Melanospora (Sordariomycetes, Ascomycota) and its relatives

The order Melanosporales comprises a large group of ascomycetes, most of them mycoparasites, characterized by the production of usually ostiolate, translucent ascomata, unitunicate asci, and unicellular, pigmented ascospores with germ pores or germ slits. The most studied taxa areMelanosporaandSphaerodes, but the boundaries with other morphologically closely related genera are not well resolved. In this study, the taxonomy ofMelanosporaand related taxa have been re-evaluated based on the analysis of nuclear rDNA, actin and elongation factor genes sequences of fresh isolates and numerous type and reference strains. The genusMelanosporahas been restricted to species with ostiolate ascoma whose neck is composed of intermixed hyphae, and with a phialidic asexual morph.Microtheciumhas been re-established for species ofMelanosporaandSphaerodeswithout a typical ascomatal neck or, if present, being short and composed of angular cells similar to those of the ascomatal wall, and usually producing bulbils. Three new genera have been proposed:Dactylidispora, possessing ascospores with a raised rim surrounding both terminal germ pores;Echinusitheca, with densely setose, dark ascomata; andPseudomicrothecium, characterized by ascospores with indistinct germ pores. Dichotomous keys to identify the accepted genera of the Melanosporales, and keys to discriminate among the species ofMelanosporaandMicrothecium, as well as a brief description of the accepted species of both genera, are also provided.