Evolutionary relationships among mucoralean fungi (Zygomycota): Evidence for family polyphyly on a large scale

Mucorales (Zygomycota) are ubiquitous, morphologically simple terrestrial fungi that are united taxonomically by possession of a coenocytic mycelium upon which nonmotile mitotic spores are produced asexually in uni- to multispored sporangia, and zygospores, where known, are produced following fusion of sexually compatible hyphae. Here we report the first comprehensive phylogenetic analysis of essentially all genera of Mucorales (63 species, 54 genera and 13 families) based on partial nucleotide sequence data of nuclear small subunit (18S) ribosomal RNA and nuclear large subunit (28S) ribosomal RNA genes, translation elongation factor-1 alpha gene exons, and a morphological data set consisting of 1826, 389, 1092 and 11 characters, respectively. Individual and combined data sets were analyzed by unequally weighted maximum parsimony (MP) to investigate evolutionary relationships among and within mucoralean families. A Micromucor-Umbelopsis clade, traditionally included in the Mortierellaceae, was identified as the basal sister-group to all other Mucorales. A major discovery of this study is that traditional family-level classification schemes for this order appear to be highly artificial as evidenced by polyphyly of four of the seven families containing two or more genera. As presently circumscribed, these four families include 83% of the Mucorales. In addition, the largest and best known genera, Mucor and Absidia, were resolved as polyphyletic. The results provide a robust phylogenetic framework for additional evolutionary studies of the Mucorales.