Abstracts (first author)
Host allelic diversity drives long-term host-parasite coevolutionary dynamics
Background: Hosts and parasites are involved in a coevolutionary interaction in which hosts do not evolve as fast as their parasites. Yet, fast adaptive genetic changes occur upon infection, especially if host-parasite interactions are characterized by Red Queen dynamics. Red Queen dynamics between both antagonists are caused by negative frequency-dependent selection and are assumed to have constant amplitudes. Here, a long-term time shift experiment, based on a unique historical reconstruction of a Daphnia-parasite coevolution, reveals that infectivity cycles with a smaller amplitude in experienced than in naive hosts. Experienced hosts were isolated from recent time periods, naive hosts from past time periods. A coevolution model, incorporating an increase in allelic diversity over time in the host confirmed the asymmetry in the infectivity cycles. In contrast, increased virulence over time did not confirm the observed experimental results. The accumulation of resistance alleles affects long-term Red Queen dynamics. Long-term effects in host-parasite coevolution have so far been neglected, but this reconstruction in combination with a theoretical study on long-term time shifts between a host and a parasite extends current insight into the dynamics of co-evolutionary antagonistic interactions.