Date of Completion


Embargo Period



Threespine Stickleback, Gasterosteus aculeatus, alternative reproductive tactics, sneaking, behavioral plasticity

Major Advisor

Carl D. Schlichting

Co-Major Advisor

Susan A. Foster

Associate Advisor

Eric T. Schultz

Associate Advisor

Kentwood D. Wells

Field of Study

Ecology and Evolutionary Biology


Doctor of Philosophy

Open Access

Open Access


Behavior, a group of highly plastic and responsive phenotypic traits, has been characterized as having the potential to both drive and inhibit evolutionary change within populations. The Threespine Stickleback radiation (Gasterosteus aculeatus L.) is a model system that demonstrates the vital role environment plays in behavioral evolution – with multiple colonizations of variable freshwater habitats by ancestral oceanic metapopulations producing the behaviorally diverse populations observable today. Here I characterize both inter- and intra-population variation in sneaking behavior – an inconspicuous mating tactic used by threespine males to gain fertilizations as an alternative to courtship behavior. I present evidence for regional and population-level variation in sneaking frequencies under natural conditions in the Pacific Northwest of North America. Using common garden laboratory techniques to determine the extent to which the difference in sneaking propensities observed under field conditions are genetically versus environmentally influenced, I found sneaking behavior retained in populations not observed to express this tactic under natural conditions. Individuals within and among populations also demonstrated variation in sneaking propensity, behavioral consistency, and tactic flexibility/plasticity. Lastly, I investigated the extent to which body size, condition, or coloration and patterning often associated with the sneaker tactic is specifically characteristic of this behavioral tactic in an Alaskan freshwater population and found no evidence of tactic specific physical traits. This collection of studies provides exciting results, as the flexibility in tactic expression and body coloration observed suggests that complex decision-making rules underlie reproductive tactic use in stickleback.