6 - Coevolution of Host and Pathogen

Abstract

In this chapter, the process of host–pathogen coevolution is discussed. Oscillatory dynamics are key to many central theories regarding host–parasite coevolution, including both local adaptation and the maintenance of sexual reproduction. Common methods for examining pathogen adaptation to hosts, and host response to pathogens are explained with examples. The chapter explains that if mutation, recombination, migration rates, and population sizes are equivalent between hosts and parasites, then they are predicted to coevolve together at similar rates. An increase in any of these factors for both coevolving organisms is predicted to increase the rate of coevolution, as they will increase the genetic supply rate, shortening the time for reciprocal adaptation to occur. Generation time is also thought to be an important determinant of rate and strength of coevolution. In addition to the factors influencing the rate of population change, the trajectory and outcome of host–pathogen coevolution will be strongly influenced by both the community context and the abiotic environment in which it occurs. Several different methodologies have been used to test for coevolution between hosts and pathogens.