In a paper published in Mycology, a team of scientists has proposed new taxa, combinations, and reports under the Didymiaceae and Physaraceae in China, including one new genus and 11 new species.

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Source: Bo Zhang, Engineering Research Center of Chinese Ministry of Education for Edible and Medicinal Fung

The morphological characteristics of different myxomycetes growing on different substrates.

Traditionally, Diderma species are characterized by sporocarps containing irregularly shaped lime granules, which are distributed in different patterns depending on the species. Most Diderma species are sessile and have a distinctive peridium, which can be single- to triple-layered and contains globular lime granules. 

These granules may vary range from brittle and calcareous to flexible and cartilaginous. Diderma usually has a columella present, and its capillitium lacks lime nodes. In contrast, Physarum species are characterized by stipitate sporocarps, though they can occasionally be sessile. The stalk often lacks lime and the columella is absent. 

Physarum’s capillitium is connected with lime knots, and its spores are free. One key feature that distinguishes Diderma from other species in the family Physaraceae is the absence of lime knots in its non-calcareous capillitium. The taxonomic status of Diderma and Physarum has long been controversial, and the species diversity within Didymiaceae and Physaraceae also needs further exploration.

40 years of specimens

In this study, the author examined specimens recently collected and preserved at the Jilin Agricultural University herbarium (HMJAU) spanning nearly 40 years. These specimens were gathered from various regions across China, encompassing 19 provinces.

The investigation confirmed the existence of Neodiderma as an independent genus, supported by both morphological observations and phylogenetic analyses. Within the family Didymiaceae, they identified five new Neodiderma species: N. macrosporum, N. pseudobisporum, N. verrucocapillitium, N. rigidocapillitium, and N. rufum.

In the genus Physarum, they identified 6 new species (P. guangxiense, P. subviride, P. nigritum, P. biyangense, P. neoovoideum, and P. jilinense).

Phylogenetic analysis shows that Neodiderma is situated between the genera Physarum and Diderma, sharing characteristics with both. Through comprehensive analysis, integrating morphological observations and phylogenetic insights, it was suggested that the genus Neodiderma represents a transitional group between Didymiaceae and Physaraceae. These findings provide valuable insights into the internal phylogenetic relationship between Didymiaceae and Physaraceae.

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