Recent taxonomic discoveries suggest a host-symbiont co-migration of Russula subsect. Castanopsidum with Fagaceae in the Americas

Abstract

Three members of ectomycorrhizal fungi belonging to Russula subsection Castanopsidum are described from neotropical montane forests dominated by species of Fagaceae in Panama and Colombia. Russula esperanzae sp. nov. from Colombia differs in the field from other members of the subsection by slender longitudinally striated red stipes as well as characteristics of spores and basidia. Russula atroamethystina subsp. atroamethystina, originally described from Costa Rica, is reported for the first time from Panama. Closely related and morphologically similar Colombian collections are described as R. atroamethystina subsp. guacahayoensis subsp. nov. and differ from the typical subspecies by longer hymenial cystidia as well as molecular sequence data. The distribution of this newly described subspecies is restricted to Fagaceae forests east of the Isthmus of Panama. This suggests an allopatric diversification, likely driven by the absence of Fagaceae in the tropical lowland forest of the Darién Gap. Russula esperanzae is exclusively associated with Trigonobalanus excelsa, a tree species of Fagaceae endemic to Colombia. The role of its association with this tree in the evolutionary history of the species is discussed. Based on molecular timing, species of the subsection Castanopsidum started to evolve approximately 15.1 M years ago (mya) and display an amphi-pacific disjunct distribution with an Asian clade that split from the American clade around 11 mya. Citation: Manz C, Ortiz-Suárez A, Adamčíková K, Looney B, Noffsinger CR, Caboň M, Hampe F, Piepenbring M, Hofmann T, Buyck B, Parra-Aldana CA, Adamčík S, Corrales A (2025). Recent taxonomic discoveries suggest a host-symbiont co-migration of Russula subsect. Castanopsidum with Fagaceae in the Americas. Fungal Systematics and Evolution 16: 181-195. doi: 10.3114/fuse.2025.16.10.

Keywords: Basidiomycota; Trigonobalanus excelsa; ectomycorrhizal diversity; evolutionary history; neotropics; new taxa.

Fig. 1.

The phylogeny of Russula subsection Castanopsidum from Bayesian and ML analyses. The main topology shown is a clock constrained tree constructed with BEAST using ITS, LSU, mcm7, rpb1, rpb2 and tef1 regions. Strongly supported nodes (BI = 1 and ML > 95) are labelled by a red circle. Bootstrap support values (ML) > 50 % and posterior probabilities (BI) > 0.95 are also provided for some nodes supported at least by one of the analyses. Vertical grey background indicates estimated evolutionary time of oak diversification (3.5 mya). The scale axis shows the estimated evolutionary time (in million years) computed under a lognormal relaxed molecular clock.

Fig. 2.

Basidiomata of studied specimens of Russula subsect. Castanopsidum. A–D. Russula atroamethystina subsp. atroamethystina. A. FH-18-145, bottom right corner: eosin red colour reaction with sulfovanillin. B. Dry material of the holotype collection (B-14600a). C. FH-18-138. D. FH-18-038. E. Russula atroamethystina subsp. guacahayoensis (Corrales850 HT). F. Russula esperanzae (Corrales883).

Fig. 3.

Hymenial elements of Russula atroamethystina subsp. atroamethystina (B-14600a HT). A. Basidia. B. Basidiola. C. Marginal cells. D. Hymenial cystidia. E. Hymenial cystidia near the lamellae edges. F. Spores as seen in Melzer’s reagent. Scale bar = 10 μm, but only 5 μm for spores.

Fig. 4.

Elements of the pileipellis of Russula atroamethystina subsp. atroamethystina (B-14600a HT). A. Hyphal terminations and primordial hyphae with contents near the pileus margin. B. Hyphal terminations and primordial hyphae with contents near the pileus centre. Asterisks (*) mark primordial hyphae observed after carbolfuchsin treatment with acid resistant incrustations. Scale bar = 10 μm.

Fig. 5.

Hymenial elements of Russula atroamethystina subsp. guacahayoensis (Corrales850 HT). A. Basidia. B. Basidiola. C. Marginal cells. D. Hymenial cystidia. E. Hymenial cystidia near the lamellae edges. F. Spores as seen in Melzer’s reagent. Scale bar = 10 μm, but only 5 μm for spores.

Fig. 6.

Elements of the pileipellis of Russula atroamethystina subsp. guacahayoensis (Corrales850 HT). A. Hyphal terminations and primordial hyphae with contents near the pileus margin. B. Hyphal terminations and primordial hyphae with contents near the pileus centre. Asterisks (*) mark primordial hyphae observed after carbolfuchsin treatment with acid resistant incrustations. Scale bar = 10 μm.

Fig. 7.

Hymenial elements of Russula esperanzae (Corrales884). A. Basidia. B. Basidiola. C. Marginal cells. D. Hymenial cystidia. E. Hymenial cystidia near the lamellae edges. F. Spores as seen in Melzer’s reagent. Scale bar = 10 μm, but only 5 μm for spores.

Fig. 8.

Elements of the pileipellis of Russula esperanzae (Corrales884). A. Hyphal terminations and primordial hyphae with contents near the pileus margin. B. Hyphal terminations and primordial hyphae with contents near the pileus centre. Asterisks (*) mark primordial hyphae observed after carbolfuchsin treatment with acid resistant incrustations. Scale bar = 10 μm.