The presence of generalist plant pathogens might not explain the long-term coexistence of plant species

Pathogens have been shown to contribute to the possibility of coexistence of competing plant species by creating ecological distinction between the coexisting species. This coexistence promoting mechanism resembles intra-specific density dependence as found in Lotka–Volterra models. However, plant species adapt in their level of resistance against pathogen infection and this adaptation has been shown to be traded-off by a reduction in growth rate. A model is developed to show that taking into account the possible adaptation of plant species to increase their resistance against pathogen infection by generalist pathogens has consequences for the coexistence of the plant species. The results show that in systems where plants adapt to the pathogen infection, coexistence becomes impossible. The implication of this finding is that plant pathogens might contribute less to the coexistence of plant species than is commonly thought.