Uncovering Diversity within the Glomeromycota: Novel Clades, Family Distributions, and Land Use Sensitivity

Arbuscular mycorrhizal fungi (AMF, phylum Glomeromycota) are essential to plant community diversity and ecosystem functioning. However, increasing human land use represents a major threat to native AMF globally. Characterizing the loss of AMF diversity remains challenging because many taxa are undescribed, resulting in poor documentation of their biogeography and family-level disturbance sensitivity. We survey sites representing native and human-altered ecosystems across the American continents-in Alaska, Kansas, and Brazil-to shed light on these gaps. Using a recently developed pipeline for phylogenetic placement of eDNA, we find evidence for three putative novel clades within the Glomeromycota, sister to <i>Entrophosporaceae</i>, <i>Glomeraceae</i>, and <i>Archaeosporaceae</i>, with evidence for geographic structuring. We further find that taxa in the <i>Diversisporaceae</i>, <i>Glomeraceae</i>, and <i>Entrophosporaceae</i> relatively high families are overrepresented and more diverse in temperate samples. By contrast, the diversity of taxa that cannot be placed into a family is higher in tropical samples, suggesting that tropical sites harbor relatively high undescribed AMF diversity. Moreover, we find evidence that <i>Entrophosporaceae</i> is more tolerant, while <i>Glomeraceae</i> is more sensitive to disturbance. These results underscore the vast undescribed diversity of AMF while highlighting a way forward to systematically improve our understanding of AMF biogeography and response to human disturbance.