Temperature Affects Chemical Defense in a Mite-Beetle Predator-Prey System

Temperature influences all biochemical and biophysiological processes within an organism. By extension, it also affects those ecological interactions that are mediated by gland-produced chemical compounds, such as reservoir-based chemical defense. Herein, we investigate how environmental temperature affects the regeneration of defensive secretions and influences the efficacy of chemical defense in a model predator-prey system: the oribatid mite Archegozetes longisetosus and the predaceous rove beetle Stenus juno. Through a combination of chemical analyses, non-linear regression modeling and theoretical simulations we show that the amount of defensive secretion responded to temperature in a unimodal optimum curve: the regeneration rate followed a positive, linear relationship up to 35 °C, but rapidly broke down beyond this temperature ("tipping point" effect). Using functional response simulations, there is an initially positive dampening effect on the predation rate when regeneration is optimal, but at higher temperatures chemical defense does not counteract the previously described effects of elevated predatory pressure. In a larger context, our results demonstrate the need to integrate relevant environmental factors in predator-prey modeling approaches.