Temporal niche differentiation of parasites sharing the same plant host: oak powdery mildew as a case study

Plant diseases are often caused by complexes of closely related parasite species. The coexistence of species sharing the same niche challenges the competitive exclusion principle. Here, we performed the mathematical analysis of a generic model of sibling parasite species coexistence based on seasonality. We showed that coexistence through temporal niche partitioning is biologically plausible as it occurred in a significant part of the parameter space of the model. Moreover, the reversal of species relative frequencies (i.e., the most frequent species at the beginning of the season becoming the last frequent at the end) can occur without compromising the long-term coexistence of the two species. We provided data showing that this reversal pattern does repeat over years in the case of two sibling species responsible for oak powdery mildew (Erysiphe alphitoides and Erysiphe quercicola) in Europe. Last, the model was fitted to the data and satisfactorily described the population dynamics of oak powdery mildew species. The seasonal succession of these two plant pathogen species provides one of the few examples of coexistence by temporal niche partitioning at the scale of the season caused by exploitative competition. We discuss whether evolutionary branching may have led to temporal niche differentiation in this system.Une approche basée sur les traits d'histoire de vie des champignons phytopathogènes pour faire le lien entre fitness individuelle et stratégies écologiques