Seven species of bioluminescent fungi are recorded from the cloud forests in Mexico. Six represent new species belonging to the genus Mycena, whereas Mycena globulispora is a new distribution record for the country. Descriptions, illustrations, photographs, and an identification key to bioluminescent fungi species from Mexico are provided. Sequences of nuc rDNA internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) region were generated for barcoding purposes and comparisons with similar species.

The nuclear ribosomal internal transcribed spacer (nrITS) region has been widely used in fungal diversity studies. Environmental metabarcoding has increased the importance of the fungal DNA barcode in documenting fungal diversity and distribution. The DNA barcode gap is seen as the difference between intra- and inter-specific pairwise distances in a DNA barcode. The current understanding of the barcode gap in macrofungi is limited, inhibiting the development of best practices in applying the nrITS region toward research on fungal diversity. This study examined the barcode gap using 5146 sequences representing 717 species of macrofungi from eleven genera, eight orders and two phyla in datasets assembled by taxonomic experts. Intra- and inter-specific pairwise distances were measured from sequence and phylogenetic data. The results demonstrate that barcode gaps are influenced by differences in intra- and inter-specific variance in pairwise distances. In terms of DNA barcode behavior, variance is greater in the ITS1 than ITS2, and variance is greater in both relative to the combined nrITS region. Due to the difference in variance, the barcode gaps in the ITS2 region are greater than in the ITS1. Additionally, the taxonomic approach of “splitting” taxa into numerous taxonomic units produces greater barcode gaps when compared to “lumping”. The results show variability in the barcode gaps between fungal taxa, demonstrating a need to understand the accuracy of DNA barcoding in quantifying species richness. For taxonomic studies, variability in nrITS sequence data supports the application of multiple molecular markers to corroborate the taxonomic and systematic delineation of species.

During nocturnal field expeditions in the Brazilian Atlantic Rainforest, an unexpected bioluminescent fungus with reduced form was found. Based on morphological data, the taxon was first identified as belonging to the cyphelloid genus Maireina, but in our phylogenetic analyses, Maireina was recovered and confirmed as a paraphyletic group related to genera Merismodes and Cyphellopsis. Maireina filipendula, Ma. monacha, and Ma. subsphaerospora are herein transferred to Merismodes. Based upon morphological and molecular characters, the bioluminescent cyphelloid taxon is described as the new genus Eoscyphella, characterized by a vasiform to urceolate basidiomata, subglobose to broadly ellipsoid basidiospores, being pigmented, weakly to densely encrusted external hyphae, regularly bi-spored basidia, unclamped hyphae, and an absence of both conspicuous long external hairs and hymenial cystidia. Phylogenetic analyses based on ITS rDNA and LSU rDNA support the proposal of the new genus and confirm its position in Cyphellopsidaceae. Eoscyphella luciurceolata represents a new lineage of bioluminescent basidiomycetes with reduced forms.

All known bioluminescent fungi are basidiomycetes belonging to the Agaricales. They emit 520–530 nm wavelength light 24 h per day in a circadian rhythm. The number of known bioluminescent fungi has more than doubled in the past 15 years from 64 to 132 species. We currently recognize five distinct lineages of bioluminescent Agaricales belonging to the Omphalotaceae (18 species), Physalacriaceae (14), Mycenaceae (96), Lucentipes lineage (3), and Cyphellopsidaceae (1). They are distributed across the globe with the highest diversity occurring on woody or leafy substrates in subtropical closed canopy forests with high plant diversity. With the caveat that most regions of the world have not been extensively sampled for bioluminescent fungi, the areas with the most known species are Japan (36), South America (30), North America (27), Malesia, South Asia, and Southeast Asia (26), Europe (23), Central America (21), China (13), Africa (10), Australasia, Papua New Guinea, and New Caledonia (11), and the Pacific Islands (5). Recent studies have elucidated the biochemical and genetic pathways of fungal bioluminescence and suggest the phenomenon originated a single time early in the evolution of the Agaricales. Multiple independent evolutionary losses explain the absence of luminescence in many species found within the five lineages and in the majority of Agaricales.

A  Mycena species new to science was obtained from moist chamber cultures of trunk bark of a living American elm tree (Ulmus americana) located in the Fort Worth Botanic Garden, Tarrant County, Texas. This discovery was part of an ongoing study of corticolous myxomycetes on larger American elm trees occurring in Fort Worth nature parks. More than 15 American elm trees were sampled for trunk bark but only a single tree yielded  Mycena basidiomes. Collections of bark began in the summer of 2017 and continued until the beginning of 2020. Bark samples from the north, south and west side of the tree yielded fruit bodies of the mushroom in moist chamber culture. No fruit bodies were observed in nature nor were early formation stages on the underside of the bark. Crystals previously described in another study were present on the bark surfaces, edges, and undersides. Habit and morphological development were photographed using light microscopy applying multifocal imaging and computer stacking to increase depth of field. Basidiome development was observed and photographed from the earliest primordial beginning stage, the button stage, intermediate stage and the final emerging stalk elongation and mature cap formation stage. Mature mushroom development took from 9 to 21 days after wetting the bark in moist chamber cultures. Scanning electron microscopy was used to illustrate development of the button stage, emerging stalk and pileus stage, and the fully mature pileus, lamellae, and pseudocollarium. Morphological features and DNA sequence data confirmed that this  Mycena species was undescribed and distinct from other  Mycena taxa. Morphological features suggest placement of the novel taxon in  Mycena sect. Viscipelles, distinct from other members based on morphological characters and phylogenetic analysis.