The use of DNA sequences in fungal taxonomy commenced three decades ago [1] and has improved our understanding of fungal diversity immensely. Nowadays, fungal taxonomy is relying on an integrative approach combining morphological and molecular phylogenetic data [2–8]. Still, hundreds of asexual genera are currently treated as “orphaned” genera, meaning they do not have a formal placement in family or other higher ranks [9, 10]. Most of the genera that lack DNA sequences are listed as Ascomycota genera incertae sedis. Nevertheless, a large number of hyphomycetous genera and several coelomycetous genera are linked with Basidiomycota [9]. In other words, it is questionable to conclude that all genera lacking DNA sequences belong in Ascomycota genera incerte sedis.
Taxonomists mainly use DNA sequences to introduce new species and resolve species complexes, to establish generic boundaries and resolve polyphyletic genera, to provide familial placement, and to link asexual and sexual genera following the principle of one fungus–one name. When fungal strains are selected for phylogenetic analyses, taxonomists try to include ex-type strains. It is essential to include ex-type strains of the type species for the representation of genera. This is common practice among taxonomists who work on both asexual and sexual fungi. However, still, there are many genera that lack DNA sequences for their type species or existing strains are not ex-type strains (including ex-epitype, ex-neotype).
It is possible to place sexual fungi in current classification systems without DNA sequences using most prominent morphological features such as number of ascus layers, apicular chambers, ascospore characteristics, etc. However, in the case of asexual fungi, it is essential to have DNA sequences to place them in family level or higher rank. The reason for this is that asexual genera a) have little discriminative morphological features and b) they show considerable morphologically plasticity. Some morphologically similar taxa could be phylogenetically distinct genera, e.g., Hormotomyces and Stilbospora fide [11, 12]; camarosporium-like taxa fide [13, 14]; Pithomyces and Pseudopithomyces fide [15].
Moving forward, it is important to revisit these “orphaned” asexual genera and study them with combined morphological and molecular analyses. Moreover, nomenclatural issues need to be addressed, because recent published data are scattered (e.g., a checklist for coelomycetes have not been published since Sutton) [16], and the one fungus–one name concept needs to be implemented [17]. It is important to make fresh collections of “orphaned” genera based on their originally reported hosts and compare morphology with the original protologue. Finally, the importance of studying fungi in tropical regions has been recognized as vital in the future of fungal taxonomy [18]. Hence, this type of studies will be helpful to continue one fungus–one name concept, which is one of the key stone areas in mycology in this era and also to clarify the global fungal species number.
