Acaulospora colossica sp. nov. from an old field in North Carolina and morphological comparisons with similar species, A. laevis and A. koskei

Abstract

A new arbuscular mycorrhizal fungal species, Acaulospora colossica, (Glomales, Acaulosporaceae) is described, and its distribution and seasonality discussed. Spores of A. colossica develop from saccules that empty their contents in the developing spores. Spore wall structure consists of 3 layers, all originating from the subtending hyphae. The two inner layers are laminated. The outermost spore wall layer is typically sloughed off before the spores mature. Two inner walls arise sequentially. Both inner walls are comprised of two layers. The outer layer of the innermost wall is beaded. Acaulospora colossica is described from a population in Durham, North Carolina. Its name refers to the relatively large size of the spores. Finally, the morphology of the new species A. colossica is compared and contrasted to two closely related species A. laevis and A. koskei.