Verrucosporaceae is a family of saprotrophic fungi characterized by what mycologists call lepiotoid features: pale caps often adorned with brightly colored scales, free white to cream gills, a central stem with a distinct ring or annular zone, and smooth or ornamented basidiospores lacking a germ pore. These fungi play a vital role in litter decomposition and nutrient cycling within forest ecosystems. Yet their taxonomic history has been anything but stable. The family was originally proposed by Jülich in 1982 with Verrucospora as the type genus, a concept rarely adopted until Kalichman and colleagues formally resurrected and redefined it in 2020, subsuming the lepiotoid fungi under this name and encompassing nine genera including Chamaemyces, Cystolepiota, Echinoderma, Lepiota, Melanophyllum, Neosecotium, Pulverolepiota, Smithiomyces, and Verrucospora.

The core problem has always been Lepiota itself. Introduced under the genus Agaricus by Persoon and elevated to generic rank by Gray in 1821, the genus has been continuously revised by generations of mycologists. Kühner established 14 sections within Lepiota in 1936 based on micromorphological features such as the scale structures on the cap and stem and the size and shape of basidiospores, laying the foundation for modern infrageneric classification. Singer later segregated several independent genera, including Smithiomyces in 1944 for taxa with a smooth pileus and an extremely thin veil, and Cystolepiota in 1951 based on a pileus covering composed of sphaerocysts and non-dextrinoid basidiospores. Despite these efforts, a stable consensus on morphology-based generic delimitations was never achieved, leading Vellinga and Huijser to tentatively reduce Pulverolepiota to sectional rank within Cystolepiota in 1998.

The advent of molecular phylogenetics provided the tool needed to cut through this confusion. Johnson and Vilgalys first demonstrated in 1998 that several morphology-defined genera were not monophyletic. Vellinga showed in 2003 that Lepiota sect. Ovisporae was polyphyletic, whereas Cystolepiota, Lepiota sect. Echinatae, Melanophyllum, and Pulverolepiota formed a single monophyletic clade. Subsequent studies with broader taxon sampling consistently corroborated the non-monophyletic nature of these traditional sections. Yet the species diversity within this family, particularly in ecologically diverse regions like China, remained largely under-explored, leaving the full picture incomplete.

To address this gap, the research team extracted total genomic DNA from fresh or dried specimens and amplified four loci: the nuclear ribosomal internal transcribed spacer (nrITS), the nuclear ribosomal large subunit (nrLSU), the RNA polymerase II second largest subunit (rpb2), and the translation elongation factor 1-alpha (tef1-α). The final dataset consisted of 467 nrITS, 167 nrLSU, 100 rpb2, and 85 tef1-α sequences, among which 353 were newly generated in this study. Sequences were aligned using MAFFT, optimized in MEGA, and unreliable regions removed using trimAl, yielding a combined alignment of 2731 base pairs. Phylogenetic reconstructions were performed using Maximum Likelihood with IQ-TREE and Bayesian Inference with MrBayes, running two independent analyses for 60 million generations. The resulting topologies from both methods were largely congruent, confirming that the genera Lepiota, Smithiomyces, Echinoderma, Cystolepiota s.l., and Pulverolepiota were all resolved as monophyletic groups.

Within Lepiota, the phylogenetic reconstruction identified 11 major clades, seven of which correspond to formally defined sections: L. sect. Stenosporae, L. sect. Helveolae, L. sect. Cristatae, L. sect. Lilaceae, L. sect. Fuscovinaceae, L. sect. Lepiota, and L. sect. Eriophorae. The remaining four represent currently unplaced lineages. A novel subsection, Lepiota sect. Eriophorae subsect. Pseudocystolepiotae, is proposed to accommodate an evolutionary transitional lineage between Cystolepiota and Lepiota sect. Eriophorae. This subsection comprises three species: L. boertmannii, which retains the typical three-layered pileus covering of core Eriophorae, and L. icterina and the newly described L. fugaciosquamosa, which possess powdery squamules and a pileus covering restricted to only two cell layers. The inclusion of these taxa highlights the highly transitional nature of this clade, which acts as a morphological and evolutionary bridge between Cystolepiota s.l. and the core Lepiota sect. Eriophorae.

Among the 17 species new to science, several illustrate the remarkable morphological diversity within this family. Cystolepiota mastoidea, described from Liaoning and Jilin Provinces, is distinguished by its discoloring basidiomata and distinctive clavate cheilocystidia with a capitate apex, features that separate it from closely related species like C. changbaishanensis. Lepiota cristatosimilis, known only from Jilin Province, exhibits strong macroscopic resemblance to the L. cristata complex but is readily distinguished by its smaller basidiomata and distinctly congophilous, rectangular, nodulose basidiospores. Lepiota rostratospora produces strikingly elongated penguin-shaped basidiospores measuring up to 16.1 micrometers in length, a feature reflected in its name derived from the Latin rostratus, meaning beaked. Lepiota flavoviridis displays a remarkable grayish yellow to grayish green coloration and stains the fingers upon handling, while Lepiota basozonata features distinctive coffee brown squamules and concentric girdles on the lower stipe.

Beyond the new species, the study also introduces three new combinations and reinstates Lepiota squamulosa, which had been transferred to Cystolepiota in 2017 but is now shown to nest securely within Lepiota sect. Eriophorae. Two species previously placed in Lepiota are formally transferred to Leucocoprinus as new combinations. The research also provides supplementary observations on the Melanophyllum haematospermum complex, revealing that this traditionally cosmopolitan species is actually a cryptic species complex comprising several distinct lineages, with East Asian collections differing from European core taxa in basidiospore dimensions and the presence or absence of cheilocystidia.

One of the most significant micromorphological findings concerns the structural homology between pileus and stipe coverings. The researchers examined the cap and stem scale microstructures of Lepiota sect. Eriophorae, Echinoderma, Cystolepiota, and Melanophyllum, recognizing two main types of pileus surface squamules: a three-layered structure with apical globose chains, exemplified by Echinoderma petaloides and Lepiota verruculosa, and a simpler two-layered pileus covering observed in certain Lepiota species, Cystolepiota, and Melanophyllum. Critically, the stipe covering structures mirror these pileus coverings in layer architecture, cellular shape, and pigmentation. This correlation extends to lineages exhibiting covering simplification: in Subclade D of L. sect. Stenosporae, although the pileus retains macroscopically small squamules, its covering is microscopically reduced to a cutis, and the stipe covering directly mirrors this structural simplification. These observations reinforce the reliability of pileus covering microstructure as a criterion for infrageneric delimitation, confirming earlier findings that this feature exhibits high evolutionary conservatism.

The study expands the current understanding of cryptic diversity within Verrucosporaceae in China and provides useful morphological and phylogenetic data for future evolutionary studies on lepiotaceous fungi. By integrating multi-locus molecular data with detailed micromorphological analyses, the researchers have contributed to a more natural classification and a clearer understanding of the evolutionary boundaries among these historically contentious groups. As specimen sampling continues across China and beyond, the framework established here will serve as the foundation for documenting the full species richness of this remarkable fungal lineage, one that has been hiding in plain sight beneath the leaf litter{

Subject of Research: Mycology, Phylogenetics, Taxonomy

Article Title: Phylogeny of Verrucosporaceae ( Basidiomycota , Agaricales ): taxonomic novelties in Cystolepiota and Lepiota from China

Article References: Phylogeny of Verrucosporaceae ( Basidiomycota , Agaricales ): taxonomic novelties in Cystolepiota and Lepiota from China. (n.d.). https://doi.org/10.3897/imafungus.17.207486

Image Credits: AI Generated

DOI: 10.3897/imafungus.17.207486

Keywords: mycology, phylogenetics, taxonomy, fungi, biodiversity, China, Lepiota, Cystolepiota, Verrucosporaceae, Phylogeny, Basidiomycota, Agaricales