Announcing the Final Examination of John D. Konvalina for the degree of Doctor of Philosophy in Biology
Populations at the edge of the species range may adapt to stressful environments that occur at the range edge and exhibit genetic traits divergent from populations in the core of the species range. In this dissertation, I first examined how a stressor (salinity) has impacted genetic structure and demographic history in a wide-ranging, large semi-aquatic species, the American alligator (Alligator mississippiensis). I estimated the splitting of genetic clusters and matched them with geologic events of past sea level rise. Then, I tested whether coastal alligators were genetically adapted to high salinities compared to inland alligators. To do this I randomly placed juvenile alligators from coastal and inland populations in one of three salinities (0, 10, or 20 ppt) for two weeks. I collected behavioral, physiological, and histological datasets and found a gene by environment interaction, indicating genetic adaptation of coastal alligators to high salinities. Finally, I found that coastal and inland alligators exhibited differentially expressed genes in osmoregulatory organs in response to salt stress. Overall, my dissertation contributed to the study of adaptive evolution by demonstrating that salinity has been a past and current stressor for American alligators. As there appears to be evidence of convergent evolution for mechanisms to excrete salt in fully marine reptiles, my dissertation is starting to provide evidence for patterns of convergent evolution among reptiles that similarly use both freshwater and brackish water environments.
Committee in Charge: Eric Hoffman (Chair), Anna Savage, Pedro Quintana-Ascencio, Robert Fitak, Matthew Shirley
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