Developmental plasticity induced by heat waves in a predator-prey system

Climate change is considered to affect the characteristics of heat waves by increasing their duration, frequency and intensity, which is a challenge for ectothermic species such as arthropods in relation to juvenile survival and development. However, arthropods may respond to heat waves via developmental plasticity, which may have differential consequences on a predator and its prey. We evaluated this assumption by using the predatory mite Phytoseiulus persimilis and its preferred prey, the spider mite Tetranychus urticae, which are prominent counterparts in biological control. Individuals of both species were separately exposed to mild and extreme heat waves for their whole juvenile development. Both species developed faster during extreme heat waves. Relatively, spider mites were able to accelerate their juvenile development more than the predator, which could reduce the exposure time of susceptible developmental stages to heat waves and predators. Prey and predator males and predator females, but not prey females, reached smaller body sizes under extreme heat waves, which resulted in a shifted female predator-prey body size ratio in favor of the female prey. This could have positive effects for the prey females as being large usually results in higher longevity, fertility, heat resistance and possibly lower predation rates. Hence, our results suggest that the pest could gain advantages during the development in comparison to the predator via developmental plasticity, which may also lower the control success of P. persimilis on the prey T. urticae under extreme heat wave conditions.