Pluteus vanuatuensis f. ramacystidiatus, 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 : 26-29

Pluteus vanuatuensis f. ramacystidiatus J.A. del Rosario & B.A. Perry, f. nov. ( Figs. 9 , 10 )

MycoBank no.:—854230

Holotype:— VANUATU. Tafea Province: Tanna between Ienehepe and Lighthouse, along banks of Numdretum River , 19°38.558′S, 169°25.713′E, elev. 286 m, 29 August 2018, coll. J. A. del Rosario, JAD 159 ( HAY).

Etymology:— rama ( L.) = branch, cystidiatus ( L.) = cystidia; refers to the branching apices on the pleurocystidia.

Diagnosis:— Pluteus vanuatuensis f. ramacystidiatus is characterized by a glabrous and sulcate grayish brown pileus with a dark grayish brown rugose disc, and a white with fine pale brown fibrils hollow stipe with a subbulbous base. When disrupted, the tissues turn faintly grayish blue. Microcharacters include subglobose spores (7.4 × 6.4 µm), four or single-spored basidia, clavate cheilocystidia, fusoid, thick-walled pleurocystidia with variable apices being acute, hooked, or irregularly polychotomous branched, similar intermediate thinner-walled pleurocystidia with lateral hooks, an ixo-cutis pileipellis with brown plasmatic contents, and an absence of caulocystidia. Clamp connections are common in all tissues. It is differentiated from P. vanuatuensis which has a distinct floccose disc, lacks elongated branched pleurocystidia, and lacks lateral hooks on the intermediate pleurocystidia.

Description:— Pileus 30–40 mm diam., convex to hemispherical, with a slight umbo, disc rugose-warted, margin sulcate; surface pellucid-striate up to half-way from margin, hygrophanous, semi-viscid, glabrous; disc/warts dark gray-brown (oac639–oac641), surface grayish brown (oac646–oac648) with patches pale pink (oac674–oac676), margin slightly paler gray-brown (oac662). Context up to 5 mm thick, pale gray-brown (oac662). Lamellae free, moderately close with 3–4 tiers of lamellulae, thin (<1 mm thick), pale pink, margin somewhat paler. Stipe 25–35 × 3–4 mm, central, terete, cylindrical above a subbulbous base, hollow; surface dull, dry, fibrous, white to cream white with minute pale gray fibrils. Tissues turning bluish gray when damaged or handled. Odor indistinct. Taste indistinct.

Basidiospores 6–8 (–9) × 5–8 µm, [x m = 7.44 ± 0.78 × 6.38 ± 0.83 µm, Q = 1–1.6, Q m = 1.17 ± 0.2, n = 50, s = 1], globose to subglobose, smooth, hyaline, with a guttule, inamyloid, thick-walled. Basidia 16–30 × 8–10 µm, clavate, 4- spored or 1-spored, guttulate, hyaline, thin-walled, sterigmata 1.5–3 × 0.5–1 µm. Basidioles 12–20 × 5–10 µm, clavate to cylindro-clavate, hyaline, thin-walled. Lamellar edge sterile. Cheilocystidia 20–80 × 12–18 µm, clavate to cylindro-clavate, or occasionally fusoid-ventricose to narrowly utriform, obtuse or occasionally capitate-umbonate, occasionally with a guttule, hyaline, thin-walled. Pleurocystidia; primary pleurocystidia 50–130 × 10–40 µm, fusoid to narrowly lageniform, or cylindro-clavate, apex variable, obtuse without outgrowths, corniculate or occasionally cornuate with 2–4 (–5) whole to bifid, acute to blunt, straight or recurved poorly or well-developed apical hooks, irregularly branched with 2–4 polychotomous branches, or sometimes bifid with 1–3 straight or recurved poorly or well-developed apical hooks per arm, majority with a guttule, hyaline, basally to apically or evenly thick-walled (up to 3 µm thick) to thin-walled; intermediate pleurocystidia 50–87 × 16–18 µm, fusoid to narrowly lageniform, apex variable, obtuse, acute, rarely mucronate, seldom irregularly branched, or cornuate with whole or rarely bifid, straight or recurved poorly or well-developed apical hooks, occasionally with 1–2 lateral projections, some with a guttule, hyaline, thin to evenly or centrally thick-walled. Pileipellis an ixo-cutis of repent hyphae embedded in a gelatinous matrix, composed of hyaline or with brown plasmatic pigment, non-incrusted, gelatinized or not, thin-walled, cylindrical hyphae, 5–24 µm diam.; terminal cells 35–135 × 3–19 µm, repent to suberect towards the disc, clavate to cylindro-clavate, obtuse, rarely with tapering apices. Pileus trama interwoven, composed of hyaline, non-gelatinous, thin-walled, clavate to inflated hyphae, 5–38 µm diam.. Lamellar trama inverse, composed of hyaline, non-gelatinous, thin-walled hyphae, 4–18 µm diam.. Stipitipellis a cutis, composed of hyaline, non-incrusted, non-gelatinous, thin-walled hyphae, 4–24 µm diam.. Caulocystidia absent. Clamp connections present in all tissues examined.

Habitat and known distribution:—Gregarious on well-decayed wood in subtropical lowland mixed-use agro tree garden and secondary broadleaf rainforest containing Bischofia javanica ( Phyllanthaceae ), Burckella obovata ( Sapotaceae ), Claoxylon gillisonii ( Euphorbiaceae ), Dendrocnide latifolia ( Urticaceae ), Didymocheton spp . ( Meliaceae ), Ficus spp . ( Moraceae ), Garcinia pseudoguttifera ( Clusiaceae ), Homolanthus nutans ( Euphorbiaceae ), Macaranga dioica ( Euphorbiaceae ), and Syzygium nomoa ( Myrtaceae ), Vanuatu (Tanna).

Material examined:— VANUATU. Tafea Province: Tanna between Ienehepe and Lighthouse, along banks of Numdretum River , 19°38.558′S, 169°25.713′E, elev. 286 m, 29 August 2018, coll. J. A . del Rosario , JAD 159 ( HAY) .

Notes:— Pluteus vanuatuensis f. ramacystidiatus closely resembles the preceding newly described species, P. vanuatuensis , but has distinct morphological features that warrant treating it as a separate taxonomic unit. Notably, the pleurocystidia in JAD 159 display the same variation of apical ornamentation seen in all collections of P. vanuatuensis , but also contain a distinct type with elongated extensive branching elements. Phylogenetic analysis of ITS data sampling the albostipitatus / salicinus clade ( Fig. 6b ) places JAD 159 sister to collections JAD 160, JAD 215, and the Vietnamese P. sp. 1 within the P. vanuatuensis clade with moderate support ( BS 79 %, PP 0.99) and identical internal topology compared to the broad sampled sect. Pluteus analysis ( Fig. 1c ). An identical sampling of taxa from this ITS analysis of the albostipitatus / salicinus clade using tef1 data ( Fig. 6c ) collapses the internal branches of the P. vanuatuensis clade and unites all these collections, including JAD 159. An analysis of this two-gene data ( Fig. 6a ) with additional sampling of the albostipitatus / salicinus clade retrieves the internal branch topology of the P. vanuatuensis clade similar to the single gene ITS analysis ( Fig. 6b ) with JAD 159 on a long branch in both the likelihood and Bayesian analyses being in a weakly supported clade with the Vietnamese P. sp. 1, JAD 160, and JAD 215 ( BS 33 %, PP 0.71). Based on the two-gene analysis, the phylogenetic affinity of JAD 159 indicates it to be P. vanuatuensis . Overall, the glabrous pileus, intermediate pleurocystidia with lateral hooks, and elongated, extended branching pleurocystidia show clear morphological differences in this single collection. These distinctive features, especially the elongated branching pleurocystidia that are rare in Pluteus , justify recognition of this specimen as a distinct form of P. vanuatuensis . It may well be that P. vanuatuensis is a highly variable morphological species, and it remains to be determined if this pleurocystidia type is exclusive to glabrous forms such as JAD 159.

Figures

FIGURE 1a–d. Maximum Likelihood phylogeny of sect. Pluteus based on ITS sequence data (-lnL = 6609.645735). 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 6a–c. Maximum Likelihood phylogenies of the albostipitatus/salicinus clade based on combined (Fig. 6a; -lnL = 4927.663337), ITS (Fig. 6b; -lnL 2206.25101), and tef1 (Fig. 6c; -lnL = 2099.291416) sequence data. 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 9. a. Basidiomes of Pluteus vanuatuensis f. ramacystidiatus in situ (JAD 159 holotype). b. Basidiomes of Pluteus vanuatuensis f. ramacystidiatus (JAD 159 holotype). Scale bar = 10 mm. Photos by: Jonathan del Rosario.

FIGURE 10. Pluteus vanuatuensis f. ramacystidiatus. a. Basidiospores. b. Basidia. c. Basidioles. d. Pileipellis terminal elements. e. Cheilocystidia. f. Intermediate pleurocystidia. g. Primary pleurocystidia. Scale bar = 10 µm. Drawings by: Jonathan del Rosario.