ABSTRACT Proposal: #96-23546 PI: Crews & Rhen Title: Evolutionary origin of behavioral organization Organization of reproductive and aggressive behaviors by estradiol (via aromatization of testosterone in mammals) during early development is well documented in birds and mammals. There is a correlation between the organized and heterogametic sex in these groups; males are organized (lose the ability to display female-typical behavior) in mammals, whereas females are organized (lose the ability to display male-typical behavior) in birds. The opposite sex retains the capacity to display both female- and male-typical behavior. A similar correlation is observed in other vertebrates with genotypic sex determination. Alternate explanations are (1) that a developmental constraint results in organization of the heterogametic sex, or (2) that there is a functional relationship between organization and gonochorism. Reptiles with environmental sex determination do not fit into the constraint paradigm because they lack a heterogametic sex. In contrast, these species may be organized if organization is adaptive. In this study, manipulation of embryonic temperature (and thereby gonadal sex) and adult hormones will be performed to distinguish among hypotheses about organization. Log-linear, multivariate, and path analyses will be used to analyze reproductive and aggressive behaviors. Results will (1) illuminate the proximate cause of behavioral variation in an ESD species, and (2) for the first time delineate and test alternate hypotheses about the evolutionary causes of behavioral organization in the context of sex determining mechanisms.
