Three new wood-decaying fungal species discovered in Southwest China’s forests

Deep in the subtropical forests of Yunnan Province, Southwest China, researchers have identified three previously unknown species of wood-inhabiting fungi, quietly expanding our picture of one of the planet’s most important groups of decomposers. The new species, named Phanerochaete albomarginata, Phanerochaete nigella, and Rhizochaete membranacea, belong to the family Phanerochaetaceae within the order Polyporales, a lineage of Basidiomycota famous for its ability to dismantle dead wood. The discovery, published in MycoKeys, was based on a combination of careful microscopic examination and DNA-based phylogenetic analysis, and it enriches the known fungal diversity of subtropical Asia while clarifying evolutionary relationships within the family.

Wood-inhabiting fungi are the unsung recyclers of forest ecosystems. They colonize living trees, dead standing trunks, fallen branches, stumps, and even manufactured wood products, secreting enzymes that break down cellulose, hemicellulose, and lignin into simpler substances. This decomposition process returns carbon locked in woody tissue back into the forest’s nutrient cycles, making these fungi essential players in forest carbon cycling. Functionally, they are divided into white-rot taxa, which can degrade all wood components including lignin, and brown-rot taxa, which strip away cellulose while modifying lignin. All three newly described species cause white rot, a decay type with significant implications for how carbon moves through subtropical forests.

The family Phanerochaetaceae is a major group of wood-decaying fungi characterized by relatively simple fruiting bodies, known technically as basidiomata, and fewer diagnostic morphological features than those found in polypores or mushrooms. This simplicity has long made the family a taxonomic puzzle. Twenty-nine genera are currently placed in Phanerochaetaceae, including the large and morphologically diverse genus Phanerochaete, which is typified by P. alnea and distributed from boreal to tropical forests worldwide. Phanerochaete species produce resupinate, membranaceous basidiomata that lie flat against the wood surface, with a monomitic hyphal system, generative hyphae mostly with simple septa, and thin-walled, non-amyloid basidiospores. Based on Index Fungorum, 228 species epithets of Phanerochaete are registered, a testament to the genus’s remarkable diversity.

The genus Rhizochaete, by contrast, is a smaller and more distinctive lineage, introduced in 2004 and typified by R. brunnea. Rhizochaete species produce hyphal cords, root-like strands of fungal tissue that extend outward from the fruiting body, and their basidiomata are loosely adnate and fragile, with hymenial surfaces that can be yellow, orange, brown, olivaceous, or violaceous, often turning red to violet in potassium hydroxide solution. Twenty-eight records of Rhizochaete are registered in Index Fungorum, and the genus has been steadily enriched by new species descriptions from around the world, including several from China in recent years.

The three new species were collected from broad-leaved forests in Puer and Zhaotong, Yunnan Province, growing on fallen angiosperm branches. The specimens were photographed in the field using focus-stacking software, dried at 40 degrees Celsius, and deposited in the herbarium of Southwest Forestry University in Kunming. Phanerochaete albomarginata was collected in Weiyuanjiang Provincial Nature Reserve at an elevation of 1,005 meters, P. nigella in Mangyu Grand Canyon at 1,200 meters, and R. membranacea in Yaoshan National Nature Reserve at a striking 3,251 meters. Each species was examined under a light microscope at 1,000x magnification, with sections mounted in 5% potassium hydroxide and 2% Phloxine B, and additional tests using Cotton Blue and Melzer’s reagent to check for changes in spore measurements.

Morphologically, each new species carries a distinct signature. Phanerochaete albomarginata, whose name refers to the white margin of the type specimens, produces annual, resupinate, membranaceous basidiomata up to 4 centimeters long with a smooth, cream hymenial surface. It has a monomitic hyphal system with simple septa, abundant tapering cystidia that are thin-walled and occasionally contain oil drops, and ellipsoid basidiospores measuring 7.1 to 9.2 by 4.1 to 4.9 micrometers. Phanerochaete nigella, named for the black hymenial surface of the type specimens, produces coriaceous, leather-like basidiomata up to 8 centimeters long with a tuberculate, gray to black hymenial surface, tubular cystidia, and smaller ellipsoid basidiospores measuring 4.7 to 5.7 by 2.5 to 3.2 micrometers.

Rhizochaete membranacea, named for its membranaceous basidiomata, produces annual, resupinate fruiting bodies up to 10 centimeters long with a smooth, cracked hymenial surface that is slightly buff when fresh and slightly brown upon drying. Its generative hyphae are encrusted with crystals, and it produces numerous lamprocystidia, specialized defensive cells encrusted with heavy crystals, measuring 24 to 45 by 8 to 11 micrometers. The basidiospores are ellipsoid, measuring 4 to 5.5 by 2.7 to 3.1 micrometers. The researchers suggest that the abundant lamprocystidia may serve a defensive function against fungivorous microarthropods, a trait previously documented in other Rhizochaete species, adding an intriguing ecological dimension to the species’ morphology.

To resolve the evolutionary relationships of the three new species, the team extracted genomic DNA using a CTAB-based method and amplified two molecular markers: the internal transcribed spacer (ITS) region and the nuclear large subunit ribosomal RNA (nLSU) gene. The combined ITS plus nLSU sequences were aligned with MAFFT and analyzed using both Maximum likelihood and Bayesian inference. The resulting phylograms placed P. albomarginata and P. nigella firmly within the Phanerochaete clade, while R. membranacea clustered with the Rhizochaete lineage. Phanerochaete albomarginata formed a well-supported sister relationship with P. taiwaniana and P. yingjiangensis, P. nigella was sister to P. albida, and R. membranacea formed a distinct lineage sister to R. yunnanensis with 100% bootstrap support.

The phylogenetic placement was reinforced by morphological comparisons with close relatives. Phanerochaete taiwaniana differs from P. albomarginata by its acute, crystal-encrusted cystidia and smaller basidiospores, while P. yingjiangensis lacks cystidia altogether and has narrower basidia. Phanerochaete albida differs from P. nigella by its membranous basidiomata, pale ivory to white hymenial surface, and much smaller basidiospores. Within Rhizochaete, R. yunnanensis differs from R. membranacea by its grayish-yellow to brownish-orange, loosely adnate basidiomata, longer lamprocystidia, and clavate, larger basidia. These combined lines of evidence, morphological and molecular, provided robust support for describing all three as new species.

The discovery underscores how much remains to be learned about fungal diversity in biodiversity hotspots such as Yunnan Province, a region renowned for its exceptional richness of wood-inhabiting fungi. The researchers note that taxonomic work on Phanerochaete and Rhizochaete has predominantly relied on ITS and nLSU markers alone, and they recommend that future investigations adopt multilocus datasets integrating both ribosomal and protein-coding loci to provide a more robust foundation for taxonomic and evolutionary inferences. The limited phylogenetic signal of ribosomal markers may compromise the resolution of interspecific relationships and hinder the detection of cryptic species. Future studies into the enzymatic profiles of these new taxa will deepen insight into their ecological roles in forest carbon cycling, and continued systematic surveys in undersampled tropical and subtropical regions are essential to fully document the tree of life’s fungal branch.

Subject of Research: Three new wood-inhabiting fungal species of Phanerochaetaceae (Polyporales, Basidiomycota) from Southwest China

Article Title: Three new wood-inhabiting fungal species of Phanerochaetaceae ( Polyporales , Basidiomycota ) from Southwest China

Article References: Li, Q., Wang, S., Feng, J., Shu, C., & Zhao, C. (2026). Three new wood-inhabiting fungal species of Phanerochaetaceae (Polyporales, Basidiomycota) from Southwest China. MycoKeys, 139, 183-211. https://doi.org/10.3897/mycokeys.139.199706

Image Credits: AI Generated

DOI: 10.3897/mycokeys.139.199706

Keywords: Three, wood-inhabiting, fungal, species, Phanerochaetaceae, Polyporales, Basidiomycota, Southwest, China, scientific research