Figure 1.

Conceptual illustration of predictions regarding patterns of local adaptation across space and time and the potential to uncover host local adaptation, even when parasites are locally adapted in contemporary time. (a) Example of host local maladaptation (and parasite local adaptation) against contemporary parasites from sympatric populations relative to allopatric populations. Such a pattern would be expected when host resistance is specific to local phage-mediated selection. (b) Example of no pattern for host local adaptation or maladaptation as would expected when adaptations conferring host resistance are general. (c,d) Example of time-shift experiment in which hosts are challenged with sympatric parasites from either the contemporary time point (0) or earlier points in time (−1 to −3). The difference between predictions based on a coevolutionary model of fluctuating selection dynamics (FSD; c) versus arms race dynamics (ARD; d) is illustrated. (e) Example of host local adaptation when tested against sympatric (black, solid lines) and allopatric (grey, dashed lines) parasites from the past. In this case, the hosts are maladapted to their contemporary parasites (consistent with (a)) and show higher resistance against parasites from the recent past (consistent with (c)). (f) Example where no host local adaptation or maladaptation is observed, even when tested against parasites from the past. In this case, the hosts are neither adapted nor maladapted to their contemporary parasites (consistent with (b)) and show higher resistance against parasites from all past time points (consistent with (d)).