• Parental Effects on Development
• Roles of Hormones in the Development and Maintenance of Sex-specific Reproductive Physiology and Behavior
• Disease, Immunity, and Reproductive Function

Recent literature and popular news stories reveal strong scientific and popular interest in the reproductive behavior of humans and other animals, including the myriad environmental influences on reproductive development.  Both genetic sex and the developmental environment are important sources of variation in the behavior, physiology, and morphology of males and females. Understanding the sexual phenotype – or gender – has far reaching implications for human health and well being.  An overriding objective of this training program is to enhance understanding of the genesis and relevance of sex and gender.

Long history has shown that important insights into the basic mechanisms of reproduction and development can be gained by study of non-human model systems as well as evolutionarily diverse non-model systems.  Further, recent history indicates that future progress in understanding the organism as more than the sum of its parts will require a synthesis of systems and molecular biology, in other words a multi-disciplinary approach.

The Program’s title, “Common Themes in Reproductive Diversity” is intended to focus attention on the universal challenge all animals must meet, to reproduce and provide for offspring, while also addressing the myriad ways in which animals accomplish these ends.  Training will be focused in 3 areas:  Parental Effects on Development; Roles of Hormones in the Development and Maintenance of Sex-specific Reproductive Physiology and Behavior; and Disease, Immunity, and Reproductive Function.

Parental Effects on Development. (top)

Mothers and fathers affect offspring development in countless ways, many non-genetic.  As just a few examples, maternal diet during egg production is known to affect offspring sex ratio, body size, and attractiveness to the opposite sex.   At the ecological level, population density influences maternal steroid levels, and thus yolk levels of steroids, which in turn influence offspring behavior.  Similarly, drugs applied during gestation can affect later sexual development in offspring.  And diseases experienced by mothers allow the transmission of protective antibodies to young. Because of the wide range of these effects, from the cell and molecular to frequency-dependent population effects, deep understanding will require concerted study using tools of numerous disciplines.

Several Program Faculty are devoted to research on parental effects.  Alberts studies the parent-offspring unit from the perspective of behavioral development, while Sengelaub studies the impact of maternal behavior on neural development of pups. Moczek studies how offspring development in beetles can be mediated by maternally controlled access to resources, while Ketterson addresses related questions in birds. Novotny and Sanders study sexual development from widely different chemical perspectives.  Strome explores the molecular genetic basis of sex determination, while Wade has addressed the evolutionary relationship between offspring sex ratio and variance in adult reproductive success.  In combination these faculty offer the means to synthesize the mechanisms and functional considerations that shape the parent-offspring unit and account for individual variation in behavior, particularly in relation to sex, gender and reproduction.

Roles of Hormones in the Development and Maintenance of Sex-specific Reproductive Physiology and Behavior. (top)

Across species, including humans, many of the behaviors, morphologies, and physiological processes that are essential for reproduction are sexually dimorphic.  Sex differences in physiology and behavior are often regulated by hormones, particularly gonadal steroid hormones, and investigation of the role of hormones and other biological and environmental factors in sexual differentiation is essential for understanding the normal development and adult expression of sex-specific traits in humans, as well as the effects of perturbations of the hormonal milieu on typical sexual development (e.g. intersex syndromes).  

Experiments on model and non-traditional organisms provide important insights into the shared mechanisms by which hormones guide sexual differentiation and/or influence adult reproductive physiology and behavior.  A number of Program Faculty whose expertise runs from the molecular to the evolutionary conduct research in these areas.  Taking a molecular approach are Cherbas, Moczek, Quirk and Strome, all of whom study the genetics and molecular biology of hormone actions during development.  A second set of faculty includes Smith and Sengelaub who address how hormones affect cellular physiology and anatomy so as to induce sexually dimorphic physiology and behavior at the level of the organism.  Members of a third sub-group consisting of Demas, Heiman, Ketterson, Novotny, Sanders, Sengelaub, Suthers, and Smith, all study the roles of hormones in mediating developmental and adult plasticity in reproductive behavior, including that of humans. Finally, several Program Faculty, Ketterson, Martins, Moczek, Suthers, and Smith, employ a comparative approach to the evolution of hormone-mediated sexual dimorphism.  Collectively the systems, techniques, and perspectives offered by these diverse scientists will provide students a unique opportunity to explore common themes in the role of hormones in accounting for reproductive diversity.

Disease, Immunity, and Reproductive Function. (top)

Sexual physiology and behavior are linked in a wide variety of intriguing ways with the transmission of diseases and parasites and an organism's ability to cope with disease and illness.  Not only is sexual behavior a major mode of disease transmission in humans as well as other animals, but many organisms make critical physiological trade-offs in allocating resources to the immune vs. the reproductive systems.  Furthermore, both sexually transmitted and non-sexually transmitted diseases and parasites play a critical role in the evolution and maintenance of sexual reproduction in natural populations. 

The program’s faculty includes leading experts in the relationships among disease, parasitism, immunity, and sexual reproduction.  Lively, for example, studies the role of disease and parasitism in the evolution and maintenance of sexual reproduction, Demas and Ketterson study tradeoffs between the immune system's ability to fight disease and reproductive physiology.  Wade studies how disease resistance evolves in structured populations, and Sanders and Heiman add expertise in human reproduction and the epidemiology of sexually transmitted diseases.