Phenotypic Variation in Mating Behavior and Reproductive Physiology
Mating and reproducing are key elements of fitness. Decisions made (consciously or not) during mating and reproducing have costs and benefits which may vary as a function of the contexts in which the decisions are made. In this dissertation, I explore associations between variation in two contextual factors (the social environment and the phenotypic state of focal individuals) and two aspects of mating and reproduction (mate preferences and reproductive investment). To address these associations, I perform common-garden experimental manipulations in Gryllus firmus crickets (Chapters 1 and 2), as well as a meta-analytical, synthetic review of primary empirical studies conducted on diverse taxa (Chapter 3). In Chapter 1, I show that manipulated variation in the social environment influences female reproductive investment in G. firmus female crickets: females exposed to male calling song (a sexual signal) built up their ovaries more rapidly in preparation for mating than did females exposed to silence (simulating an absence of available male mates). In Chapter 2, again working with G. firmus female crickets, I show that manipulation of phenotypic mating status (sexual experience versus inexperience) influences female sexual responsiveness (number of approaches to calling males) but not female preference functions (rankings of males varying in calling traits). Lastly, in Chapter 3 I perform meta-analyses of data from 144 primary publications on 112 species, and demonstrate a significant association between variation in mate preference components and variation in mate choosers’ phenotypic states (age, condition, mating status, and parasitized status). My first chapter indicates that reproductive physiology is sensitive to who is nearby (i.e., the opposite-sex social environment), while my second and third chapters suggest that aspects of mate preferences are sensitive to the traits of the individuals who are displaying the preferences. Thus, as a whole my dissertation demonstrates that behaviors deployed during mating and reproducing are variable and non-uniform within populations.