After morphological scrutiny and DNA-based phylogenetic analysis, Isolate 527 is now Durabilispora carpatica, the founding species of a new genus in the family Rhizoglomeraceae, while Isolate 530 has been named Dominikia tatrensis, a new species in the family Dominikiaceae. Both belong to the order Glomerales within the phylum Glomeromycota, the arbuscular mycorrhizal fungi. Roughly 370 species of this phylum have been described so far, but estimates built from environmental DNA sequences suggest that this figure represents anywhere from 0.04 to 36 percent of the species actually existing worldwide.

Those same environmental surveys indicate that many of the undescribed fungi are close relatives of Dominikia, making the discovery of D. tatrensis particularly timely. The story began with thirty-two trap cultures prepared from soils collected in the Tatra Mountains of southern Poland and northern Slovakia, part of the Carpathians, one of Europe’s most important mountain massifs. Among the fungal specimens extracted from these cultures, two stood out for their unusual morphology.

Isolate 527 came from a windfall open area in the lower part of the Dolina Miętusia Valley at 938 meters above sea level, sampled in July 2023, while Isolate 530 was collected in May 2023 from the Polana Upłaz meadow at 1298 meters, at the edge of a spruce forest. The two sites differ markedly in soil chemistry: the Isolate 527 soil was more acidic, with a pH of 5.17, lower carbon and nitrogen content, and far less calcium than the near-neutral soil of the Isolate 530 site. Numerous attempts to grow both fungi in single-species cultures failed, so the descriptions rest on specimens from trap pot cultures, in which Plantago lanceolata served as the host plant under controlled conditions of 22 degrees Celsius and a 12-hour light regime.

Under the microscope, both fungi produce their spores in compact, hypogeous fruiting bodies called glomerocarps, which lack a peridium, the protective outer covering seen in some relatives. Durabilispora carpatica forms globose to subglobose glomerocarps measuring 394 to 446 micrometers in diameter, sometimes fused to one another, each containing tens to roughly a hundred randomly distributed orange to yellowish brown spores of 35 to 56 micrometers. Dominikia tatrensis builds smaller glomerocarps, 154 to 280 micrometers across, holding five to twelve greyish yellow spores arranged radially around a centrally located swollen cell from which their subtending hyphae branch.

In both species, the spore wall consists of four layers continuous with the wall of the subtending hypha, and the fine details of these layers, their thicknesses, colors, and reactions to Melzer’s reagent, provide the diagnostic characters that separate the new taxa from their closest relatives. The researchers therefore reconstructed phylogenies from two independent sources of molecular data: the 45S nuclear ribosomal DNA region, spanning the 18S, ITS1, 5.8S, ITS2, and 28S segments, and the rpb1 gene, which encodes the largest subunit of RNA polymerase II. This dual approach matters because all rDNA loci used in studies of Glomeromycota are polymorphic and can lead to erroneous interpretations of closely related species, a risk that is greatly reduced when inferences are additionally based on protein-coding gene sequences, which show much lower variability.

The rpb1 gene has become a powerful tool in Glomeromycota systematics because it is single-copy, avoiding problems with paralogous sequences, and contains several highly variable regions useful for species discrimination. Sequences were amplified with primers designed by Stockinger and colleagues, cloned, sequenced, and analyzed through Bayesian inference and maximum likelihood methods, with alignments partitioned by gene region and substitution models applied to each partition separately. The results were unambiguous.

In trees combining 45S and rpb1 sequences, Isolate 527 occupied an autonomous clade in a basal position to the clade containing the seventeen known species of Rhizoglomus, with full statistical support from both analytical approaches. Its 45S sequences diverged from those of its closest relatives, Rhizoglomus invermaium and R. melanum, by 12.4 to 13.2 percent, clearly exceeding the 10 percent threshold that delimits other generic clades in Glomerales. Isolate 530, by contrast, nested within Dominikia as a sister clade to Dominikia aurea, with full Bayesian and strong maximum likelihood support.

The two species differ by 2.4 to 4.2 percent in their 45S sequences and by more than 1.1 percent in key regions of rpb1, exceeding accepted thresholds of conspecificity. Notably, the environmental sequence database EUKARYOME had already flagged a cluster of unassigned sequences, called gen21, that turned out to correspond to Durabilispora, corroborating the new genus independently. Those environmental sequences also hint at a wider, if rare, distribution. Among many sequences with more than 96 percent identity retrieved by BLAST searches, only four clustered reliably with Durabilispora carpatica, originating from forest soils in Estonia, Mexico, and Qatar. For Dominikia tatrensis, five environmental sequences clustered with the new species, coming from Estonian shrubland and forest soils, roots of Brachypodium pinnatum in a Czech meadow, and soil from the Qinghai-Tibet Plateau in China. The authors conclude that both fungi are probably widespread across the globe but occur rarely.

The morphological comparisons reinforce the molecular case in detail. Durabilispora carpatica differs from R. invermaium in possessing a four-layered rather than two-layered spore wall, a thicker and colored outer layer, wider subtending hyphae, and a pore that is usually open rather than closed by a septum. Against R. melanum, the new species stands out by its permanent outer wall layer, which remains intact even in old spores, whereas in R. melanum this layer is typically sloughed off entirely. Dominikia tatrensis differs from its closest relative D. aurea in the radial arrangement of its spores around a swollen cell, the presence of wall layers absent in D. aurea, and a more durable outer wall layer, and from the morphologically similar but non-sequenced Glomus fuegianum in lacking both a peridium and the strands of compact parallel hyphae that separate spore groups within G. fuegianum glomerocarps. The only other Glomeromycota species known to form fused glomerocarps, Sclerocystis coremioides, arranges its spores radially around a central plexus of hyphae and covers its fruiting bodies with a peridium, unlike the randomly arranged, naked glomerocarps of Durabilispora. Beyond the descriptions themselves, the study carries a methodological warning.

The researchers found that relying on sequences of only exons 4 and 5 of the rpb1 gene, a shortcut proposed in earlier work, was insufficient to separate D. tatrensis from D. aurea, and likewise failed to distinguish certain other closely related species pairs that differ clearly in full-gene phylogeny and morphology. In contrast, using the complete rpb1 sequence, spanning exons 1 through 5 plus all four introns, cleanly separated all tested species. Because all ribosomal DNA loci used in AMF identification are polymorphic and can mislead interpretations of closely related species, the authors recommend that taxonomic decisions rest on full rpb1 sequences combined with 45S data, provided the resulting phylogenies do not conflict. The discovery also closes a historical loop: mycological surveys of the Tatras stretching back to the 1960s documented the common occurrence of arbuscular mycorrhiza in the region’s plant communities, but the fungi responsible could not be identified because the wet sieving and decanting technique used to collect their spores was not yet known, and subsequent work had recorded 26 AMF species in the region before this study. With holotypes deposited at ETH Zurich, isotypes in Szczecin, Poland, and sequences publicly available in GenBank, the Tatra Mountains have yielded two more pieces of one of biology’s least charted inventories.

Subject of Research: Taxonomy and phylogeny of arbuscular mycorrhizal fungi in the order Glomerales

Article Title: A new genus ( Durabilispora ) and two new species ( D. carpatica , Dominikia tatrensis ) in Glomerales ( Glomeromycota )

Article References: Błaszkowski, J., Milczarski, P., Malinowski, R., Niezgoda, P., Goto, B. T., Ronikier, A., Stanek, M., Janik, P., & Zubek, S. (2026). A new genus (Durabilispora) and two new species (D. carpatica, Dominikia tatrensis) in Glomerales (Glomeromycota). MycoKeys, 134, 313-340. https://doi.org/10.3897/mycokeys.134.187344

Image Credits: AI Generated

DOI: 10.3897/mycokeys.134.187344

Keywords: arbuscular mycorrhizal fungi, Glomeromycota, Glomerales, Durabilispora carpatica, Dominikia tatrensis, Tatra Mountains, taxonomy, phylogenetics, rpb1 gene, 45S rDNA, new species, fungal biodiversity