Umbelopsidaceae (Meyer and Gams, 2003) includes fungi that were originally described as species of Micromucor, Mortierella, Mucor, or Umbelopsis. Gams (1977) described Mortierella subgenus Micromucor and he transferred six species and three varieties to the new subgenus. Later, von Arx (1982) elevated Micromucor from subgenus to genus, and he treated Umbelopsis, a genus described as deuteromycete (Amos and Barnett, 1966) that was later treated as a zygomycete related to the Mucoraceae or Thamnidiaceae (Mucorales) (von Arx, 1982). Three species ( M. isabellinus, M. longicollis, M. ramannianus ) were retained in the genus Micromucor and three species ( U. nana, U. roseo-nana, U. vinacea ) included in Umbelopsis.
Micromucor and Umbelopsis are distinguished morphologically because of differences in sporangiophore branching and columella formation; Umbelopsis also has a few species with unispored sporangia (von Arx, 1982). Yip (1986) said that the main reason for separating these two genera, sporangiophore length and branching cannot be used to separate Micromucor and Umbelopsis because short and long sporangiophores have been reported in M. isabellina (Turner, 1963). Yip (1986) then suggested that all species of Micromucor should be transferred to Umbelopsis. Also, some species of Umbelopsis can be highly variable morphologically (Kendrick et al., 1994).
Research was conducted to determine whether the affinities of Umbelopsis were with the Mortierellaceae or the Mucoraceae. It was later discovered that Umbelopsis ( Mortierella isabellina group) were most closely related to the Mucoraceae based on fatty acid (Amano et al., 1992), and composition comparison of antigenic extracellular polysaccharides (de Ruiter et al., 1993). Meyer and Gams (2003), using RFLP of the ITS region and ITS1 sequence comparison, reveal that the two sister clades in the M. isabellina group did not correspond with spore pigmentation or any morphological character and, therefore, all of these fungi are being treated as members of Umbelopsis; they also found that Umbelopsis is distantly related to the Mucoraceae but not to the Mortierellaceae. For these reasons the Umbelopsidaceae, containing only Umbelopsis, was proposed for members of the Mortierella isabellina group. One species, Mortierella longicollis, which is morphologically similar to members of Umbelopsis, may be a member of Mortierella and not Umbelopsis.
Umbelopsidiaceae W. Gams & W. Meyer, 2003 (in Meyer and Gams, Mycological Research 107:348).
Sporangiophores arising from a vesicle on the stipe, borne cymosely or verticellately, terminating in uni- or multispored, ochraceous to reddish sporangium that may or may not have a columella. Sporangiospores angular or not angular and variously shaped, the same color as the sporangia; appendaged in some species. Chlamydospores often abundant. Zygospores unknown.
Type and only genus: Umbelopsis.
Synopsis of Genera
UMBELOPSIS Amos & Barnett, 1966 (Mycologia 58: 807); 11 spp. (Amos and Barnett, 1966; von Arx, 1982; Yip, 1982, 1986a, 1986b; Meyer and Gams, 2003; Sugiyama et al., 2003; Mahoney et al., 2004).
Updated Feb 10, 2005