Pygmaeomycetaceae, a new root-associated family in Mucoromycotina from the pygmy pine plains

A new genus, <i>Pygmaeomyces</i>, and two new species are described based on phylogenetic analyses and phenotypic and ecological characters. The species delimitation was based on concordance of gene genealogies. The <i>Pygmaeomyces</i> cultures were isolated from the roots of mountain laurel (<i>Kalmia latifolia</i>) and pitch pine (<i>Pinus rigida</i>) from the acidic and oligotrophic New Jersey pygmy pine plains; however, they likely have a broader distribution because their internal transcribed spacer (ITS) sequences have high similarity to a number of environmental sequences from multiple independent studies. Based on the phylogeny and phenotypic characters, a new family, Pygmaeomycetaceae, is proposed to accommodate this new lineage in Mucoromycotina. Pygmaeomycetaceae corresponds to Clade GS23, which was identified based on a sequence-only soil fungal survey and was believed to be a distinct new class. Compared with the culture-based methods, we observed that sequence-only analyses tend to overestimate the taxonomic level. Results from this work will facilitate ecological and evolutionary studies on root-associated fungi.