Epigenetics and adaptive evolution within the family environment

父母在许多方面影响后代的发展轨迹，而不仅仅是DNA的传递。在人类中，父母的生活史（例如，饮食）而不是遗传是各种可遗传健康风险发展的重要预测因子（例如，糖尿病、肥胖症）。此外，这些疾病的风险在几十年内增加了一个数量级。这些过程被认为反映了更大的适应性进化过程的一个小快照。事实上，父母的影响可能会对进化的时间尺度产生影响，缓冲或促进人口对快速环境变化的反应。然而，经典的遗传进化模型不能充分解释性状如何迅速适应和改变以应对不断变化的环境。一种理论解释是，家庭环境可以加速这些过程。然而，父母可能驱动适应性进化变化的生物学机制尚未阐明。我的项目将探索表观遗传机制可能介导这一过程的想法。表观遗传机制是生化标记和信号，最终决定DNA对细胞内因子的可及性，使其得以表达。我以前已经表明，这些表观遗传因素是由父母和社会家庭环境的变化引起的，可以从父母那里遗传给后代。我建议研究表观遗传机制是否也可以驱动自适应进化的变化，使用埋葬甲虫（Nicrophorus vespilloides）作为模型系统。这个物种有丰富而复杂的社会家庭生活，但寿命很短，在许多世代的过程中进行了严格的进化表观遗传学研究（例如，我的合作者利用埋葬甲虫在照顾方面的自然变化，在实验室中建立了两种类型的实验进化种群，它们只在幼虫发育期间经历的家庭环境中变化，并且在种群内为连续几代创造了相同的家庭环境。在完全护理人群（FC）中，父母在整个发育过程中一直与他们的年轻人在一起。相比之下，在无护理人群（NC）中，父母在他们的后代孵化之前被移除。这种操作表明，埋葬甲虫是高度响应家庭环境，去除护理诱导形态和行为的快速进化变化。例如，在NC下进化的幼虫变得对资源更具竞争力，并且相对于它们的身体尺寸发展更大的下颌骨;这些特征与几代幼虫存活率增加相关。我计划通过将表观遗传和遗传变异的分析与卵子中父母影响的详细分析相结合，研究表观遗传机制在驱动这些适应性进化变化中的作用。这项研究将首次通过实验确定表观遗传机制是否能够使家庭环境影响适应性进化变化。了解在不断变化的环境下遗传和表观遗传变化之间的相互作用以及这些系统所提供的灵活性程度，对于研究性状如何在几代之间遗传具有广泛的意义，并应用于行为生态学，保护，医学和流行病学领域。

Parents influence the developmental trajectories of their offspring in many ways beyond the transmission of DNA. In humans, parental life-histories (e.g., diet) and not genetics are significant predictors for the development of various heritable health risks (e.g., diabetes, obesity). Moreover, these disease risks have increased in frequency an order of magnitude within a few decades. These processes are thought to reflect a small snapshot of the larger adaptive evolutionary process. Indeed, parental effects may have consequences on an evolutionary time-scale, buffering or facilitating a population's response to rapid environmental change. Yet classical genetic models of evolution inadequately explain how rapidly traits adapt and change in response to changing environments. One theoretical explanation is that family environments can accelerate these processes. However, the biological mechanisms through which parents may drive adaptive evolutionary change has yet to be elucidated. My project will explore the idea that epigenetic mechanisms might be mediating this process. Epigenetic mechanisms are the biochemical marks and signals that ultimately determine how accessible DNA is to factors within the cell that allow it to be expressed. I have previously shown that these epigenetic factors are induced by changes in the parental and social family environment and can be inherited by offspring from their parents. I propose to examine whether epigenetic mechanisms can also drive adaptive evolutionary change using the burying beetle (Nicrophorus vespilloides) as a model system. This species has a rich and complex social family life but a short lifespan, making rigorous evolutionary epigenetic studies over the course of many generations (e.g., 25+) in this system tractable and feasible.My collaborators have exploited natural variation in care in the burying beetle to establish two types of experimentally evolving populations in the laboratory, which vary only in the family environment that larvae experience during development, and in which the same family environment is created for successive generations within populations. In Full Care populations (FC), parents remain with their young throughout development. In contrast, in No Care populations (NC), parents are removed just before their offspring hatch. This manipulation has revealed that burying beetles are highly responsive to the family environment, and removal of care induces rapid evolutionary change in morphology and behaviour. For example, larvae evolving under NC become more competitive for resources and develop larger mandibles relative to their body size; these traits are correlated with increased larval survival over generations. I plan to investigate the role of epigenetic mechanisms in driving these adaptive evolutionary changes by combining analyses of epigenetic and genetic variation with detailed analyses of parental effects in the egg. This study will be the first to experimentally determine whether epigenetic mechanisms enable the family environment to influence adaptive evolutionary change. Understanding the interaction between genetic and epigenetic change under changing environments and the degree of flexibility afforded by these systems has broad implications for the study of how traits become heritable between generations with applications for the fields of behavioural ecology, conservation, medicine and epidemiology.