Wang, Ying-Jie; Sentis, Arnaud; Tüzün, Nedim; Stoks, Robby
To date, we know a lot about the effects of global warming on individual species. Yet, in nature, species constantly interact with each other, for example predators hunting their prey. One way to cope with global warming is by evolving adaptations to higher temperatures. But how does the evolution of one species affect its interaction with another one? We tested this question using a well-known predator-prey system often encountered in freshwater ponds; the nymph of the blue-tailed damselfly feeding on the water flea. We used damselfly populations from France and Sweden. Due to the strongly differing thermal conditions between these two regions, French damselflies have evolved to adapt to conditions of higher mean temperatures, stronger heat waves, and more drastic temperature fluctuations during a day. By comparing the performance of French (low-latitude) damselfly larvae at their local summer mean temperature (24°C) to Swedish (high-latitude) damselfly larvae at their local summer mean temperature (20°C), we may discover how the Swedish damselfly larvae will respond to higher temperatures after thermal evolution.
In our laboratory experiment, we first tested how efficiently the damselflies from the two regions feed on water fleas from an intermediate latitude (Belgium), and whether this depends on the thermal conditions of the experiment. We found warming decreased the feeding efficiency of low-latitude predators at lower prey densities, and decreased the feeding efficiency of high-latitude predators at higher prey densities, except under daily temperature fluctuations. Next, we used a modelling framework to assess the long-term consequences of these predation patterns. We found warming weakened the long-term effect of the predator on the prey population density, except for the high-latitude predator-prey system with daily temperature fluctuations and during a heat wave. Finally, we evaluated how predator thermal evolution in high-latitude predator may contribute to shape the long-term consequences, by comparing the modelled long-term interaction of the high-latitude system at the high-latitude mean temperature to that of the low-latitude system at the low-latitude mean temperature. We found that thermal evolution may further weaken the long-term effect of the high-latitude predator on prey population density, even with daily temperature fluctuation and potentially also during a heat wave.
Our results underscore the importance of daily thermal fluctuations and heat waves in shaping predator-prey interactions, and suggest predator thermal evolution can shape how temperature affects predator-prey interactions.