Impacts of Southern Ocean warming on marine connectivity: Integrating oceanographic modelling with molecular ecology and developmental biology

摘要：我们的工作汇集了鱼类幼体发育率、种群遗传学、海洋环流和环境(特别是温度)的数据，以产生可以检验的补充预测。这为我们提供了一个强大的工具，来解决在一个快速变化的世界中野生种群动态的不确定性。许多鱼类种群与生活在自然界的所有物种一样，暴露在环境的各种变化中，这些变化决定了它们的丰度和分布。有些变化是自然的，包括食物供应或配偶数量的变化，而另一些变化主要是由人为活动驱动的，其中气候变化和剥削是两大类型。由于鱼类是自然生态系统的主要组成部分，为许多其他动物提供食物，是许多种群的捕食者，而且它们也是全球人类食物的主要来源，因此我们必须估计各种环境变化对其动态的作用，特别是考虑到许多鱼类种群最近已经崩溃，或仅处于恢复的早期阶段。在这里，我们使用南极一个有特色的地区的几种鱼类，研究温度上升可能对进入成年种群的鱼类数量(“补充”)的潜在影响，更具体地说，是它们幼体的发育速度。众所周知，在较高的温度下，依赖蛋黄资源获取营养的幼虫在较高的温度下会更快地耗尽这些供应，这意味着它们可能无法及时到达合适的摄食地发育成鱼。在这种情况下，较少的年轻人将被招募到下一代个体中，由于在地点之间的分散将减少，预计种群将失去连接，这对种群和生态系统的弹性产生后续影响。我们将通过观察几种在生活史上略有不同的鱼类幼虫的特征，并比较它们的发育速度与温度波动的关系，来检验这种影响的可能性有多大。我们通过两种方法测试较高的温度是否确实导致更快的发育：(1)用一个季节内适应不同温度制度的活幼虫，(2)用从野外采集的多年发育温度制度不同的存档幼虫标本。然后，我们将这些信息添加到基于个体的模型中，该模型结合了海洋环流和每个物种的生物特征，从而创建了特定物种的生物物理模型。这使我们能够测试发育速度的任何变化是否会影响幼虫到达适当的摄食地并招募到成年种群的可能性。目前扩散的模型预测将通过与遗传分析推断的扩散进行比较来验证，对海洋年际变化造成的扩散变异性的评估将使人们能够将气温上升的影响放在一起考虑。然后，就可以预测该地区预计的气温上升对作为气候变化组成部分的鱼类补充的可能影响。这样的信息很重要，因为南极的气候记录显示，南极水域的变暖速度比全球海洋整体变暖的速度更快。这不仅对南极独有的许多生物多样性具有重要意义，而且众所周知，南大洋影响着全球气候。最终，我们将来自大自然的与环境相关的数据与经过基因验证的“生物物理”模型相结合，将能够更真实地预测海洋变暖对海洋物种和生态系统的影响。

General Summary: Our work brings together data on developmental rate of fish larvae, population genetics, ocean circulation and the environment (specifically temperature) to generate predictions of recruitment that can be tested. This provides us with a powerful tool for tackling the uncertainty that characterizes the dynamics of wild populations in a rapidly changing world. Many fish populations, as all species living in nature, are exposed to a wide variety of changes in the environment that determine their abundance and distribution. Some changes are natural and include such things as alterations in food supply or number of mates, while others are largely driven by man-made activities, of which climate change and exploitation are two major types. Since fish form a major component of natural ecosystems in providing food for many other animals, and are predators of many groups, and since they also form a major source of human food globally, it is important that we estimate the role of various environmental changes on their dynamics, especially as many fish populations have recently collapsed, or are only in early stages of recovery. Here we examine, using several fish species from a well characterised region of the Antarctic, the potential effect that an increase in temperature might have on the numbers of fish entering the adult population ('recruitment'), and more specifically the rate at which their larvae develop. It is well established that at higher temperatures, larvae that rely on yolk resources for nutrition will exhaust these supplies more quickly at higher temperatures, meaning they may not reach appropriate feeding grounds in time to develop into adults. In such circumstances, fewer young will recruit to the next generation of individuals, and since dispersal among sites will be reduced, populations would be expected to lose connectivity, which has follow-on effects on population and ecosystem resilience. We will examine how likely such effects are by observing fish larvae of several species differing slightly in their life history larval characteristics, and compare their rates of development in relation to fluctuations in temperature. We test whether higher temperatures do indeed lead to faster development by two means: (1) with live larvae acclimated to different temperatures regimes within a season, and (2) with archived larval specimens sampled from the wild across multiple years in which developmental temperature regimes varied. We then take this information and add it to Individual Based Models incorporating ocean circulation and biological characteristics of each species, thus creating species-specific biophysical models. This allows us to test whether any changes in rate of development will influence the likelihood of larvae reaching appropriate feeding grounds and recruiting to the adult population. Model predictions of dispersal for the present-day will be validated by comparison with inferred dispersal from genetic analyses, and an assessment of dispersal variability due to interannual oceanographic variability will allow the effects of increased temperature to be placed in context. It will then be possible to make predictions about the likely effects of the predicted increases in temperature in the area on fish recruitment as a component of climate change. Such information is important since climate records from the Antarctic show that the waters of the Antarctic are warming more rapidly than the global ocean as a whole. Not only is this significant for much of the biodiversity that is unique to the Antarctic, but the Southern Ocean is known to influence climates globally. Ultimately, our integration of environmentally relevant data taken from nature, with genetically validated 'biophysical' models will enable a more realistic projection of the impact of ocean warming on marine species and ecosystems.