Data from: Host life-history and host-parasite syntopy predict behavioral resistance and tolerance of parasites

There is growing interest in the role that life-history traits of hosts, such as their “pace-of-life”, play in the evolution of resistance and tolerance to parasites. Theory suggests that, relative to host species that have high syntopy (local spatial and temporal overlap) with parasites, host species with low syntopy should have lower selection pressures for more constitutive (always present) and costly defenses, such as tolerance, and greater reliance on more inducible and cheaper defenses, such as behavior. Consequently, we postulated that the degree of host-parasite syntopy, which is negatively correlated with host pace-of-life (an axis reflecting the developmental rate of tadpoles and the inverse of their size at metamorphosis) in our tadpole-parasitic cercarial (trematode) system, would be a negative and positive predictor of behavioral resistance and tolerance, respectively. To test these hypotheses, we exposed seven tadpole species to a range of parasite (cercarial) doses crossed with anesthesia treatments that controlled for anti-parasite behavior. We quantified host behavior, successful and unsuccessful infections, and each species’ reaction norm for behavioral resistance and tolerance, defined as the slope between cercarial exposure (or attempted infections) and anti-cercarial behaviors and mass change, respectively. Hence, tolerance is capturing any cost of parasite exposure. As hypothesized, tadpole pace-of-life was a significant positive predictor of behavioral resistance and negative predictor of tolerance, a result that is consistent with a trade-off between behavioral resistance and tolerance across species that warrants further investigation. Moreover, these results were robust to considerations of phylogeny, all possible re-orderings of the three fastest- or slowest-paced species, and various measurements of tolerance. These results suggest that host pace-of-life and host-parasite syntopy are powerful drivers of both the strength and type of host defense strategies against parasites. Future research should evaluate how often and how strongly host pace-of-life and host-parasite syntopy are correlated and which is the better predictor of the strength and type of host investments in anti-parasite defenses