Theoretical and Empirical Studies of Information Gathering and Decision Making in Threespine Stickleback (Gasterosteus aculeatus) Female Mate Choice
Mate choice studies typically consider how sexual selection shapes mate preferences and corresponding traits. Through theoretical models and empirical studies of the threespine stickleback, my dissertation shifts the focus to the mate choice process, which includes information gathering and decision making under time and energy costs.
I construct a model (Comparative Bayes) that allows females to choose a mate or selectively gather information about potential mates. Bayesian updating combines prior information about male quality with new information gained from assessment, thus relaxing assumptions of previous models (namely, that females randomly encounter and gain perfect information about males). I find that females should selectively gather information from males that are less familiar, have clearer signals, and cost less to assess. The model generates patterns of female encounters with males similar to those observed for several species and produces higher female fitness than previously proposed mate choice models.
I study the mate choice process and test the Comparative Bayes model in threespine sticklebacks. My field and enclosure observations show that females actively initiate courtships, court with multiple males, and regularly revisit males. The costs of gathering information were manipulated in an experiment that allowed stickleback females of different states (reproductive and energetic) to choose between two males. Females held gravid longer before trials were more likely to respond positively to male courtship initiations. Females forced to swim against a current before trials were more likely to continue courtships and enter a male's nest, and took less time to do so.
I also develop a model examining how female peacock wrasse (Symphodus tinea) should utilize experience when making reproductive decisions. Females can choose to search for and spawn with nesting males or forgo costly searching and spawn with non-nesting males. Benefits of searching change as the availability of nesting males varies over the breeding season. When there is predictable or unpredictable variation within or between breeding seasons. using experience to estimate the probability of successfully searching for nesting males is better than having a fixed estimate shaped by selection. Females should optimally forget older experiences, however, with the rate of environmental change.