Russula ferruginea Corrales & Vera 2022, sp. nov.
Creators: name: Buyck, Bart
name: Eyssartier, Guillaume
name: Armada, François
name: Corrales, Adriana
name: Hembrom, Manoj Emanuel
name: Rossi, Walter
name: Bellanger, Jean-Michel
name: Das, Kanad
name: Dima, Bálint
name: Ghosh, Aniket
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Fungi
Basidiomycota
Agaricomycetes
Russulales
Russulaceae
Russula
Russula ferruginea

description: 118. Russula ferruginea Corrales & Vera, sp. nov.
(Figs 16A; 17-20)
DIAGNOSIS. — R. ferruginea sp. nov. differs from the European R. praetervisa Sarnari or the North American R. amerorecondita Avis & Barajas in the combination of the relatively delicate stature, dark brown pileus centre contrasting to its pale yellowish brown margin, almost mild taste and especially its conspicuous color change from light brown to reddish brown or rusty on wounded places especially apparent on the stipe base and the lamellae. It is defined also by combination of narrow hymenial cystidia up to 8 µm and spores with warts connected by fusions and short fine lines.
HOLOTYPE. — Colombia. Cundimarca Depart., Mosquera, Chicaque Natural Reserve, 4°36’22”N, 74°18’17”W, alt. 2130 m, in forest dominated by Quercus humboltii, terrestrial, 17.X.2019, A. Corrales 944 (HUA, SAV).
MYCOBANK. — MB841769.
GENBANK. — MZ604288 (ITS), MZ604283 (nrLSU), MZ553923 (rpb2), MZ553926 (tef1 α), all from holotype.
ETYMOLOGY. — The name refers to reddish spots on the base of the stipe and colour change of the wounded context from light brown to reddish brown, resembling iron rusting.
ADDITIONAL MATERIAL STUDIED. — Colombia. Cundimarca Depart., Mosquera, Chicaque Natural Reserve, 4°36’22”N, 74°18’17”W, alt. 2130 m, in forest dominated by Quercus humboltii, terrestrial, multiple collections of different mycelia distant approximately hundred meters apart, 17.X.2019, A. Corrales 914, A. Corrales 935, A. Corrales 1019 (all deposited in HUA).
SPECIMENS STUDIED FOR COMPARISON. — Russula austromontana (Singer B 12402 (F), holotype); Russula cf. austromontana / crucensis: Costa Rica, 3.5 km W of Empalme, 2200 m asl., in montane Quercus seemannii forest, 2.VI.2001, leg. B. Buyck, BB 01.023 (PC); ± 5 km SW of Cerro de la Muerte, Albergue de la Montana, Savegre, 2200 m asl., in montane Quercus seemannii forest, 6.VI.2001, leg. B. Buyck, BB 01.076 (PC).
DESCRIPTION
Pileus
Small to medium sized, 24-48 mm in diam., when young convex, mature plane with depressed centre; margin strongly tuberculate-striate to c. half of the radius (7-13 mm); cuticle slimy especially near the center, shiny, margin peeling or radially cracking, color near margin light brown turning to light yellowish brown or beige, near the center dark brown, deep blackish brown to almost black, discoloring to yellowish brown.
Lamellae
Moderately distant, c. 8-12/ 1 cm near the pileus margin, 1.5-4 mm broad, pale yellowish-brownish to almost white, lamellulae rare, furcations frequent especially near the stipe, edge even and concolorous.
Stipe
28-33 × 5-7.4 mm, cylindrical and staight, longitudinally striate, light brown, darker and with reddish spots at the base, cortex 1-2 mm thick, interior cavernate.
Context
2-3 mm thick at the middle of the pileus radius, fragile, light brown, flesh turning reddish brown when cut and getting more red spots at the base when bruised, taste slightly bitter and spicy, odour fishy and fetid.
Spore print
Not observed.
Spores
(6.4-)6.8-7.5-8.1(-8.6) × (5.4-)5.7-6.2-6.7(-7) µm, subglobose to broadly ellipsoid Q = (1.07-)1.13-1.21-1.28(-1.34); ornamentation of moderately large, moderately distant [(4- 7(-8) in a 3 µm diam. circle] amyloid, obtuse warts, (0.3)0.4- 0.8(-1) µm high, mainly fused in small groups or short chains ([0-]1-4[-5] fusions in the circle), connected by occasional and usually short line connections ([0-]1-3[-5] in the circle); suprahilar spot not amyloid, relatively large, smooth or covered by few small low warts.
Basidia
(22-)35-43.7-53 × (5.5-)7-9.2-11(-12) µm, narrowly clavate, ocassionally pedunculate, 4-spored; basidiola cylindrical or clavate, c. 5-9 µm wide.
Hymenial cystidia
Mostly numerous, c. 1800-2100/mm2, (50-)56-67.8-79(- 86) × 6-7.1-8(-9) µm, mainly fusiform or lancelolate, rarely narrowly langeniform or subcylindrical, apically mainly acute and sometimes pointed, occasionally obtuse, often moniliform, mainly with small, pearl-like, 1-3(-6) µm long appendage, thin-walled; contents weakly heteroformous, with fine, dispersed granulations usually near the apex, sometimes optically empty, often in Congo red with pale yellow pigment, turning almost black in sulfovanillin; near the lamellae edges smaller, (35-)38-48.4-58(-66) × 6-6.8-8µm, similar in shape and contents.
Marginal cells
Similar to basidiola but smaller, (12-)14-17-20(-21) × 5-6.5- 7.5 µm, cilindrical or clavate, apically obtuse, mixed with occasional basidia.
Pileipellis
Orthochromatic in Cresyl Blue, sharply delimited from the underlying context, 150-240 µm deep; suprapellis strongly gelatinized, verrucose-bumpy in vertical section, irregularly 15-35 µm deep, composed of more or less repent, loose or clustered hyphae; gradually passing to 120-220 µm thick subpellis formed by loose, gelatinised, irregularly oriented but near trama horizontally oriented, dense, 2-4 µm wide hyphae.
Acid-resistant incrustations
Absent.
Hyphal terminations
Near the pileus margin composed mainly of one or two cells, flexuous,thin walled, frequently branched, occasionaly nodulose or angulose; terminal cells (9-)12.5-19.7-27(-34) × 2.5-3.8-5(- 5.5) µm, mainly cylindrical or clavate, often apically obtuse and sometimes slightly narrowed; subterminal cells usually as wide as long, frequently branched or with lateral projections.Hyphal terminations near the pileus centre similar, (12-)14-23.8-33(- 41) × 3-4.3-5(-6) µm, more frequently angulose-nodulose.
Pileocystidia
Near the pileus margin always 1-celled, subulate, narrowly fusiform or lancelolate, variable in length and often long and originating deep in the subpellis, thin-walled, (24-)29-40.4- 51(-76) × 3-4.2-5 µm, apically mainly acute, with a small appendage or knob; contents dispersed, finely granulous, weakly greying in sulfovanillin. Pileocystidia near the pileus centre similar in shape but usually shorter (22-)28-36.6- 42.5(-47) × (3-)3.6-4.4-5.2(-6.5) µm, more frequently apically constricted than acute, with contents located in diverse places, usually in apical parts.
Cystidioid hyphae
Dispersed in subpellis but more frequent near the context, sometimes similar to cystidia but longer, contents often more conspicuous, oleipherous and turning dark brown in sulfovanillin and red after carbolfuchsin treatment.
Clamp connections
Absent from all tissues.
NOTES
The multilocus phylogenetic reconstruction based on nrLSU, rpb2 and tef1 α (Fig. 5) clearly places our Colombian and Panamanian collections in one monophyletic clade with strong support values concerning bootstrap (MLbs = 100 %) and Bayesian posterior probability (BPP = 1). This clade is recognised in this study on the rank of species as R. ferruginea sp. nov. It belongs to section Ingratae Quél. of the subgenus Heterophyllidinae Romagn. The rusty-spotted North American R. pulverulenta Peck is the sister species of R. ferruginea sp. nov. (MLbs = 61 %, BPP = 0.96), although with poor support. The collection BPL276, labelled as R. pectinatoides Peck, is placed on the higher rank node with moderate support (ML = 68, BI = 0.96). In the ITS analyses (see sample with GenBank accession number KT 933975 in Fig. 6), however, this collection forms part of the species clade of R. amerorecondita.
Because sequence data are not yet available for many species of the section Ingratae, our multilocus analysis is undersampled. To trace close relationships and to eliminate coidentity with some taxa published earlier, we analysed also the ITS region based on a set of sequences (Fig. 6) representing the described diversity of American species of the section Ingratae. The topology of this tree is not consistent with the topology obtained in the multilocus analyses and good bootstrap support is usually limited to terminal nodes. Russula ferruginea sp. nov. is placed in a strongly supported clade on a long branch, but there is no support for a more precise placement within the section Ingratae. Colombian and Panamanian collections of the new species received good support (MLbs = 97% and MLbs = 94 % respectively), but they are recognised on the rank of subspecies as discussed below (see comment under subsp. panamensis).
The field appearance of R. ferruginea sp. nov. with a relatively fragile stature, dark brown pileus centre contrasting to its pale yellowish brown margin and almost mild taste resembles the European species R. praetervisa or the North American R. amerorecondita. A remarkable feature of R. ferruginea sp. nov. is its conspicuous color change, of the trama becoming reddish brown or rusty on wounded places, especially apparent at the base of the stipe and at the lamellae. This distinct rusty aspect of bruised surfaces is known in several other species of Ingratae such as R. illota Romagn. or R. pulverulenta. With different intensity, however, this color change also occurs in many other species of Ingratae.
Among the 78 Russula species described from Latin America (Vera et al. 2021), only some are known from subtropical and tropical montane oak forests and, among these, four are described from Costa Rica as members of the section Ingratae: R. arcyospora Singer, R. austromontan a Singer, R. crucensis Gómez and Alfaro and R. quercusoleoideis Singer et al. Russula arcyospora is similar to R. foetens Romagn. but has odour components of bitter almond and a prominent spore ornamentation composed of high ridges (Singer 1990). Russula austromontana (Singer 1989) is similar to R. ferruginea sp. nov., but has broader hymenial cystidia and more prominent spore ornamentation composed of mostly isolated warts, according to our personal (BB) observations of the type. We sequenced two recent collections collected at or near the type locality in Costa Rica with macroscopical and microscopical characteristics similar to the type collection of R. austromontana. These specimens proved to be unrelated to R. ferruginea sp. nov. in our phylogeny. Russula crucensis, originally classified in sect. Pellicullariae R. Heim subsect. Discopodinae R. Heim, is another member of the section Ingratae (Buyck 1992) and differs from R. ferruginea sp. nov. exactly in the same features as R. austromontana, from which it is difficult to distinguish at this moment. R. quercusoleoideis was originally placed in sect. Ingratae (Singer et al. 1983), but according to Buyck (1992) it is a member of subsect. Griseinae Jul. Schäff. and both, pileipellis structure and hymenial cystidia, are different from the corresponding structures in R. ferruginea sp. nov.
description: Published as part of Buyck, Bart, Eyssartier, Guillaume, Armada, François, Corrales, Adriana, Hembrom, Manoj Emanuel, Rossi, Walter, Bellanger, Jean-Michel, Das, Kanad, Dima, Bálint & Ghosh, Aniket, 2022, Fungal biodiversity profiles 111 - 120, pp. 23-61 in Cryptogamie, Mycologie 20 (2) on pages 43-44, DOI: 10.5252/cryptogamie-mycologie2022v43a2, http://zenodo.org/record/7828891