences between them. Pluteus ornatus produces a much larger pileus (80–100 mm diam.) and stipe (70–90 × 6–13 mm). The Vanuatu material of P. fernandezianus has a stipe that is white overall with fine longitudinal gray fibrils, rather than the beigetoned stipe described in P. ornatus . Pluteus ornatus specimens also have distinctly marginate, serrate lamellae while those in the Vanuatuan P. fernandezianus have a whole margin. Micromorphologically, both specimens share the same shaped cystidia, but there are subtle significant differences. Pluteus ornatus has larger cheilocystidia (47–110 × 17– 43), and pleurocystidia with 2–4 apical excrescences compared to the seldom observed single capitate pleurocystidia in the Vanuatu material. The latter difference may be significant, but it is noteworthy that variation in this form exists within known species of Pluteus or is easily overlooked as in the instance with P. chrysaegis . However, these traits in addition to phylogenetic distance in the analyses warrants treating them as separate taxa.

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 22. Basidiome of Pluteus fernandezianus (JAD 331). Scale bar = 10 mm. Photo by: Jonathan del Rosario.

FIGURE 23. Pluteus fernandezianus. 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.