Rare but widespread: A systematic revision of the truffle-forming genera <i>Destuntzia</i> and <i>Kjeldsenia</i> and the formation of a new genus, <i>Hosakaea</i>

Here we present the results of taxonomic and systematic study of the rare truffle-forming genera <i>Destuntzia</i> and <i>Kjeldsenia</i>. Truffle-forming fungi are difficult to study due to their reduced morphological features and their cryptic, hypogeous fruiting habits. The rare occurrence of <i>Destuntzia</i> and <i>Kjeldsenia</i> further compounds these difficulties due to the lack of adequate material for study. Recent forays in North Carolina and Tennessee recovered new specimens of another rarely collected fungus, <i>Octaviania purpurea</i>. Morphological and phylogenetic analysis revealed that <i>Octaviania purpurea</i> is a member of the genus <i>Destuntzia</i>, and this led us to reevaluate the taxonomic status and systematic relationships of other <i>Destuntzia</i> species. We performed a multilocus phylogenetic analysis of <i>Destuntzia</i> specimens deposited in public fungaria, including all available type material, and environmental sequences from animal scat and soil. Our analyses indicate that <i>Destuntzia</i> is a member of the family Claustulaceae within the order Phallales and is a close relative of <i>Kjeldsenia</i>. Results of our phylogenetic analysis infer that three species originally described in the genus <i>Destuntzia</i> are members of the genus <i>Kjeldsenia</i>. We propose three new combinations in <i>Kjeldsenia</i> to accommodate these species as well as a new combination in <i>Destuntzia</i> to accommodate <i>Octaviania purpurea</i>. We also describe a new genus in Claustulaceae, <i>Hosakaea</i>, to accommodate a closely affiliated species, <i>Octaviania violascens</i>. Finally, we transfer the genus <i>Destunzia</i> into the family Claustulaceae and emend the description of the family. The newly proposed combinations in <i>Destuntzia</i> and <i>Kjeldsenia</i> significantly expand the known geographic ranges of both genera. The data from metabarcode analysis of scat and soil also reveal several additional undescribed species that expand these ranges well beyond those suggested by basidiomata collections. Systematic placement of <i>Destuntzia</i> in the saprotrophic order Phallales suggests that this genus is not ectomycorrhizal, and the ecological implications of this systematic revision are discussed.