Lactifluus umbilicatus Silva-Filho, D.L.Komura & Wartchow, 2020

Silva-Filho, Alexandre G. S., Sá, Mariana C. A., Komura, Dirce L., Moncalvo, Jean-Marc, Margaritescu, Simona, Roy, Mélanie & Wartchow, Felipe, 2020, Two novel species of Lactifluus subg. Pseudogymnocarpi (Russulaceae) from Brazil, Phytotaxa 436 (3), pp. 222-236 : 224-227

Lactifluus umbilicatus Silva-Filho, D.L.Komura & Wartchow , sp. nov. ( Figs. 2–3–6a )

Mycobank:—MB832851

Genbank accession nrITS: MK929291

Type:— BRAZIL. Pará: Belterra, Floresta Nacional do Tapajós, Trilha da Comunidade Maguari, 2°48’14” S, 54°59’50” W, on soil close to Tachigali myrmecophila , 30 March 2014, D.L. Komura, T.S. Cabral, I.R. Fonseca DLK1964 (INPA 284001 holotype, JPB 64507 isotype).

Diagnosis:—Distinguished from other species by: pileus umbilicate, orange, surface slightly wrinkly, margin slightly striate; lamellae slightly decurrent and whitish; stipe orange. Basidiospores 7–8.5 × 6–7 µm; ornamentations up to 1 µm high, composed of irregular short warts connected by fine lines; pseudocystidia absent; macrocystidia (pleuro- and cheilo-) fusoid to slightly fusiform; pileipellis a lampropalisade with frequent to abundant thick-walled terminal elements and frequent to abundant lactifers, and a unique ITS sequence.

Description:—Pileus 55–63 mm diam., plane convex, umbilicate, dark orange (5A8), brownish orange (5C6) to grayish orange (6B7); surface slightly wrinkly, dry, slightly opaque; margin slightly striate, straight to decurved; edge sometimes entire, sometimes eroded ( Figs. 2a–d ); context firm, 4–6 mm at the disc to very thin towards margin, light orange (5A4), unchanging. Lamellae short decurrent, distant, white (1A1) to yellowish white (1A2); edge even, concolorous with the face; lamellulae frequent, with three lengths ( Figs. 2b–c ). Stipe 35–41 × 6–9 mm, central, cylindrical, equal to slightly tapered towards the base, dry, light orange (5A4/5) to orange (5A6); surface smooth, slightly ribbed ( Figs. 2b–c ); context solid. Veil absent. Latex not found. Odor and taste not determined.

Basidiospores 7–8.5(–9) × (4–)6–7 µm; L = 7.5 µm, W = 6.2 µm; Q = 1.14–1.26, Qm = 1.21; subglobose to broadly ellipsoid; predominantly broadly ellipsoid, thin-walled, hyaline, ornamentation amyloid, up to 1 µm high, composed of irregular short warts connected by fine lines, not forming a complete reticulum; plage non-amyloid; hilar appendix up to 3.5 µm long, inamyloid ( Figs 3a , 6a ). Basidia 53–64 × 7‒10 µm, cylindrical, slightly clavate, sometimes slightly fusiform, 1–2- and 4-spored, predominantly 4-spored, thin-walled, hyaline, sometimes with refractive contents; sterigmata up to 7 µm long ( Fig. 3b ). Pleuromacrocystidia abundant, 55–75 × 7–10 µm, fusoid to slightly fusiform, thin-walled, with refractive contents, projecting up to 10 µm above the hymenium ( Fig. 3c ). Pleuropseudocystidia absent. Lamella edge sterile, composed of abundant cheilomacrocystidia and marginal cells: cheilomacrocystidia 45–52 × 6–8 µm, fusoid to slightly fusiform, thin-walled, with refractive contents ( Fig 3d ); marginal cells 10–30 × 4–7 µm, cylindrical to clavate, thin-walled, hyaline. ( Fig. 3f ). Hymenophoral trama composed of abundant sphaerocytes, 11–33 µm diam. and scattered lactifers, 7‒10 µm diam., thin-walled. Subhymenium cellular. Pileipellis a lampropalisade up to 75 µm thick, consisting of a layer of isodiametric cells with frequent to abundant lactifers and frequent to abundant thick-walled elements ( Fig. 3h ): isodiametric cells, 7–17 µm diam., thin-walled; lactifers 7‒13 µm diam, thin-walled, with refractive contents, sometimes emergent, arising deeply from pileus trama, clinal to oblique oriented ( Figs. 3e,h ); thick-walled terminal elements 37–98 × 3–6 µm, aciculate, filiform, cylindrical, sometimes flexuous, sometimes septate, sometimes forked, thick-walled (up to 2 µm thick), hyaline, clinal to oblique oriented ( Figs. 3g,h ). Pileus trama composed of abundant sphaerocytes 9–30 µm diam., thin-walled, cylindrical 2‒4.5 µm wide hyphae, and frequent, thin-walled, 7–12 µm wide lactifers. Stipitipellis a lampropalisade similar to pileipellis. Clamp connections absent from all tissues examined.

Etymology:—From Lat. ‘umbilicatus’. In reference to the umbilicate pileus.

Habitat:—Scattered, on clay soil in dense ombrophilous forest in Amazon, close to Tachigali myrmecophila ( Fabaceae ).

Distribution:—Known only from type locality.

Additional material examined:— Lactifluus amazonensis : Brazil. Amazonas: Manaus, Manaus-Caracaraí road, km 125, 20 July 1978, R. Singer B11315 (holotype INPA 82756).

Comment:— Lactifluus umbilicatus belongs to Lf. subg. Pseudogymnocarpi ( De Crop et al. 2017) based on both molecular and morphological evidence, such as: its orange pileus color, unchanging context and the lampropalisade structure of the pileipellis. Phylogenetic analysis places the species in Lf. sect. Polysphaerophori, a clade/section composed of Neotropical entities, but not yet characterized morphologically.This new species clusters with Lf. ceraceus from French Guiana and two undescribed species (Th678) from Guyana and (AMV1874) from Colombia respectively. Despite being phylogenetically closely related, Lf. ceraceus has a more robust basidiomes, (pileus 64–98 mm diam., and stipe 83–112 × 18–26 mm), smaller basidiospores (5.4–8.1 × 4.4–6.2 μm), smaller thick-walled elements on the pileipellis (8–42 × 3.5–6 μm) that are predominantly cylindrical or subclavate and it lacks lactifers on the pileipellis ( Crous et al. 2017).

Also related are ‘ Lactarius pegleri ’, a species from Martinique, still to be recombined into Lactifluus , and Lf. veraecrucis from Mexico. These two species have similar basidiospore sizes, but ‘ Lactarius pegleri ’ has more fragile basidiomata, with a smaller pileus (25–57 mm in diam.) and shorter stipe (25–38 mm long), and absence of true pleurocystidia ( Lalli & Pacioli 1992); Lactifluus veraecrucis differs in the smaller pileus (25–45 mm diam.), lower basidiospore ornamentation (up to 0.5 µm high), shorter thick-walled elements in the pileipellis (20–44 × 2.5–5.5 µm) and thick-walled isodiametric cells in the pileipellis ( Montoya et al. 1996).

Lactifluus amazonensis , Lf. brasiliensis and Lf. rupestri s also have an yellowish to orange pileus, unchanging context and latex and a trichoderm to (lampro)palisade pileipellis, suggesting the placement of these species in Lf. subg. Pseudogymnocarpi ( De Crop et al. 2017). Molecular data for these taxa are not yet available. Lactifluus amazonensi s is the only species that has thick-walled elements in the pileipellis, similar to those of Lf. umbilicatus , differing in more fragile basidiomata with smaller pileus (33–45 mm diam.) and shorter stipe (19–48 mm length) ( Singer et al. 1983). In addition, we analyzed the holotype (R. Singer B11315), which exhibits larger (8.5–10.5 × 7–8.0 μm) and predominantly subglobose basidiospores, abundant cylindrical to subclavate thick-walled elements in pileipellis and absence of lactifers in the pileipellis (see in Silva-Filho & Wartchow 2019, p. 219).

Figures

FIGURE 2. Lactarius umbilicatus. a–d D.L. Komura 1964 (holotype). a) basidiomata in situ, b–d) basidiomata ex sito. (bars = 10 mm). Photos by: Dirce L. Komura.

FIGURE 3. Lactifluus umbilicatus. a–h D.L. Komura 1964 (holotype). a) basidiospores b) basidia, c) pleuromacrocystidia, d) cheilomacrocystidia, e) lactifers of the pileipellis, f) marginal cells of the lamellar edge, g) thick-walled elements of the pileipellis, h) pileipellis. (bars = 10 μm). Drawings by:Alexandre G. S. Silva-Filho.

FIGURE 4. Lactarius venosellus. a M.C.A. Sá MS 37 (holotype), b,c F. Wartchow 15/2017 (Paratype). a) basidiomata in situ, b,c) basidiomata ex situ (bars = 10 mm). Photos: a) Mariana C. A. Sá. b) Felipe Wartchow.

FIGURE 5. Lactifluus venosellus. a–g M.C.A. Sá MS 37 (holotype). a) basidiospores b) basidia, c) pleuropseudocystidia, d) cheilopseudocystidia,, e) marginal cells of the lamellar edge, f) lactifers of the pileipellis, g) pileipellis. (bars = 10 μm). Drawings by: Alexandre G. S. Silva-Filho

FIGURE 6. SEM micrographs of the basidiospores. a), Lactifluus umbilicatus (D.L. Komura 1964 holotype); b,c) Lactarius venosellus (M.C.A. Sá MS 37 holotype). (bars = 2 μm).