Archaeospora europaea, a new fungus in the Archaeosporomycetes (Glomeromycota), was isolated from multiple agricultural production systems in France, Germany, Italy and Switzerland. It was cultivated in trap and monosporic single species cultures on Trifolium pratense, Lolium perenne, Plantago lanceolata and Hieracium pilosella. The fungus is bimorphic, but in our cultures it formed predominantly bi-walled acaulo-archaeosporoid spores, globose to subglobose, rarely oblong, ovoid or irregular, and (50)65–87 × (48)64–85 μm in diameter, while the hyaline glomoid spores, 25–38(55) × 20–31 μm, were rarely observed. By morphology, A. europaea can be differentiated from all other Archaeosporomycetes species by the small, bi-walled acaulo-archaeosporoid spores formed laterally on the neck of sporiferous saccules without pedicel formation and by a wrinkled second spore wall layer in PVLG-based mountants that stains yellow to pinkish yellow in Melzer’s reagent. The glomoid spores resemble glomoid spores of any other Archaeosporaceae species and might, to our opinion, hardly be used for species identification. Phylogenetically, A. europaea forms a separate clade closest to Archaeospora trappei. The isolation sites of A. europaea were various agricultural production systems and soils with variable nutritional and soil cultivation levels. Time to spore formation of the new species was short with only 3–6 months, as observed in several greenhouse cultures.
