Source–sink dynamics of virulence evolution

Abstract

Source–sink models of adaptive evolution were initially used to study the population ecology of animals and plants. Here, the authors propose that such models can also be applied to the bacterial world and can help to understand how bacterial pathogens adapt to their human hosts. To understand the evolution of genetic diversity within species — bacterial and others — we must dissect the first steps of genetic adaptation to novel habitats, particularly habitats that are suboptimal for sustained growth where there is strong selection for adaptive changes. Here, we present the view that bacterial human pathogens represent an excellent model for understanding the molecular mechanisms of the adaptation of a species to alternative habitats. In particular, bacterial pathogens allow us to develop analytical methods to detect genetic adaptation using an evolutionary 'source–sink' model, with which the evolution of bacterial pathogens can be seen from the angle of continuous switching between permanent (source) and transient (sink) habitats. The source–sink model provides a conceptual framework for understanding the population dynamics and molecular mechanisms of virulence evolution.