Social Learning and Sexual Selection in Field Crickets

This proposal addresses a central concept in evolutionary biology regarding the origin and maintenance of biological diversity through sexual selection. Sexual selection via female choice can accelerate reproductive isolation in diverging populations, and its role in driving the elaboration and maintenance of male ornaments is supported theoretically and empirically. All theoretical frameworks for sexual selection rely on the genetic basis of female preferences and male ornaments. However, a number of non-genetic factors have captured the attention of researchers because of their potentially large effects on the strength and direction of sexual selection. One of these has recently gained attention: plasticity in female mate choice. Mate choice is the process by which females evaluate the attractiveness of available males and make a decision about who to mate with. Mate choice plasticity refers to flexibility in individual mating behavior that is influenced by environmental factors. This proposal focuses on how social information learned from conspecifics contributes to such flexibility in mate choice, and I am ultimately interested in how changes in mate choice feed back to alter selection pressure on male traits. My research will use an insect system, because although insects are extensively used as models in sexual selection studies, information about how social learning affects insect mate choice and sexual selection is lacking. I will pursue this fruitful avenue of inquiry using the Polynesian field cricket Teleogryllus oceanicus. I will investigate population-level variation in socially-learned mate choice plasticity, its genetic basis and fitness effects on individuals, and its broader implications for sexual selection pressure on male traits. My postdoctoral work at the University of California, Riverside has established that female crickets can retain information about the attractiveness of calling males and use that information to alter subsequent mating decisions. Given this foundation, my first goal is to investigate the extent to which mate choice plasticity varies on a population-wide scale. Theoretical arguments suggest that founding populations in new environments will be selected to exhibit a greater degree of adaptive phenotypic plasticity. The social environment of newly-founded populations would be expected to vary stochoastically, and I will test the hypothesis that more recently founded populations (inferred using population genetic data) show a greater degree of socially-mediated mate choice plasticity. Second, I will perform a quantitative genetic mating experiment to detect genetic variation in the tendency of females to respond to different social environments by altering their mating behavior. My analysis will detect whether females of different genetic backgrounds show asymmetrical behavioral responses to social experience. This will reveal the potential for selection to act on socially-mediated mate choice plasticity, which depends on the magnitude of additive genetic variation for it. Third, I will examine fitness consequences of socially-mediated mate choice plasticity in the field. This analysis will lend key insights into how social effects alter sexual selection pressure in the wild, which has not been addressed in empirical studies to date. Finally, I will develop quantitative genetic models of sexual selection that incorporate socially-mediated mate choice plasticity, to test how such plasticity alters the outcome of sexual selection. The theoretical models will address the opposing hypotheses that experience-mediated plasticity in mate choice can strengthen vs. weaken sexual selection, and will explore the question of whether selection on mate choice plasticity can drive the evolution of reproductive barriers between populations.