EFFECTS OF MATERNAL STRESS ON PHYSIOLOGY AND MORPHOLOGY
Open Access
- Author:
- Owen, Dustin
- Graduate Program:
- Ecology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- April 21, 2021
- Committee Members:
- Ephraim Hanks, Outside Field Member
Rudolf Schilder, Outside Unit & Field Member
Tracy Langkilde, Chair & Dissertation Advisor
Daniel Warner, Special Member
David Miller, Major Field Member
Jason Kaye, Program Head/Chair - Keywords:
- Lizard
Corticosterone
Stress
Sex Allocation
Maternal Effect
Heart Rate
Survival - Abstract:
- Environmental perturbations, such as the introduction of invasive species, can impose novel selective pressures on a variety of taxa. This can result in changes in fitness-relevant traits within an individual’s lifetime or across multiple generations that allow the species to better cope with the stressor. One important physiological response to the presence of a stressor is the release of hormones, such as corticosterone (CORT). CORT can trigger adaptive behavioral and physiological responses to a stressor, but prolonged exposure to CORT can have negative effects on the organism. Elevated levels of CORT in gravid females can also affect their offspring. Such maternal stress effects are becoming an increasingly important topic in the biomedical and ecological fields. Since maternal CORT can modify offspring traits, this could prepare offspring for high stress environments or, as is typically assumed in humans, could have detrimental effects on their health and survival. In our ever-changing world, understanding within- and cross-generational effects of exposure to novel stressors is critical to predicting and managing their consequences. My dissertation research tested the effects of CORT on various life stages and across generations using a system of native fence lizards (Sceloporus undulatus) and invasive fire ants (Solenopsis invicta). This is a useful system for testing this as fire ants are a newly introduced predator and prey of the lizards and represent a natural stressor that varies across populations, maternal CORT concentrations can be manipulated non-invasively, and fitness-relevant (i.e., health and survival) outcomes for mothers and offspring can be quantified. The endocrine-axis is highly conserved across all vertebrates, so the results of my research are applicable to other vertebrates, including humans. By manipulating CORT of gravid females, mimicking a naturally stressful encounter (e.g., with predators or heat stress), daily until they laid eggs, I was able to test the effects of this physiological response on traits of mothers and their offspring. The results of my dissertation research have contributed to our understanding of the effects of maternal CORT in three main ways. First, I reveal that maternal CORT impacts the physiology of offspring both within the egg and at 1 week old but does not impact the mother’s physiology. Second, I found that maternal CORT can alter offspring traits and allocation of resources from mother to offspring in sex-specific ways. Third, I show that the influence of stress within an organism’s lifetime is not as important as stress experienced across multiple generations. Overall, my dissertation addresses a number of important gaps in our understanding of the effects of maternal stress. The results of my work reveal that CORT produced in response to a stressor can affect how mothers allocate resources to their offspring, prioritizing daughters over sons, and can affect physiology (i.e., heart rate) of offspring even while still in the egg, which can affect survival relevant traits after hatching. I show that stress experienced by an individual’s ancestors trumps the stress experienced within its own lifetime with respect to the individual’s health and survival. Together, my research furthers our understanding of the factors that influence the health and survival outcomes of stress, which may also prepare offspring for the stressful environments they will be born into.