Dimorphic spore production in the genus Acaulospora

• Both glomoid and acaulosporoid spores were found in four Acaulospora species.
• Molecular analysis confirmed that cultures of A. spinosa contained a single species.
• The production of glomoid spores cannot be used as a taxonomic character.

Species of the genus Acaulospora are partly characterized by the production of ‘acaulosporoid’ spores. The simultaneous formation of glomoid and acaulosporoid spores by some species in the Glomeromycota has been used as a basis for taxonomic classification. We report the presence of both glomoid and acaulosporoid spores in four Acaulospora species. Analysis of the 18S rRNA gene confirmed that only A. spinosa was present in a pot culture that produced two morphs. The functional significance of dimorphic spore production is unknown but the production of blastic spores is not a characteristic that can have any significance as a taxonomic character.