Crossing the line: selection and evolution of virulence traits

Abstract

The evolution of pathogens presents a paradox. Pathogenic species are often absolutely dependent on their host species for their propagation through evolutionary time, yet the pathogenic lifestyle requires that the host be damaged during this dependence. It is clear that pathogenic strategies are successful in evolutionary terms because a diverse array of pathogens exists in nature. Pathogens also evolve using a broad range of molecular mechanisms to acquire and modulate existing virulence traits in order to achieve this success. Detailing the benefit of enhanced selection derived through virulence and understanding the mechanisms through which virulence evolves are important to understanding the natural world and both have implications for human health.

Figure 1. Flow Diagram of a Generic Pathogen Life Cycle Indicating the Selective Pressures That Have Been Suggested or Shown to Be Important in Shaping Pathogen Virulence

The filled ellipse represents host species A (the major host), and the filled rectangle represents host species B (the novel host).