An Analysis of Individual Variation in Behavior

Emily Schmidt: An Analysis of Individual Variation in Behavior (Under the direction of Karin Pfennig) Individual animals within a population often show differences in their behavior. Recently, scientists have begun to study the causes and consequences of individual variation in behavior explicitly rather than attributing differences to observer error or noise. The study of behavioral syndromes, or correlated suites of behaviors, has become especially popular. Here I analyzed the fitness consequences of facultative hybridization-a behavior expressed by some individual female spadefoot toads-and evaluated the stability of a behavioral syndrome across development in the house cricket. First, I examined facultative hybridization in the spadefoot toad, Spea bombifrons. In Chapter 2, I used a split-clutch design to compare the development, morphology, and fitness of pure S. bombifrons tadpoles and their hybrid half-siblings. I found that hybrid tadpoles developed more quickly than pure S. bombifrons tadpoles, indicating that female S. bombifrons can benefit from hybridization. In Chapter 3, I then evaluated the mate preferences of female hybrid spadefoot toads. I found that hybrids preferred the calls of hybrid males over S. multiplicata males in deep water, but showed no preference in shallow water. Hybrids did not show a preference for S. bombifrons over hybrid or S. multiplicata calls in either context. These results indicate that female hybrid spadefoot toads show context-dependent mate choice, and express a maladaptive preference for the calls of sterile hybrid males in some environments. Finally, I measured boldness and exploration in juvenile, subadult, and adult European house crickets, Acheta domesticus, to iv determine if these behaviors comprise a behavioral syndrome in this species and if this syndrome differs between developmental stages. I found that boldness and exploration were positively correlated in subadult and adult crickets, but not in juvenile crickets. These results indicate that a behavioral syndrome linking boldness and exploration emerges later in development in the house cricket. Finally, I provide evidence that studies of personality in crickets can be successfully conducted in undergraduate lab courses. In sum, it is critical to analyze individual variation in order to fully understand the evolution of particular behaviors. v To my mom. Thank you for always believing in me. vi ACKNOWLEDGEMENTS