Dermatophytes: recognizing species of clonal fungi

Now that molecular data have forever changed our perspective on the anthropophilic and zoophilic dermatophyte species, the concepts of these species needs re-evaluation. In this paper, main concepts (morphological, biological (BSC), phylogenetic and genealogical concordance phylogenetic species recognition (GCPSR)) are compared. While in geophilic dermatophytes the application of the BSC works well for species distinction and is supported by molecular data, it is not applicable for the anthropophilic and zoophilic dermatophytes where the majority of species reproduce purely asexually. Also, the application of GCPSR (an operational method to define the limits of species using molecular, multi-locus data) is problematic. GCPSR can be applied in recombining fungi even when recombination is infrequent and fungi lack phenotypic sexuality. In truly clonal fungi, however, no incongruities in multi-locus data are found, and thus separation of species may be difficult. In fungi this problem is currently taken to be non-existent, since clonality is supposed to lead to extinction. In the medically relevant, host-associated dermatophytes, however, is reason to suggest that clonal dermatophyte lineages are able to maintain ongoing populations and to follow independent evolutionary trajectories. We distinguish seasonal, short-lived and long-lived clonal species. The final goal of a species concept, in the dermatophytes as well as in other fungi, is to provide a taxonomic system that reflects the evolution of the fungal species so that the underlying biological trends elucidated in this way may be brought forward to help to guide the clinician in applying optimal therapy and prophylaxis. The application of the different species concepts may have an enormous impact on the nomenclature of dermatophytes, directly affecting the quality of communications with care providers.