Date of Graduation
Master of Science in Biology (MS)
Second Committee Member
damselfly, divergent selection, geometric morphometrics, local adaptation, morphology, phenotypic plasticity
Divergent selection across heterogenous environments could lead to adaptive divergence in populations resulting in potential local adaption. These populations have phenotypic differences that are fitness related and make native individuals more fit than non-native individuals. My research focuses on a species of damselfly, Enallagma exsulans, to explore local adaptation and morphological differences as a result of divergent selection or plasticity. My first study explored potential local adaptation of wild caught stream and lake E. exsulans using a reciprocal transplant design, a classic approach for this objective. The stream and lake sites chosen were on a small spatial scale allowing for potential gene flow among populations, a process that could hinder local adaptation. In the second part of my research, I reared stream and lake E. exsulans in a common garden and transplanted them into stream and lake environments. I expected to find that native individuals had higher fitness, measured as growth rates, than non-native individuals indicating local adaptation. Unfortunately, I was unable to collect any results due to a storm damaging my experimental set-up. There are still important questions about local adaptation occurring at small spatial scales with potential for gene flow, and if plasticity is another mechanism for coping with changing environments. In the next part of my study, I used individuals raised in a common garden environment for a small scale mesocosm reciprocal transplant replicating the field study. All larvae lost body mass, no matter the origin of the individual or the condition under which it was tested. I also completed geometric morphometric analyses of wild caught individuals from both stream and lake environments and common garden reared individuals to determine if morphological differences are the result of divergent selection between populations. In wild-caught individuals, I found significant differences in body and lamellae shape between lake and stream populations suggesting divergent selection. In common garden individuals, I did not detect significant differences, suggesting morphological divergence is not genetically based. Last, I completed behavioral assays with common garden individuals placing larvae into stream and lake conditions and scoring behavior, but no results were significant between lake and stream populations.
Graham, S. R. (2019). Do Enallagma exsulans from Streams and Lakes Show Patterns of Divergence?. Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/3229