Doctoral Dissertation Research: Factors Influencing Steroid Hormone Variation in Male Baboons

解释相关类群之间社会行为的一致差异是比较社会生态学的主要目标，其中必须解决最终（进化的，通常是选择性的）和近因（生理的）原因。一般来说，合理的假设是，物种特有的行为特征，就像表型的其他诊断方面一样，具有独特的遗传基础，主要是在自然选择的影响下进化的。然而，可观察到的个体之间的相互作用以及从这些相互作用中产生的社会结构在遗传水平上被广泛地移除，并且将基因与行为联系起来的生理机制也没有充分的文献记录。从广义上讲，从可观察到遗传，涉及两组联系：第一，行为和生理之间的联系；第二，生理和遗传之间的联系。前者已经引起了相当多的关注和努力，但后者直到最近才变得更加难以接近，尤其是在灵长类动物和其他社会复杂的动物中。只要是这样，行为多样性是通过自然选择而不是通过“传统”或其他非遗传遗传而进化的假设，尽管似乎是合理的，但仍然没有得到证实。本项目旨在区分影响生殖激素和应激激素个体差异的因素，阐明遗传、内分泌生理和社会行为之间的联系。作为这个方向的第一步，本研究将确定睾丸激素和糖皮质激素浓度变化的显著比例是否可归因于遗传，遗传多样性，来自几个亚种的完全纯种圈养狒狒（Papio hamadryas）种群。研究对象被安置在德克萨斯州圣安东尼奥的西南生物医学研究基金会。虽然圈养条件最大限度地减少了营养和其他外部因素的差异，但其他笼子安排（单雄性，多雌性，全雄性）部分模拟了野生雄性狒狒之间社会经验的变化。将收集250只纯种成年公犬的粪便样本，并记录行为观察以确定优势等级。将从样品中提取睾酮和糖皮质激素，并通过放射免疫测定法测量激素浓度。激素水平将应用于谱系数据库，以估计遗传对各种社会和环境因素背景的相对影响。最近社会内分泌学的主要进展集中在环境因素、激素和行为之间的相互作用。该项目将通过关注遗传因素在相互作用中的可能作用来补充这项工作。这项研究将首次同时研究受控环境条件下类固醇激素（睾酮和糖皮质激素）浓度个体差异的遗传和非遗传来源。该研究将整合遗传、内分泌和行为数据，以跨学科的方式研究生理学和行为，通过合并定量遗传学、社会内分泌学和行为生物学领域，促进学术和生物医学机构的合作。由于狒狒为人类的发育、生态和进化提供了类比，因此这项研究对遗传因素对生理变异的影响以及人类和其他灵长类动物行为进化的潜在影响具有启示意义。该项目也可能有助于目前研究睾酮和糖皮质激素在人类男性发育、健康和疾病中的作用，也许指导未来的公共卫生研究，以了解生殖和应激激素浓度的个体差异。

Explaining consistent differences in social behavior between related taxa is a major goal of comparative socioecology, in which both ultimate (evolutionary, generally selective) and proximate (physiological) causal factors must be addressed. It is generally, and reasonably, assumed that species-specific behavioral traits, like other diagnostic aspects of phenotype, have distinctive genetic underpinnings that have evolved, mainly under the influence of natural selection. Observable interactions among individuals and the social structures that emerge from those interactions are, however, widely removed from the genetic level, and the physiological mechanisms linking genes to behavior are inadequately documented. Broadly speaking, in tracing back from the observable to the inherited, two sets of links are involved: first, between behavior and physiology and second, between physiology and heritage. The first has attracted considerable attention and effort, but the second has until recently been much less accessible, especially in primates and other socially complex animals. As long as this is so, the hypothesis that behavioral diversity has evolved by natural selection, rather than by "tradition" or other non-genetic transmission, though plausible, remains unproven. This project aims to differentiate factors that influence individual variation in reproductive and stress hormones and clarify the connection between heritage, endocrine physiology and social behavior. As a first step in this direction, this study will determine whether a significant proportion of variation in concentration of testosterone and glucocorticoids can be attributed to heritage in a large, genetically diverse, and fully pedigreed population of captive baboons (Papio hamadryas) derived from several subspecies. Study subjects are housed at the Southwest Foundation for Biomedical Research in San Antonio, TX. While captive conditions minimize variance in nutrition and other external factors, alternative caging arrangements (single-male, multi-female; all-male) partially simulate variation in social experience among male baboons in the wild. Fecal samples from 250 pedigreed, adult males will be collected and behavioral observations will be recorded to determine dominance rank. Testosterone and glucocorticoids will be extracted from the samples and measured for hormone concentration by radioimmunoassay. Hormone levels will be applied to the pedigree database to estimate the relative impact of heritage against a background of various social and environmental factors.Recent major advances in socioendocrinology have concentrated on interactions between environmental factors, hormones, and behavior. This project will complement this work by focusing on the possible role of genetic factors in the interaction. This study will be the first to simultaneously investigate the genetic and non-genetic sources of individual differences in the concentration of steroid hormones (testosterone and glucocorticoids) under controlled environmental conditions. The research will integrate genetic, endocrine, and behavioral data in an interdisciplinary approach to the study of physiology and behavior fostering collaboration of academic and biomedical institutions by merging fields of quantitative genetics, socioendocrinology, and behavioral biology. Since baboons have provided analogies for human development, ecology, and evolution, this study has implications for the effects of genetic factors on physiological variability, and hence the potential for behavioral evolution, in humans and other primates. This project may also contribute to current research investigating the role of testosterone and glucocorticoids in human male development, health, and disease, perhaps directing future public health research toward factors underlying individual differences in reproductive and stress hormone concentration.