Advances in Phylogeny and Taxonomy of Glomeromycetes: Three New Orders, and Five New Families

The objective was to analyze the phylogeny and morphology of the Glomeromycetes on the order level hitherto consisting of Glomerales, Entrophosporales, Diversisporales and Gigasporales. The updated data sets show that Pacisporaceae is near to Gigasporales, but without support to place this family in Gigasporales or Diversisporales, while the Acaulosporaceae and Sacculosporaceae clades clearly separate from Diversisporaceae. The phylogeny indicates that Pacisporaceae should be transferred here to the new order Pacisporales. Morphologically, Pacisporales differ from all families in the Gigasporales by type of spore formation (on subtending hyphae instead on suspensors (= bulbi), by formation of vesicular-arbuscular mycorrhiza, and by germination characteristics. The phylogenetic analysis supports the separation of Acaulosporaceae and Sacculosporaceae from Diversisporales, from each other, and from all other Glomeromycetes orders. These two families are here transferred to Acaulosporales and Sacculosporales. Acaulosporales are characterized by spore formation in a clear distance of 50-250 µm from globose termini of sporiferous saccules and by the diagnostic, ‘beaded’ inner wall. In Sacculosporales, there is no distance between the spores and the saccule termini, and the inner wall is never ‘beaded’. Additionally, four new families are separated within the Glomerales, and one new family within the Diversisporales.