Investigating the mechanism of a non-consumptive effect of a predator on the disease dynamics of its prey

Predators frequently affect their prey through non-consumptive pathways. These non-consumptive effects can cause shifts in behavior and physiology that alter the disease dynamics in the prey population. In the Chaoborus–Daphnia–Metschnikowia predator–prey-host–pathogen system, the presence of Chaoborus cues increases the susceptibility of Daphnia to infection by Metschnikowia, but the mechanism of this effect is yet unknown. This study investigated two potential mechanisms. Firstly, authors previously observing the non-consumptive effect on infection have hypothesized, but not directly tested, that it is the result of increased feeding rate, either due to increased foraging behavior or due to increased body size in the presence of the cue. Secondly, I hypothesize that the morphological defenses reported to be produced in the presence of Chaoborus kairomone cause a resource allocation trade-off between defense production and immune function. I tested these hypotheses by rearing Daphnia in a factorial design in the presence/absence of Chaoborus kairomone and the presence/absence of Metschnikowia spores, measuring life history traits, morphology, and feeding rate. My results did not support either hypothesis. While kairomone increased infection rate, feeding behavior did not increase, nor did body size. Morphological defenses were not produced in response to the kairomone, yet infection still increased. While the mechanism of the Chaoborus kairomone on Daphnia infection remains unknown, I have tested and rejected two likely hypotheses as to its functioning.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Entomology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Hearon, Luke

Contributors dc:contributor

• Cáceres, Carla
• Allan, Brian
• Dolezal, Adam

• Predator-prey
• Entomology
• Kairomone
• Infochemical
• Disease Ecology
• Trade-off

Statement dc:rights

• Copyright 2023 Luke Hearon

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/120147

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F120147