The impact of host longevity on disease transmission: host-pathogen dynamics and the evolution of resistance.

摘要

Questions: How do disease transmission rates, host longevity, and spatial structure interact to determine disease dynamics and evolution of host resistance in systems where host sterility is the major consequence of infection? Features of model: A spatially explicit two-dimensional simulation model with deterministic within-population birth and death processes, but stochastic among-population dispersal. The model assumes frequency-dependent disease transmission and is loosely based on the pollinator-transmitted anther-smut fungus Microbotryum violaceum, which infects and sterilizes host plants in the Caryophyllaceae. Resistance varies among host individuals and is associated with a fitness cost. Ranges of key variables: Simulations were run over ranges of host death rates, disease transmission rates, and spatial structures observed in natural host species, i.e. Silene latifolia, S. dioica, S. acaulis and Lychnis alpina [S. suecica]. Conclusions: The simulation model predicts that: (i) increasing host longevity and connectivity of host patches is likely to select for pathogen strains with lower transmission rates; (ii) when hosts are short-lived or populations are isolated, susceptible genotypes with higher reproductive output may have a selective advantage even when disease is widespread; (iii) when hosts are longer-lived or populations are more connected, resistance costs are lower and resistance can evolve to higher levels. Existing data from natural host-pathogen systems support these conclusions, although predictions about resistance patterns need to be tested in future studies..