Epigenetics and adaptive evolution within the family environment

父母在许多方面影响后代的发育轨迹，而不仅仅是DNA的传递。在人类中，父母的生活史（如饮食）而非基因是各种遗传性健康风险（如糖尿病、肥胖）发生的重要预测因素。此外，这些疾病风险的频率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，亲代效应可能在进化的时间尺度上产生影响，缓冲或促进种群对快速环境变化的反应。然而，经典的进化遗传模型并不能充分解释性状如何迅速适应和改变以响应不断变化的环境。一种理论解释是，家庭环境可以加速这些过程。然而，通过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，它最终决定了DNA对细胞内允许其表达的因子的接近程度。我之前已经证明，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，并且可以由后代从父母那里遗传。我建议以埋葬甲虫（Nicrophorus vespilloides）为模型系统，研究表观遗传机制是否也能驱动适应性进化变化。该物种具有丰富而复杂的社会家庭生活，但寿命较短，这使得在该系统中进行多代（例如25代以上）的严格进化表观遗传学研究变得容易和可行。我的合作者利用了埋甲虫的自然变化，在实验室中建立了两种实验进化的种群，它们只在幼虫在发育过程中经历的家庭环境中发生变化，并且在同一家庭环境中为种群内的连续几代创造了相同的家庭环境。在全照护群体（FC）中，父母在孩子的整个发育过程中一直陪伴着他们。相比之下，在无护理种群（NC）中，父母在后代孵化之前被移除。这种操作揭示了埋葬甲虫对家庭环境的高度反应，并且去除照顾会导致形态和行为的快速进化变化。例如，在NC条件下进化的幼虫对资源的竞争更激烈，并且相对于它们的体型发育出更大的下颌骨；这些特征与几代幼虫的存活率增加有关。我计划通过结合对表观遗传和遗传变异的分析，以及对亲本对卵子的影响的详细分析，来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，对研究性状如何在代际间遗传具有广泛的意义，并在行为生态学、环境保护、医学和流行病学等领域具有应用价值。

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.