Fungal Family Tree Rewritten: New Genus and Nine Species Reclassified Among Sporidesmium-Like Molds

A sweeping phylogenetic and morphological reassessment of Sporidesmium-related fungi has resolved one of mycology’s more tangled taxonomic puzzles, splitting a long-ambiguous group of wood-inhabiting molds into seven distinct evolutionary lineages. The study, published in MycoKeys, introduces a new genus, Lignosporidesmium, a new species, Xenosporidesmium lignicola, and transfers nine species into more appropriate genera, all grounded in a five-gene phylogenetic framework combined with detailed microscopic examination.

Sporidesmium sensu lato has long served as a catch-all for hyphomycetous fungi sharing a recognizable morphology: solitary or gregarious conidiophores bearing mono- to polyblastic conidiogenous cells that produce pale brown to dark brown conidia, typically cylindrical, fusiform, obclavate, or rostrate in shape, with hyaline apices and truncate bases, with or without a sheath. As molecular sequencing became routine, many taxa once lumped into this broad concept were moved into natural classifications, including Distoseptispora, Ellisembia, Lomaantha, Xenosporidesmium, Pleotrichocladium, and Neopseudocercospora. Yet several lineages remained poorly resolved, hampered by incomplete type material, limited sampling, or the absence of molecular data altogether.

To untangle these relationships, the researchers assembled a concatenated dataset of LSU, ITS, rpb2, SSU, and tef1-α sequences totaling 4,244 characters, including gaps, from 195 ingroup strains primarily representing members of the class Sordariomycetes. Maximum likelihood analysis conducted with RAxML resolved Sporidesmium sensu lato into seven well-supported clades, labeled A through G. Bayesian inference with MrBayes produced similar overall topologies, with bootstrap support values above 65 percent and posterior probabilities above 0.97 reported at the nodes. Chlorociboria aeruginosa and Dermea acerina served as outgroup taxa, and the best RAxML tree had a final likelihood of −125613.051159.

The clades each carry distinct biological identities. Clade A, strongly supported at the apex of the tree, comprises 14 species plus an unnamed Sporidesmium strain and is characterized by continuously proliferating conidiogenous cells and mature conidia that are brown to black and pyriform or lageniform. The authors propose that this clade represents Sporidesmium sensu stricto, although they note that the lectotype species, Sporidesmium ehrenbergii, has never been recollected and lacks molecular sequence data, leaving its precise relationship to clade A formally unresolved. Clade B contains three species of Lylea, including the newly combined Lylea lignicola, while Clade C groups Sporidesmium appendiculatum, S. chiangmaiense, Ellisembia minigelatinosa, and two unnamed strains into a lineage sister to clade B. Clade D holds seven species previously treated as Ellisembia sensu stricto and sits as a strongly supported sister to clades A, B, and C.

Clade E corresponds to Xenosporidesmium as circumscribed by Liu and colleagues in 2025, a genus distinguished by distoseptate conidia paler toward the apex and enclosed by a mucilaginous sheath or bearing an apical appendage, with basal conidial cells concolorous with the remaining cells. Clade F consists of four strains of the newly erected Lignosporidesmium tropicale, which cluster with Bullimyces communis and Ceratolenta caudata of the order Ceratolentales, though the authors caution that this relationship lacks robust statistical support; they place the new genus in Diaporthomycetidae genera incertae sedis. Clade G includes two genetically divergent species, Sporidesmium macrurum and S. gyrinomorphum, nested unexpectedly within Xylariomycetidae, and the authors defer formal taxonomic revisions for this lineage pending further study.

The new genus Lignosporidesmium, with the type species L. tropicale (formerly Sporidesmium tropicale), is defined by a combination of euseptate conidia, non-proliferating conidiogenous cells, and pale brown to brown, obclavate, rostrate conidia that are verrucose and lack sheaths. This separates it from clades B, C, and D, whose members bear distoseptate conidia, and from clade A, whose species show proliferating conidiogenous cells and darker, pyriform to lageniform mature conidia. Sporidesmium tropicale itself is a widespread tropical species, reported from diverse plant substrates including Hainan, Guangdong, and Guangxi in China, and its strains from different regions and habitats consistently share key morphological traits, indicating a lineage of high evolutionary stability.

The newly described species, Xenosporidesmium lignicola, was collected during surveys of lignicolous freshwater fungi on submerged decaying wood in the Dulongjiang River, Yunnan Province, China, at an elevation of 1,702 meters. Its holotype, HKAS 135961, was deposited in the herbarium of Cryptogams at the Kunming Institute of Botany, with the ex-type culture preserved as CGMCC 3.27664. Morphologically, the species produces conidiophores measuring (26.5–)34–49(–60) × 3.2–4.5 micrometers, monoblastic integrated terminal conidiogenous cells, and broadly fusiform to obclavate conidia of (27–)32–40(–43) × 8–10(–12) micrometers that are 6–8-distoseptate, guttulate, and bear a thin, subglobose mucilaginous sheath 7–11 micrometers in diameter around the apical one to two cells. In multigene phylogenetic analyses, X. lignicola formed a well-supported clade with X. aquaticivaginatum, X. bostenicum, X. guttulatum, X. nujiangense, X. olivaceoconidium, and X. yangzonghaiense, yet resolved as a genetically distinct lineage within it.

Beyond the new species, the study reclassified nine taxa through new combinations. Sporidesmium lignicola was transferred to Lylea based on its clustered conidiophores and catenate conidia, features that depart sharply from the traditional Sporidesmium concept; the authors note that BLASTn comparison of a newly generated ITS sequence from the ex-paratype DLUCC 1376 showed its closest match to be Lylea tetracoila at 98 percent identity (505 of 513 base pairs identical, with one gap), but given limited molecular evidence and apparent geographic separation, they tentatively treat it as a distinct species. Eight additional species previously described in Sporidesmium were moved into Xenosporidesmium, including X. bostenicum, X. dianchiense, X. distoseptatum, X. hongheense, X. lacustris, X. mucilaginosum, X. yangzonghaiense, and X. yilonghuense. A newly collected strain of X. yilonghuense from the Dulongjiang River, a lotic habitat unlike the lake habitats of prior records, clustered stably with previously reported strains and showed nucleotide differences of 13 base pairs in ITS, 9 in LSU, and 2 in tef1-α from the type material, extending the known distribution of the species.

The study also confronts the practical limits of integrative taxonomy. Species described in earlier publications without sequence data, particularly those with poorly preserved or incomplete specimens, remain extremely difficult to place reliably. Original descriptions are sometimes brief or lack detailed illustrations, and type specimens are often dispersed across multiple countries, institutions, or private herbaria, creating logistical, legal, and financial obstacles for researchers seeking to examine them. The authors emphasize that revising Sporidesmium-related taxa frequently requires morphological re-examination, field recollection of fresh material, and generation of new molecular data in combination, and they highlight the need for re-collection and fresh sequencing for lineages whose positions remain uncertain, including clade C and the Xylariomycetidae-nested clade G.

What emerges is a portrait of a morphologically diverse group whose classification can only stabilize through integrative approaches that marry microscopy with multigene phylogenetics. The seven-clade framework now provides a scaffold: Sporidesmiaceae housing clades A, B, and C; Xenosporidesmiaceae housing clade D; and Lignosporidesmium standing apart as an isolated lineage of still-uncertain familial placement. For freshwater fungal diversity in Yunnan Province, one of the most intensively surveyed hotspots for lignicolous freshwater fungi owing to its complex topography and abundant freshwater resources, the study adds both a new species and a clearer evolutionary context, while underscoring how much of fungal diversity still awaits molecular characterization.

Subject of Research: Multigene phylogenetic and morphological reassessment of Sporidesmium-related freshwater fungi, describing a new genus and new species

Article Title: Phylogenetic and morphological reassessment of Sporidesmium -related taxa reveals Lignosporidesmium gen. nov. and Xenosporidesmium lignicola sp. nov.

Article References: Shen, H.-W., Hyde, K. D., Wang, Y., Yang, L., Su, X.-J., Li, Y.-X., & Luo, Z.-L. (2026). Phylogenetic and morphological reassessment of Sporidesmium-related taxa reveals Lignosporidesmium gen. nov. and Xenosporidesmium lignicola sp. nov.. MycoKeys, 142, 293-316. https://doi.org/10.3897/mycokeys.142.216747

Image Credits: AI Generated

DOI: 10.3897/mycokeys.142.216747

Keywords: Sporidesmium, Xenosporidesmium, Lignosporidesmium, fungal taxonomy, multigene phylogeny, freshwater fungi, hyphomycetes, Sordariomycetes, new species, Yunnan Province, mycology, systematics