Wildlife provisioning selects for higher pathogen virulence in hosts with incomplete immunity

Abstract

AbstractAnthropogenic food provisioning provides massive inputs of food to wildlife, with profound ecological and evolutionary consequences. By altering wildlife condition, density, and behavior, provisioning can influence transmission of infectious diseases and thus may impose strong selection pressure on wildlife pathogens. But surprisingly, we lack theory on the eco-evolutionary consequences of provisioning for host-pathogen dynamics. Here we develop a mathematical model of the eco-evolutionary dynamics of a wildlife pathogen under provisioning, motivated byMycoplasma gallisepticum, a bacterial pathogen that emerged, spread, and changed its virulence in provisioned house finches. We model how provisioning influences the evolution of pathogen virulence, defined here as mortality associated with infection. Consistent with past empirical work, house finches recover from infection and acquire incomplete immunity; this incomplete immunity is stronger if their initial infection was with a more virulent pathogen strain. We find that, even though provisioning improves body condition, it should still select for higher virulence, and thus may actually lead to declines in host populations. These negative effects arise because provisioning magnifies the impact of incomplete immunity, selecting for higher virulence and driving host populations down. Our results highlight that food provisioning can select for more virulent pathogens, with potentially far-reaching implications for conservation.