Date of Award:

5-2024

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Watershed Sciences

Committee Chair(s)

Edward Hammill

Committee

Edward Hammill

Committee

Trisha Atwood

Committee

Timothy Walsworth

Committee

Peter Adler

Committee

Kezia Manlove

Abstract

Ecology is studied at multiple scales to better understand how small changes at the individual level scale up to affect our ecosystems and global systems. These ecological scales include individuals (single organism), populations (group of organisms of the same species), communities (populations of different species interacting with each other), and ecosystems (species interacting with other species and their local environment). The research in this document is focused on the individual, population, and community scale. In particular, this research addresses questions regarding how changes in environmental conditions (i.e., predation and resources) affect species interactions which ultimately affects the composition of ecological communities in aquatic systems. We aimed to answer the question, how do changes in both predation pressure and available resources affect prey defense strategies, and how do changes in these prey defense strategies scale up to affect populations and ecological communities. By utilizing a protist-flatworm system in a lab setting and an aquatic macroinvertebrate (i.e., larval bugs) system in Costa Rica, we found both predicted and unexpected results. In particular, we found that when altering both the number of predators and the amount of a resource, there were key moments when prey were choosing to invest in defense strategies (protection from increased predation threat) over investing in reproduction, and vice versa. Additionally, we found that these same prey defense strategies demonstrated the potential to stabilize populations that were experiencing instability from an influx of nutrients. Within the macroinvertebrate system, we found that altering predator presence and leaf litter (proxy for resources) both affected what taxa abundance in aquatic communities, however, there were no clear patterns across all taxa. By investigating the effects of changing environmental conditions on individuals, populations, and ecological communities, our research adds clarity and additional information on how future environmental changes may affect communities of organisms at the local, regional, and global scale.

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