Species diversity, updated classification and divergence times of the phylum Mucoromycota

Zygomycetes are phylogenetically early diverging, ecologically diverse, industrially valuable, agriculturally beneficial, and clinically pathogenic fungi. Although new phyla and subphyla have been constantly established to accommodate specific members and a subkingdom Mucoromyceta, comprising Calcarisporiellomycota, Glomeromycota, Mortierellomycota and Mucoromycota, was erected to unite core zygomycetous fungi, phylogenetic relationships within phyla have not been well resolved. Taking account of the information of monophyly and divergence time estimated from ITS and LSU rDNA sequences, the present study updates the classification framework of the phylum Mucoromycota from the class down to the generic rank: three classes, three orders, 20 families (including five new families Circinellaceae, Protomycocladaceae, Rhizomucoraceae, Syzygitaceae and Thermomucoraceae) and 64 genera. The taxonomic hierarchy was calibrated with estimated divergence times: phylum earlier than 617 Mya, classes and orders earlier than 547 Mya, families earlier than 199 Mya, and genera earlier than 12 Mya. Along with this outline, all genera of Mucoromycota are annotated and 58 new species are described. In addition, three new combinations are proposed. In this study, we update the taxonomic backbone of the phylum Mucoromycota and reinforce its phylogeny. We also contribute numerous new taxa and enrich the diversity of Mucoromycota.