The scale of competition impacts parasite virulence evolution

The structure of parasite populations can have important consequences for virulence evolution. Both the scale competition, whether it is more intense in within versus between host environment, and mode transmission, parasites transmit alone or groups hosts, influence population select changes virulence. In a selection experiment, we evolved metapopulations spider mite Tetranychus urticae, under local (fixed sampling per patch) global (sampling determined by patch productivity) with either co- (with female from same random different patches) transmission. After 33 generations evolution, fecundity each replicate was measured. Females ‘local-random’ regime were virulent higher than females ‘global-random’ regime. There no difference ‘global co-transmission’ regimes. These results show that not type impacted evolution T. urticae. Local competition may maintain levels genetic diversity at level metapopulation. As such, local, within-host, selected productive individuals better able to exploit their environment be one new host.