Resistance genes affect how pathogens maintain plant abundance and diversity

Simon Maccracken Stump, James H. Marden, Noelle G. Beckman, Scott A. Mangan, Liza S. Comita

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Specialized pathogens are thought to maintain plant community diversity; however, most ecological studies treat pathogens as a black box. Here we develop a theoretical model to test how the impact of specialized pathogens changes when plant resistance genes (R-genes) mediate susceptibility. This work synthesizes two major hypotheses: the gene-for-gene model of pathogen resistance and the Janzen-Connell hypothesis of pathogen-mediated coexistence. We examine three scenarios. First, R-genes do not affect seedling survival; in this case, pathogens promote diversity. Second, seedlings are protected from pathogens when their R-gene alleles and susceptibility differ from those of nearby conspecific adults, thereby reducing transmission. If resistance is not costly, pathogens are less able to promote diversity because populations with low R-gene diversity suffer higher mortality, putting those populations at a disadvantage and potentially causing their exclusion. R-gene diversity may also be reduced during population bottlenecks, creating a priority effect. Third, when R-genes affect survival but resistance is costly, populations can avoid extinction by losing resistance alleles, as they cease paying a cost that is unneeded. Thus, the impact pathogens can have on tree diversity depends on the mechanism of plant-pathogen interactions. Future empirical studies should examine which of these scenarios most closely reflects the real world.

Original languageEnglish (US)
Pages (from-to)472-486
Number of pages15
JournalAmerican Naturalist
Issue number4
StatePublished - Oct 1 2020

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics


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