Fig. 6: Generalized model of strain heterogeneity and its relevance to the pathogenic potential of fungal strains.

Reference strain model: Conventional, reference-based approach whereby all strains of a fungal species are assigned the phenotypic features from a reference strain. This typological or essentialist approach contracts the phenotypic space of any species around that of the reference strain. In rapidly evolving species, this approach may spuriously associate strain-specific characteristics (e.g., genotype or metabolic profile) with a phenotype-of-interest (e.g., pathogenic potential) that is characterized only in the reference strain. This problem can be further exacerbated when reference stains are chosen based up their extreme phenotypes. Under this view, examination of the reference strains from two closely related species, one of which is a pathogen and one of which is non-pathogenic, reveals a large difference in their pathogenic potential. Pangenome/panphenome model: A more comprehensive, population-level characterization of genetic and phenotypic traits across a diversity of strains. This approach stems from “population thinking”¹¹⁷. In the context of pathogenicity, a population-thinking approach will increase emphasis of the reality of genetic and phenotypic variation exhibited by individual strains and can more fully capture the potential overlap (or its absence) in the pathogenic potential of closely related species.