LIMITS TO ADAPTATION: CAUSES, AND CONSEQUENCES FOR ECOLOGY AND ECOSYSTEM FUNCTION

物种正日益面临着应对人类干扰或气候变化引起的环境变化的挑战。它们是否能够应对气候变化，对生物多样性和我们从生态系统中获得的好处至关重要。如果我们要预测物种将如何应对不断变化的环境或帮助减轻气候变化的影响，物种进化和适应新环境条件的能力是我们需要了解的一个关键因素。了解物种适应的速度有多快，进化的限制是什么，以及一个物种的进化将如何影响与其相互作用的生态系统的其余部分，这一点尤为重要。在这个项目中，我们将通过一系列大型实验来调查这些问题，实验对象是一种名为水蚤的小型甲壳类动物，水蚤对水质和淡水生态系统的健康有重大影响。我们的方法有几个独特的优势。首先，水蚤可以克隆繁殖，这意味着我们可以操纵种群的遗传多样性，以检查其对适应速度和限制的影响。其次，我们将使用一个大型室外加热水箱系统——这是欧洲最大的此类设施——来检查水蚤及其相关生态系统对热浪的反应，这是物种面临的一个关键环境挑战。第三，我们将利用最新的DNA测序技术——可在利物浦的一个主要基因组学中心获得——来检查适应气候变化的遗传机制。最后，我们的研究得到了我们实验室最近令人兴奋的发现的支持，我们已经证明了两个过程——可塑性和表观遗传学——对适应的潜在重要性。可塑性允许个体根据环境改变其发育、生长和/或繁殖模式，而表观遗传学允许这些变化通过改变基因的作用传递给他们的后代。这些过程对于什么限制了动物适应环境变化的能力这一问题至关重要，因为它们可以使动物适应的速度远远快于传统的进化方式，而传统的进化方式只有基因的频率随时间而变化。因此，这些过程也可能有助于保护动物种群在环境变化后免于灭绝，从而使物种有时间在更长的时间内进化。该研究将：i)量化对动物的两大影响（食物和温度差异）如何影响水蚤生命的许多不同和关键方面（表型可塑性）；ii)利用这种可塑性的知识，以及水蚤是否适应当地或不同的环境，了解可塑性、遗传多样性和表观遗传学如何决定种群的进化潜力；Iii)了解种群进化潜力的限制将如何改变群落中其他物种的命运和整个生态系统的功能（例如通过调节水质和有害藻类的繁殖）。因此，这项研究将从根本上推进我们对以下方面的理解：三种不同的影响（遗传多样性、可塑性和表观遗传学）如何促进和结合，使种群能够适应环境变化，以及这如何影响其他物种，并最终影响淡水生态系统及其生物多样性提供的服务（清洁水、食物、纤维、舒适设施）。我们的研究结果将向学术界、政策制定者、学校和公众公布。

Species are increasingly faced with the challenge of coping with a changing environment caused by human disturbance or climate change. Whether they are able to cope or not is critical for biodiversity and the benefits that we get from ecosystems. The ability of species to evolve and adapt to new environmental conditions is a key factor that we need to understand if we are to predict how species will cope with a changing environment or to help mitigate the impacts of climate change. It is particularly important to understand how rapidly species can adapt, what the limits are to evolution, and how evolution of one species will affect the rest of the ecosystem with which it interacts.In this project, we will investigate these questions through a series of large scale experiments using a small crustacean called Daphnia, which has a major impact on water quality and the health of freshwater ecosystems. Our approach has several unique strengths. First, Daphnia can reproduce clonally, which means that we can manipulate the genetic diversity of populations to examine its effects on the rate and limits of adaptation. Second, we will use a system of large outdoor heated tanks - the largest such facility in Europe - to examine the response of Daphnia, and its associated ecosystem, to heat-waves, which is a key environmental challenge faced by species. Third, we will exploit the latest DNA sequencing technologies - available at a major genomics centre at Liverpool - to examine the genetic mechanisms underlying adaptation to climate change. Finally, our study is supported by recent, exciting findings from our laboratory where we have demonstrated the potential importance of two processes - plasticity and epigenetics - for adaptation. Plasticity allows individuals to change their pattern of development, growth and/or reproduction in response to the environment, and epigenetics allows these changes to be transmitted to their offspring by modifying the action of genes. These processes are central to questions about what limits the ability to adapt to environmental change, since they could allow the animals to adapt far more rapidly than they would by conventional evolution alone, in which only frequencies of genes change over time. As such, these processes may also help protect the animal populations from going extinct following an environmental change, so allowing time for the species to evolve over a longer period.The research will: i) quantify how two major influences on animals (food and temperature differences) affect many different and crucial aspects of the lives of Daphnia (phenotypic plasticity); ii) use the knowledge of this plasticity together with whether the Daphnia are adapted to local or different environments, to undertand how plasticity, genetic diversity and epigenetics determine the potential of populations to evolve; iii) understand how limitations in the potential of populations to evolve will alter the fate of other species in the community and the functioning of the whole ecosystem (e.g. by regulating water quality and blooms of harmful algae).This research will, therefore, fundamentally advance our understanding of how three different influences (genetic diversity, plasticity and epigenetics) contribute and combine to allow populations to adapt to environmental change, and how this can affect other species and ultimately the services (clean water, food, fibre, amenity) that freshwater ecosystems and their biodiversity provide. Our findings will be disseminated to the academic community, to policy-makers, to schools and to the general public.