Graduation Semester and Year
Summer 2025
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Biology
Department
Biology
First Advisor
Matthew Walsh
Second Advisor
Laura Mydlarz
Third Advisor
Shane Dubay
Fourth Advisor
Luke Frishkoff
Fifth Advisor
Alison Ravenscraft
Abstract
Ecological variables can induce the stress response in organisms. Yet, few studies have tested for evolutionary shifts in stress responses across ecological gradients. In these studies, we used Trinidadian killifish found in sites with predators (high predation, HP) and sites where they are the only fish present (killifish only, KO). HP and KO populations differ in a suite of behavioral and life-history traits, making the Trinidadian killifish an excellent model to examine evolutionary physiology. My dissertation addresses the knowledge gap by examining: (1) how baseline cortisol differs in wild-caught Trinidadian killifish found in HP and KO sites, (2) the influence of the direct and indirect effects of predation on the evolution of the stress response (cortisol levels) by rearing second-generation lab-born fish from sites with and without predators on contrasting food levels that reflect the known differences in growth between the communities, and (3) how divergent predation environments influence maternal effects on egg hormone levels and subsequent offspring performance. In chapter one, I demonstrate significant differences in baseline cortisol levels between HP and KO populations. I also observed variation across replicate rivers, potentially indicative of non-parallel divergence. In chapter two, I found that fish from sites with predators (HP) have evolved significantly lower baseline cortisol levels than fish that lack predators (KO). However, these differences were only apparent when fish were fed high food levels and disappeared under a low resource treatment that mimics growth in sites where predators are absent. Given the known differences in population density and resource availability between HP and KO sites, our results indicate that both the direct and indirect consequences of predation shape the evolution of the stress response. In chapter three, our findings revealed that KO females deposited higher levels of triglycerides and cortisol into their eggs, which was associated with reduced offspring growth. In contrast, HP females exhibited more moderate levels of deposition and evidence of a physiological buffering mechanism mitigating the negative impact of elevated cortisol. These results suggest that maternal transfer strategies are shaped by population-specific ecological histories, particularly the presence or absence of predators.
Keywords
Ecology, Evolution, Cortisol, Killifish, Maternal Effects
Disciplines
Behavior and Ethology | Comparative and Evolutionary Physiology | Evolution | Other Ecology and Evolutionary Biology
License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Recommended Citation
Feder, Mikaela E., "THE EVOLUTION OF THE STRESS RESPONSE IN THE TRINIDADIAN KILLIFISH: ECOLOGICAL DRIVERS AND MATERNAL MEDIATION" (2025). Biology Dissertations. 231.
https://mavmatrix.uta.edu/biology_dissertations/231
Included in
Behavior and Ethology Commons, Comparative and Evolutionary Physiology Commons, Evolution Commons, Other Ecology and Evolutionary Biology Commons