Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Biology

Supervisor

Lindo, Zoë

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.

Summary for Lay Audience

The living components of ecological systems are organized into three hierarchical levels: individuals, populations, and communities. Individuals from a single species make up a population, and populations from various species interact with one another in communities. Climate change is increasing global temperatures, which will alter ecological ecosystems and the organisms that inhabit them, which predominantly are ectothermic. Ectotherms are defined as organisms that rely on environmental temperatures to regulate their internal body temperature, meaning metabolic and physiological rates (e.g., feeding, growth, and movement) will change under warming. In my doctoral research, I examined how climate change affect ectotherms, specifically ectothermic predators, using lab-based feeding and mesocosm experiments, with mesostigmatic mites (Arachnida: Parasitiformes) as my model predator group. Mesostigmatic mites are small, highly diverse arachnids, who are commonly found in soil habitats and are often sold as biocontrol agents. Because of their diversity, abundance, and small body size, mesostigmatic mites are fitting model organisms to address this question. At the individual-level, I found that predator mites altered their feeding rate by consuming more small-bodied prey, but not large-bodied prey, under warming. At the population-level, I found that predators lowered prey population abundances with the effect appearing stronger at higher temperatures. Furthermore, average body length and body size distribution of prey was both temperature- and predator-dependent. At the community-level, I found that mesostigmatic abundance increased greatly under warming, which was primarily due to a single species, Veigaia mitis. Unlike other mesostigmatic mite species, Veigaia mitis is asexual, meaning populations contain only females, suggesting a reproductive benefit for asexual species at higher temperatures. Together, my doctoral research shows that climate change will affect ectothermic predator feeding behaviour, predator-prey interactions, and predator community composition, and climate change will greatly reshape ecological systems at multiple ecological levels.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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