Although Fungi imperfecti/Deuteromycota is no longer formally accepted as a
taxon, many of the fungi it included have yet to find a place in modern fungal classification. This is because most
fungi are classified based on characteristics of the fruiting bodies and spores produced during sexual reproduction, and members of the Deuteromycota have been observed to reproduce only asexually or produce no spores.
Mycologists formerly used a unique dual system of nomenclature in classifying fungi, which was permitted by Article 59 of the
International Code of Botanical Nomenclature (the rules governing the naming of plants and fungi). However, the system of dual nomenclature for fungi was abolished in the 2011 update of the Code. Under the former system, a name for an asexually reproducing fungus was considered a
form taxon. For example, the ubiquitous and industrially important mold,
Aspergillus niger, has no known sexual cycle. Thus
Aspergillus niger was considered a form taxon. In contrast, isolates of its close relative,
Aspergillus nidulans , revealed it to be the anamorphic stage of a
teleomorph (the
ascocarp or fruiting body of the sexual reproductive stage of a fungus), which was already named
Emericella nidulans. When such a teleomorphic stage became known, that name would take priority over the name of an
anamorph (which lacks a sexual reproductive stage). Hence the formerly classified
Aspergillus nidulans would be properly called
Emericella nidulans – note there's no reference to the original author. The system since 2013 instead treats both as the same species typified by the anamorph, and hence the author citation would include the original author as
Emericella nidulans ==Phylogeny and taxonomy==