Abstract
AbstractPlant 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.
Highlights
Many widespread fungal plant diseases have long been attributed to a unique parasite species
The aim of this study was (1) to explore whether coexistence of sibling pathogen species through temporal niche partitioning is biologically meaningful, that is, whether coexistence occurs in a significant part of the parameter space of the generic model of species coexistence (Hamelin et al 2011); (2) to theoretically explore whether the reversal pattern in species frequencies during the season can occur without compromising long-term coexistence, which may seem unintuitive; (3) to test whether the reversal pattern is recurrent across years in the oak powdery mildew system (Feau et al 2012) and to fit the model to the time series of oak powdery mildew
We reported a new ecological finding: The reversal of the relative frequencies of the two species responsible for oak powdery mildew is recurrent across years
Summary
Many widespread fungal plant diseases have long been attributed to a unique parasite species. The advent of DNA sequence-based species identification techniques and the application of the phylogenetic species concept (Taylor et al 2000) has led to the increasing recognition that many current names of common fungal plant diseases mask complexes of sibling species (Fitt et al 2006). Such coexistence of closely related species that apparently occupy the same niche (the same host plant, and even the same organ) challenges the competitive exclusion principle (Gause 1934, Hardin 1960, Hutchinson 1961, Armstrong and McGehee 1980). Stuble et al (2013) showed that within a deciduous forest ant community, “ant species appear to temporally partition foraging times such that behaviorally dominant species foraged more intensely at night, while foraging by subdominant species peaked during the day.” Rarer still are examples of temporal niche partitioning at the scale of the season and through exploitative competition (occurring indirectly through a common limiting resource; Loreau 1989, Koide et al 2007, Winder 2009, Harabiš et al 2012)
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