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一个主要目标，其中必须解决最终（进化，通常选择性）和最近（生理）的因果因素。一般认为，物种特异性的行为特征，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而来的。然而，个体之间可观察到的相互作用以及从这些相互作用中出现的社会结构，广泛地从遗传水平上移除，并且将基因与行为联系起来的生理机制没有得到充分的记录。从广义上讲，从可观察到遗传，涉及两组联系：第一，行为和生理学之间，第二，生理学和遗传之间。第一种方法已经引起了相当大的关注和努力，但第二种方法直到最近还很难获得，特别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”或其他非遗传传播进化的假设，尽管似乎是合理的，但仍然没有得到证实。该项目旨在区分影响生殖和应激激素个体差异的因素，并澄清遗传，内分泌生理学和社会行为之间的联系。作为这个方向的第一步，本研究将确定是否有显着比例的睾酮和糖皮质激素浓度的变化可以归因于遗传在一个大的，遗传多样性的，完全血统的圈养狒狒（狒狒hamadryas）来自几个亚种的人口。研究受试者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营养和其他外部因素的差异，替代笼养安排（单男性，多女性，全男性）部分模拟野生雄性狒狒之间的社会经验的变化。 将收集250只纯种成年雄性的粪便样本，并记录行为观察结果以确定优势等级。将从样本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。激素水平将被应用到系谱数据库中，以估计在各种社会和环境因素的背景下遗传的相对影响。社会内分泌学最近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。这项研究将是第一个同时调查在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，以跨学科的方法研究生理学和行为，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、生态学和进化提供了类比，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力具有意义。这个项目也可能有助于目前的研究调查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对生殖和应激激素浓度的个体差异的因素。

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.