Hubert Schwabl, Ph.D. - US grants

ethology; neuroendocrine system; hormone regulation /control mechanism; brain; environmental adaptation; phenotype; stress; sex hormones; sex behavior; hippocampus; corticosteroids; glucocorticoids; evolution; steroid hormone; vocalization; corticosteroid receptors; memory; learning; behavior test; Aves; blood chemistry;

In many socially monogamous bird species, males sometimes engage in extra-pair copulations and sire viable offspring. Conventional wisdom has been that all males are continuously ready for such opportunities, but recent field studies of reproductive hormones have shown that testosterone (T) fluctuates greatly during the nesting cycle, peaking early during courtship/mating, then plummeting in tandem with a dramatic behavioral switch to care-giving activities (incubating and feeding nestlings). It has been proposed that males may experience reduced interest in or capacity for extra-pair matings when T is low, that they may then experience a physiological 'time-out' phase of their cycle. To test this, one sample of male house sparrows will be given time-release hormone implants (keeping T-levels high), while another sample serves as normal (cycling) controls. The resulting patterns of extra-pair paternity, as revealed by DNA fingerprinting, will allow assessment of what a male sacrifices by cycling. Conversely, the quality of parental care received by the nestlings of implanted vs. control males will show what is gained from cycling. Parallel experiments will calibrate the mechanism(s) responsible.

This project will improve understanding of the social forces that promote and maintain monogamy, a relatively rare mating system in nature. It focuses attention on the costs and benefits available to males for investing heavily in one primary brood by evaluating the factors that constrain the pursuit of alternative mating partners.

This Integrative Graduate Education and Research Traineeship (IGERT) award establishes a novel Ph.D. training program designed to bridge the gap between anthropology and biology. The program provides students in both fields a common curriculum that emphasizes evolutionary processes of adaptation and diversification in genetic, behavioral, and cultural domains. Students will become adept in state-of-the-art methods including computational modeling, game theory and phylogenetic analysis that are applicable to study of evolutionary processes across these domains. Students enter the program through the Department of Anthropology or the School of Biological Sciences at Washington State University, Pullman, or through the Department of Anthropology at the University of Washington, Seattle. They spend at least one term taking courses or pursuing research at the sister institution, and form research teams across these universities and disciplines, allowing them to draw on relevant expertise in either sponsoring university. In addition they have the opportunity to pursue research at a domestic partner, the Santa Fe Institute in New Mexico, and at three international partners: the Centre for the Evolution of Cultural Diversity, University College London; Le Centre Universitaire de Recherche et de Documentation en Histoire et Archologie, Central African Republic; and the University of Costa Rica. The program aims to educate professionals versed in evolutionary approaches integrating the study of biology and culture, familiar with the most important perspectives and quantitative techniques for studying culture change and the evolution of social behavior in both humans and non-humans. Outreach to area schools and local native American groups is planned to strengthen the teaching of evolution in K-12 schools and to increase the breadth of approaches for understanding evolution. IGERT is an NSF-wide program intended to meet the challenges of educating U.S. Ph.D. scientists and engineers with the interdisciplinary background, deep knowledge in a chosen discipline, and the technical, professional, and personal skills needed for the career demands of the future. The program is intended to catalyze a cultural change in graduate education by establishing innovative new models for graduate education and training in a fertile environment for collaborative research that transcends traditional disciplinary boundaries.

Most (~75%) vertebrate species of the world inhabit tropical and southern hemisphere regions, and are generally characterized with a 'slow' development rate. North temperate species, in contrast, generally posses a 'fast' development rate. This project will combine controlled comparative analyses with manipulative experiments to examine whether epigenetic maternal effects, mediated by maternal hormones, are proximate mechanisms causing the variation of development rate and related life history strategies across latitudes. It explores and experimentally tests the hypotheses that variation in exposure of the avian embryo to maternally derived hormones in the egg explains variation in offspring development rate. Maternal hormones selected for study are: i) androgens because they show strong correlations with development rate in temperate zone passerines; and ii) thyroid hormones because they are regulators of vertebrate development and metabolism. The hypothesis predicts these egg hormones i) to be lower in tropical than temperate passerines; ii) to cause variation in rate of embryo development; iii) to cause trade-offs between development rate and offspring quality such as immune function, thereby explaining variation in other life history traits as well. Proposed studies will be conducted in conjunction with ongoing long-term investigations conducted by Dr. Thomas Martin (U. Montana) that address the ultimate causes (e.g. offspring and parent mortality) of variation in development rate in the same model systems with a tight integration of projects and approaches. This will provide a powerful and unique tool for testing hypotheses of evolution of life histories, generating novel and critical insights into epigenetic maternal effects on life history evolution and evaluating selection pressures driving evolution of proximate mechanisms of maternal effects in both the parent (reproductive physiology) and the offspring (developmental physiology) generations. The project provides training of graduate and undergraduate students in integrative approaches to, and analyses of, complex biological questions.

Male animals typically show considerable plasticity in the behavioral tactics and signals that they use to obtain mates. For example, in many bird populations, some males breed in bright plumage while others breed in relatively dull plumage. It is generally thought that plastic expression of sexual traits depends on both intrinsic (body condition) and extrinsic cues (social interactions), allowing males to adjust their investment in signals according to their quality and relative likelihood of mating success, and consequently that such traits honestly signal male quality to conspecifics. However, the mechanisms that translate these cues to male sexual traits, and thereby allow for plastic expression of sexual traits, are poorly understood. This research will examine the mechanisms of flexible expression of male reproductive phenotypes in the red-backed fairy wren (Malurus melanocephalus). In particular, this project will determine experimentally the effects of physical condition, social environment and stress on the hormones that affect male reproductive type. This work will combine both functional and mechanistic analyses, and will push the study of phenotypic plasticity and sexual signals in new directions. In addition, the research will explore carry-over effects of early life environment on male condition and reproductive type, a cutting-edge field of research emerging from the recent acknowledgement that early development can have important effects on adult traits. These results will have major implications for theoretical models of the evolution of sexual signals. This research also will contribute directly to the training of two graduate students and numerous undergraduates. Undergraduate training will include a novel internship program that will pair students from American universities with Australian students to conduct collaborative research. Thus, this project will involve undergraduates in all aspects of the research experience, from project design through publication, as well as giving them an enriching international experience.

Animals must adjust their behaviors and other traits to a constantly changing social environment. For example, the strategies and the signals that individuals use to attract mates and breed often depend on an individual's social status relative to others in the population, and that status can fluctuate as group composition changes and/or other individuals change in rank. Accordingly, the hormonal and genetic mechanisms that underlie such behaviors and signals are likely to be sensitive to social conditions. Yet, we know relatively little about these mechanisms, particularly in wild populations living under natural conditions. This project will examine the mechanisms that allow for behavioral flexibility, and the ways that those mechanisms evolve, using Australian fairy-wrens (genus Malurus) as a model system. These study species are uniquely suited to this research because they show pronounced variation, across both individuals and populations, in the visual signals that individuals use to attract mates, and a great deal is known about the effects of hormones (particularly androgens like testosterone) on the development of these signals. This project will use a state-of-the-art semi-automated radio tracking system to continuously monitor social interactions among individuals to examine the effects of those interactions on hormones and gene expression in the brain, and use experimental manipulation of social conditions in the field to demonstrate the underlying causes. Comparisons across populations and across the sexes will be conducted, making this one of the first studies to examine the role and regulation of breeding signals in females. Overall, this research will contribute to a better understanding of the hormonal and genetic mechanisms that allow individuals to adjust to a constantly changing social environment. In addition this work will build capacity in Papua New Guinea, a richly biodiverse region of considerable conservation concern, through key partnerships and direct involvement of locals in research, educational outreach, and interchange activities. Public educational materials also will be created, including short videos presenting results from the research as well as the process of doing the research, for broad dissemination through proven and highly visited internet channels. Thus, this project will have broad impacts on both conservation and public understanding of science.

A central goal of the animal behavior research agenda is to identify the role of androgens and other hormones in regulating expression of ornaments and associated reproductive behaviors, yet to date these roles remain unclear. One view, which has received relatively little attention from behavioral ecologists, is that androgens are phenotypic integrators that act to produce an adaptive multi-dimensional phenotype that is well suited to its social environment. This collaborative project will build on previous research with two sister species of Malurus fairy-wren that exhibit intraspecific variation in male and female ornamentation, making this system uniquely suited for examining these issues. The project consists of three inter-related studies that, together and synergistically, will address key questions regarding how androgens modulate expression of breeding signals and associated behaviors. First, high-density data on social interactions, collected from an automated telemetry array in conjunction with experimental manipulation of social environment, will be used to examine the role of social interactions and early-life conditions in regulating individual androgen levels and breeding phenotype. Second, a combination of observational, genomic and hormone manipulation approaches will be used to examine the extent to which androgens affect whole suites of characters to produce an integrated reproductive phenotype. Finally, hormone implant experiments and genomic analyses across the sexes and across two closely related species will reveal the degree of evolutionary constraint on hormonal mechanisms regulating ornament elaboration and behavior. By bridging the gap between the ways that behavioral ecologists and endocrinologists view hormones, this project will transform the ways that we view the role of hormones in regulating phenotypic integration and signaling.