Lilliput brittlegill (Russula lilliputia) and Pakaraimaea brittlegill (Russula pakaraimaeae)

NEWS - Two new species of Russula from Guyana with small basidiomata: lilliput brittlegill (Russula lilliputia) and Pakaraimaea brittlegill (Russula pakaraimaeae) found in association with the hosts Dicymbe altsonii and Pakaraimaea dipterocarpacea were identified as new species based on a combined approach of morphological characterization and molecular analysis.

Ectomycorrhizal fungi (ECM) have historically been considered underrepresented in Neotropical forests, however, pockets of forest occupying the white sands region of the central Guiana Shield of Guyana are dominated by leguminous ECM trees that support an extraordinary diversity of fungi.

Russulaceae comprise the largest number of species in this region. The discovery of two new species of Russula expands our understanding of fungal diversity and the genus Russula in particular, along with the biogeography and ecosystem dynamics of often undercollected tropical forests.

R. lilliputia has small basidiomata and a fruiting habit that reaches 1.5 meters high on tree trunks, making it an exceptional fungus. The species complex of R. annulata and R. radicans in Africa is known as "lilliputiennes" because of its small size, but the basidiome of R. lilliputia is much smaller, possibly the smallest Russula ever described.

This species is characterized by a very small red pileus, not exceeding 5 mm, a solid stipe with pruinose and pileus when dry, production of basidiomes on the stem surface of D. altsonii, spores with indistinct suprahilar plage, sparse and low interconnections between verrucae, long hair-like pileocystidia arising from the epithelioid layer of swollen cells and a white spore cast.

R. lilliputia is known from only one large collection, the Upper Potaro Basin of Guyana. The type collection consists of all stages of basidiome development including about 30 individual basidiomata and primordia spread over an area of 0.5 m2 of stem surface.

R. pakaraimaeae is characterized by a 5-17 (25) mm pileus, occurring in the Upper Mazaruni Basin of Guyana in marginal forests around the Pegaima savanna in association with P. dipterocarpaceae and possibly D. jenmanii, fruiting habit with a single branching or rhizoidal base attached to large fallen leaves and organic debris. The species is solitary or in small groups in December.

Pileus dark red to purple-brown with pruinose white margins when young, stipe thick when wet then with prominent fibrillar squamules often pink when dry, spores isolated verrucous without interconnection and distinct suprahilar plage sometimes forming a partial collar on the apicululus, long hair-like pileocystidia arising from scattered swollen cells.

Original research

Steven L. Miller, M. Catherine Aime & Terry W. Henkel (2024). Russulaceae of the Pakaraima Mountains of Guyana 5. Two newly described diminutive species in a novel lineage of the crown clade of Russula (Russulaceae), Phytotaxa 668 (2): 117–129, DOI:10.11646/phytotaxa.668.2.1

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