Bolbitius is a genus of small, fragile mushrooms that many casual hikers have probably walked straight past. The mushrooms are famously short-lived, with thin, often viscid caps that bear a striate margin, free gills, and a tendency to deliquesce as they mature. According to Index Fungorum, the genus currently holds around 124 name records, but after years of reclassification into related genera such as Conocybe and the recently separated Conobolbitina, only about 70 species are accepted today. Distinguishing one Bolbitius from another is notoriously difficult, and the boundaries of several species complexes remain ambiguous even to specialists.

The new research, led by Tolgor Bau and Hong Cheng and based at Jilin Agricultural University, combined classical morphology with molecular phylogenetics to untangle the genus in northeast China. Specimens were collected in recent years from broad-leaved and mixed forests, with one additional collection from Yunnan Province, then dried at 50 degrees Celsius and deposited in the university’s fungarium. The researchers documented the colour, size, substrate and ecology of fresh specimens in the field, and followed standardised colour charts for their descriptions.

On the molecular side, the team extracted DNA from the dried specimens and sequenced three genetic regions: the internal transcribed spacer, or ITS; the nuclear large subunit, nrLSU; and the translation elongation factor 1-alpha gene, tef1-alpha. These three loci are the standard workhorses of fungal taxonomy, and combining them produces far more reliable species trees than any single marker. The team aligned 75 ITS, 56 nrLSU and 28 tef1-alpha sequences downloaded from GenBank alongside their own new sequences, refined the alignments, and used Maximum Likelihood and Bayesian methods to reconstruct the evolutionary history of the group.

The resulting dataset spanned 2,358 aligned base pairs across 75 taxa and revealed that Bolbitius splits into three major clades. Two of those clades contained the Chinese specimens, and the placement of each new species proved robust even when the researchers repeated the analyses with reduced datasets to check that missing sequences for some reference material were not skewing the results. The two new species emerged as clearly separate lineages, each supported by both DNA and distinctive anatomy.

The first of the newcomers, formally named Bolbitius planoflavus, was collected on Laobai Mountain in Jilin Province at an altitude of just 273 metres. Its name literally means flat and yellow, and that is exactly what it looks like: as the cap matures it becomes distinctly applanate, or flattened, in a pale pastel yellow, unlike most yellow-capped relatives that retain a convex shape. Under the microscope, the species produces ellipsoid to oblong spores measuring roughly 9 to 10.5 micrometres long with a distinct germ pore, and, unusually for the genus, occasionally produces basidia bearing only two spores instead of the usual four. It grows solitarily on rotten leaves and deeply decayed wood in oak-dominated forests, fruiting in summer, and is currently known only from Jilin. Its closest relative in the DNA analysis was the Vietnamese species Bolbitius aurantiorugosus, but the ITS sequences share only 95.24 percent identity, well outside the range of a single species.

The second new species, Bolbitius fuscopapillatus, comes from Chenjiadian Forest Farm in Heilongjiang Province and carries one of the more evocative names in recent mycological literature. Its cap bears a violet-brown papillate umbo, a small raised button at the centre that stands out darker than the rest of the cap, while the purplish-white margin carries faint whitish veil remnants, the traces of a partial veil that soon disappears. The species is consistently four-spored, has smaller spores than its lookalike Bolbitius reticulatus, and, unlike that species, completely lacks clamp-connections, the small loop-shaped structures that some fungi form at the junctions of their hyphal cells. Notably, an unnamed Bolbitius sequence sampled in Chile via a citizen-science platform turned out to share 99.72 percent of its ITS sequence with the new species, hinting that the fungus may have a far wider, if so far undocumented, distribution.

Alongside the two novelties, the study reports Bolbitius bisporus as a new record for China, found in two forest parks in Jilin Province. This species was originally described from Russia, and the Chinese collections differed from the Russian holotype mainly in having somewhat smaller spores. But the key diagnostic character, predominantly two-spored basidia, was retained, and the Chinese ITS sequences matched the holotype with 99.85 percent similarity, differing by just a single nucleotide. The authors interpreted the spore size difference as intraspecific variation, a conclusion that shows how molecular data can settle disputes that pure morphology leaves open.

Perhaps the most intriguing finding is a pattern linking evolutionary history to anatomy. Species in Clade A, including Bolbitius planoflavus, have a relatively homogeneous cap skin made up of clavate, colourless to pale yellowish cells, whereas species in Clade B, including Bolbitius fuscopapillatus and Bolbitius bisporus, have cap skins composed of two distinct cell types loaded with dark purple intracellular pigments. If this correlation holds up as more taxa are sampled, it could provide mycologists with a visible anatomical signature of deep evolutionary splits within the genus. The authors caution, however, that the trend was observed across only a limited number of taxa and needs broader testing.

The study also highlights how much work remains. Both new species are known from only two collections each, and no reliable infrageneric classification of the genus currently exists; earlier proposals for splitting Bolbitius into sections rest on morphological traits whose distribution conflicts with the new molecular trees. The authors argue that Asia likely harbours far more Bolbitius diversity than is currently recognised, and that future studies should pair extensive fieldwork in under-sampled regions with phylogenomic approaches. For a genus of mushrooms that lives fast, dies by self-digestion and hides in the leaf litter of remote forests, the message of this study is clear: look closely, sequence everything, and expect more surprises.

Subject of Research: Taxonomy and molecular phylogeny of the mushroom genus Bolbitius in northeast China

Article Title: Two new species and one new record of Bolbitius ( Bolbitiaceae , Agaricales ) from northeast China

Article References: Cheng, H., & Bau, T. (2026). Two new species and one new record of Bolbitius (Bolbitiaceae, Agaricales) from northeast China. MycoKeys, 140, 299-316. https://doi.org/10.3897/mycokeys.140.203173

Image Credits: AI Generated

DOI: 10.3897/mycokeys.140.203173

Keywords: Bolbitius, mycology, new species, northeast China, molecular phylogenetics, ITS, taxonomía, fungi, Bolbitiaceae, biodiversity, Agaricales, systematics