Hidden Fungal Lineages Emerge from the Yunnan–Guizhou Plateau, Rewriting Polyporales Evolution

Deep in the subtropical forests of the Yunnan–Guizhou Plateau, a team of mycologists has quietly pulled back the curtain on one of the most species-rich corners of the fungal tree of life. In a study published in IMA Fungus, researchers describe one entirely new genus and six new species of wood-decaying fungi in the order Polyporales, a group whose members are the unsung engineers of forest decomposition. The discovery, based on years of fieldwork across Yunnan Province combined with multilocus DNA sequencing and molecular clock analyses, offers a vivid reminder that even well-studied groups of organisms can still conceal entire lineages waiting to be named.

Polyporales is one of the major orders within Basidiomycota, the phylum that includes roughly 53,000 described species. Most polypores are saprotrophic wood-decay fungi that cause white or brown rot, breaking down lignin and cellulose in dead trees and driving nutrient cycling in forests from the tropics to the boreal zone. Some are edible or medicinal, others are forest pathogens, and all of them play a role in the four-part architecture of a healthy ecosystem: non-biological components, producers, consumers, and decomposers. Without fungi, dead wood would pile up and the materials locked inside it would never return to the soil.

The order has grown dramatically in recognized diversity. Kirk and colleagues reported approximately 1,800 species, 216 genera, and 13 families in Polyporales in 2008; by 2024, about 2,544 species, 285 genera, and 18 families had been recognized. Yet the higher-level relationships within the order remain notoriously difficult to resolve, partly because no single morphological feature unites all Polyporales. Members range from bracket-shaped shelf fungi to effused-resupinate crusts, with hymenophores that are poroid, lamellate, labyrinthiform, or smooth, and transitions among these forms occur repeatedly across the order.

The new study focused on two families within Polyporales: Irpicaceae and Steccherinaceae. Both are important wood-decaying fungi that cause white rot on angiosperm and gymnosperm wood, and both have undergone extensive taxonomic revision in recent years, with the familial placements of some taxa still unresolved. To untangle these relationships, the researchers reconstructed phylogenies using multilocus DNA sequence data, including the internal transcribed spacer ITS, the nuclear large subunit nLSU, the mitochondrial small subunit mtSSU, the translation elongation factor gene tef1-α, and the second subunit of RNA polymerase II rpb2. Two combined datasets were assembled: a five-gene dataset for Steccherinaceae and a two-gene ITS+nLSU dataset for Efibula and related species in Irpicaceae.

The results are striking. Three new species of Efibula, one new species of Phanericium within Irpicaceae, and one new genus, Odentinium, including two new species within Steccherinaceae, are described and illustrated. The genus Odentinium is characterized by resupinate basidiomata with an odontioid hymenial surface, a monomitic hyphal system with clamped generative hyphae, cylindrical cystidia that are strongly encrusted, and ellipsoid, smooth basidiospores. Its two species, Odentinium aurantium and Odentinium cremeum, were collected on fallen angiosperm branches at altitudes above 2,200 meters in the Yaoshan National Nature Reserve and surrounding forests, forming a distinct lineage with strong phylogenetic support within Steccherinaceae.

Morphologically, Odentinium stands apart from related genera. Mycorrhaphium differs by flabelliform pileate basidiomata with imbricate growth, a hydnoid hymenial surface, clavate basidia, and narrowly ellipsoid basidiospores. Nigroporus differs by pileate to resupinate, scrupose to glabrous, azonate to concentrically zonate, grayish-blue basidiomata, a dimitic hyphal system, and allantoid to broadly ellipsoid basidiospores. Rhomboidia can be distinguished by its stipitate basidiomata, monomitic hyphal system, and broadly ellipsoid basidiospores, while Trullella differs by polyporoid, trematoid, or fibroporioid basidiomata, a dimitic hyphal system with clamped generative hyphae, and phaseoliform to allantoid basidiospores. The new genus clusters with these related genera in the phylogenetic tree but occupies its own well-supported branch.

The three new Efibula species also reveal the genus to be more complex than previously thought. Efibula was traditionally classified in the family Phanerochaetaceae, but phylogenetic analyses now support its placement in Irpicaceae. Earlier studies determined that Efibula was not monophyletic but formed three distinct clades, one of which was described as the new genus Phanericium by Larsson and colleagues in 2025. In the present study, Efibula murina groups with E. grandinosa and E. shenghuae, Efibula yaoshanensis is recovered as sister to E. yunnanensis, and Efibula zhaotongensis forms a clade closely related to E. bubalina. The new species Phanericium bambusacearum, collected on dead bamboo, was grouped within Phanericium and was sister to P. subglobisporum, confirming that Phanericium clusters with Efibula.

Beyond naming new species, the study reached deep into evolutionary time. Using Bayesian evolutionary analysis with three fossil calibrations—Archaeomarasmius leggetti as a representative of the minimum age of Agaricales at 90 million years ago, Quatsinoporites cranhamii as a representative of the minimum age of Hymenochaetaceae at 125 million years ago, and Paleopyrenomycites devonicus as a representative of the minimum age between Basidiomycota and Ascomycota at 400 million years ago—the researchers estimated divergence times across Polyporales. The ancestors of Irpicaceae are estimated to have emerged with a mean crown age of 199.17 million years ago, followed by Steccherinaceae with a mean crown age of 142.95 million years ago, and the genus Odentinium with a mean crown age of 120.8 million years ago. These dates place the origins of both families in the Jurassic and Early Cretaceous, an era when flowering plants were just beginning their rise to dominance.

The subtropical monsoon climate and high average annual precipitation of the Yunnan–Guizhou Plateau favor the establishment of a diverse macrofungal community, and the region has proven to be a hotspot for wood-inhabiting fungi. Fresh basidiomata growing on angiosperm branches were photographed in situ from July 2019 to January 2024, dried in electric food dehydrators at 30–50 °C, and deposited in the herbarium of Southwest Forestry University in Kunming. Micromorphological data were obtained from dried specimens observed under a light microscope, with standardized sampling of basidiospores, basidia, basidioles, cystidia, and hyphal diameters. DNA was extracted from dried specimens using the EZNA HP Fungal DNA Kit, amplified across five gene regions, and sequenced, with all newly generated sequences deposited in GenBank.

The study fills knowledge gaps regarding wood-inhabiting fungi by reporting new taxa and providing detailed morphological descriptions and phylogenetic analyses, while contributing to the enrichment of fungal diversity in Asia. With the application of molecular phylogeny, more fungal species are expected to be reported from the Oriental realm, as wood-inhabiting fungi are cosmopolitan and particularly abundant in this region. Further studies should focus on relationships between hosts and wood-inhabiting fungi, and large-scale phylogenetic reconstructions of Polyporales still suffer from missing data and limited taxon sampling, which influence inferences of backbone relationships. The Yunnan–Guizhou Plateau, it seems, has much more to reveal.

Subject of Research: Discovery and evolutionary dating of one new fungal genus and six new species of wood-decaying fungi in Irpicaceae and Steccherinaceae from the Yunnan–Guizhou Plateau

Article Title: Morphological and phylogenetic analyses reveal one new genus and six new species in Irpicaceae and Steccherinaceae ( Polyporales , Basidiomycota ) from the Yunnan–Guizhou Plateau, Asia

Article References: Deng, Y., Chen, M., Wang, K., Liu, W., Chen, D., Yang, S., Li, W., Zhou, H., & Zhao, C. (2025). Morphological and phylogenetic analyses reveal one new genus and six new species in Irpicaceae and Steccherinaceae (Polyporales, Basidiomycota) from the Yunnan–Guizhou Plateau, Asia. IMA Fungus, 16, Article e172367. https://doi.org/10.3897/imafungus.16.172367

Image Credits: AI Generated

DOI: 10.3897/imafungus.16.172367

Keywords: mycology, Polyporales, fungal taxonomy, Yunnan-Guizhou Plateau, wood-decaying fungi, phylogenetics, molecular clock, new species, Morphological, phylogenetic, analyses, reveal