Are transmission modes important for the evolution of mutualistic symbioses?
Evolutionary theory suggests that hosts and symbionts in asymmetrical symbioses may conflict over patterns of symbiont transmission. Selection favours symbionts to disperse out of the vertical host lineage. The subsequent decrease in relatedness between symbionts favours within-host competition and virulence. Hosts are therefore expected to favour reduced mixing of their symbionts, because horizontal transmission is expected to be associated with parasitic symbiont traits. However, numerous examples of mutualistic symbioses exist where horizontal transmission is the rule. In this symposium the most recent insights, both theoretical and empirical, on the importance of transmission modes for the outcome of mutualistic symbioses, will be presented.
