Abstracts (first author)
Lotka and Volterra kill the Red Queen
Author(s): Schulenburg H, Gokhale CS, Papkou A, Traulsen A
Host-parasite coevolution is generally believed to follow so-called Red Queen dynamics consisting of ongoing oscillations in the frequencies of interacting host and parasite alleles. This view is based on current empirical and theoretical work, which specifically focuses on the evolutionary dynamics of these interactions (i.e., the change in host and parasite allele frequencies). Here, we demonstrate that consideration of a central ecological component, population size fluctuations, dramatically alters these dynamics. In particular, reciprocal selection among antagonists causes inter-dependent demographic variations, as described by the Lotka-Volterra relationship. These population size fluctuations are thus an inherent characteristic of host-parasite coevolution. As they associate with repeated bottlenecks, they increase the likelihood of genetic drift. This in turn favours fast fixation of one of the interacting alleles, often including the allele that is originally rare. As a consequence, any ongoing Red Queen dynamics is rapidly terminated. Taken together, our results suggest that host-parasite coevolution is mainly driven by selective sweeps rather than continuous negative frequency-dependent selection. Long-term coevolution consistent with the Red Queen hypothesis is only possible if new alleles are repeatedly introduced de novo into the interacting host and parasite populations.