From Individuals To Communities: The Effect Of Climate Change On Ectothermic Predators
Abstract
The living components of ecological systems exist within a nested hierarchy, consisting of individuals, populations, and communities. Because of this nestedness, climate change can greatly impact ecological systems, as whole-organism metabolic and physiological demands change for ectotherms under warming, the effects of which may compound with every succeeding level. Therefore, a multi-level approach can better isolate how climate change will reshape ecological systems. In my doctoral research, I used feeding and mesocosm experiments to examine how climate change affects ectothermic predators at the individual-, population-, and community-level, using mesostigmatic mites (Arachnida: Parasitiformes) as my model predator. My research objectives were to: 1) determine how climate warming affects predator feeding rate and behaviour, 2) test how temperature variability across two temperature ranges impacts predator populations and predator-prey interactions, and 3) identify how short-term intensive warming affects the assemblage composition of mesostigmatic mites from boreal forest soils. In my feeding experiments, I found that the predator mite Stratiolaelaps scimitus increasingly fed on small-bodied but not large-bodied prey under warming, which lowered their estimated energy intake. I hypothesize predators prioritized lower handling costs, rather than maximize energy gain to offset higher metabolic demands. Furthermore, I found that greater exposure of predators (and prey) populations to warmer temperatures (20 °C+) strengthened predator-prey interactions but most notably, predators consistently increased the average size of prey within their populations when exposed to warmer temperatures. Finally, I observed that short-term intensive warming shifted soil Mesostigmata assemblages, which was primarily due to the increased abundance of a single asexual species, Veigaia mitis. Increased abundances of asexual species under warming have not been previously reported for microarthropod predators. Across my experiments, body size, of either predators or prey, factored into how temperature increase affected ectothermic predators and predator-prey interactions. This underlines the significance of individual size in ectothermic predator-prey dynamics, but more broadly, that alterations to ecosystem-level functions may be attributed, either directly or indirectly, to changing body size distribution. Future research should further examine the relationship between ectothermic predator and prey body size and ecosystem functions to understand how climate change will affect ecological communities.