Two new families of Glomales, Archaeosporaceae and Paraglomaceae, with two new genera Archaeospora and Paraglomus, based on concordant molecular and morphological characters

Two ancestral clades of arbuscular mycorrhizal fungal species were discovered from deeply divergent ribosomal DNA sequences. They are classified here as two new families Archaeosporaceae and Paraglomaceae. Each family is phylogenetically distant from each other and from other glomalean families, despite similarities in mycorrhizal morphology and fatty acid profiles. Shared mycorrhizal morphology is not surprising, since it is highly conserved and resolves other taxa in Glomales at both family and suborder levels. At the present, time, each family consists of one genus. Archaeospora (Archaeosporaceae) includes three species forming atypical Acaulospora-like spores from sporiferous saccules. Two of these species are dimorphic, forming Glomus-like spores as well. Paraglomus (Paraglomaceae) consists of two species forming spores indistinguishable from those of Glomus species. Morphological characters once considered unique, such as the sporiferous saccule defining species of Acaulosporaceae, clearly are distributed in phylogenetically distant groups. The simple design of spores of some species in Glomus also masks considerable divergence at the molecular level. It is the combination of DNR sequences, fatty acid profiles, immunological reactions against specific monoclonal antibodies, and mycorrhizal morphology which provides the basis for recognizing Archaeospora and Paraglomus. These results reinforce the value of molecular data sets in providing a clearer understanding of phylogenetic relationships, which in turn can lead Co a more robust taxonomy.