Evolutionary responses to ocean acidification in free-living protists.

虽然许多严重的后果，影响生存在一个日益酸化的海洋已经吸引了很多关注，特别是，例如，对钙化生物的生理影响，我们还没有认识到长期的进化反应，这种选择压力及其伴随的影响种内生物多样性。这是我们知识中的一个关键空白，因为生物多样性在种群持续性中起着关键作用，从而影响生态系统功能。为了解决这个问题，我们提出了一个模型海洋原生生物的实验方法，因为这个分类群是快速增长，生态上的重要性，广泛，似是而非，并占据了一系列的环境。具体而言，我们选择了异养鞭毛虫Oxyrrhis marina，因为它是广泛的，易于培养，其生长速率受pH条件的影响，虽然具体的生理反应各不相同的菌株。利用一系列实验对来自世界各地海洋栖息地的多种（遗传和生理生态）O.marina文化进行研究，我们的目标是确定（1）海洋酸化对种内多样性和种群结构模式的未来后果，以及（2）确定未来气候情景是否有可预测的结果。具体来说，我们问：1。海水中的O. marina菌株对酸化反应的生理生态变化程度如何？2.从菌株的生理生态学特征可以预测跨越酸度梯度的进化结果吗？3.系统复杂性是否影响决定论的程度？4.酸化的速率是否影响了O.marina的适应能力，从而影响了进化的结果？我们首先分析了海洋O.marina分离株生长速率的生理生态变化谱，以建立它们在不同海洋酸度下竞争能力的预测模型。此外，将对菌株之间的遗传差异水平进行量化，并用于确定对pH值的响应是否具有明显的地理成分。接下来，我们研究的情况下，选择可能会更强，选择的响应更确定性/可预测性，酸度增加。因此，将回溯100-200代以上对pH具有不同生长响应的菌株之间的竞争结果，以揭示“随时间进化”的进展。将这些实验的数据与不同pH下生长速率的预测模型进行比较，从而确定对选择的反应是可预测的还是随机的。此外，我们目前的工作揭示了北大西洋（低多样性）和地中海（高多样性）之间生物多样性的二分法，这可能影响到该区域对环境变化的总体反应。为了确定遗传多样性（群体复杂性）是否影响选择结果，我们将在单一pH下进行另一项长期（100-200代）选择实验，其中重复群体具有不同水平的常设遗传变异。这个实验确定了菌株之间竞争的结果是否随种群多样性而变化，以及当有更大的遗传变异可供选择时，选择的反应是否更强。最后，我们假设快速变化将比缓慢变化产生更大的影响，这可能使菌株适应。因此，我们将在一系列驯化期内比较多达10种不同菌株的处理反应。这些实验将不仅揭示海洋酸化的直接影响，而且揭示这种公认的气候变化压力对海洋生命进化的潜在后果，从而揭示我们的海洋对不可避免的变化的适应性。

While many gross consequences that impact upon survival in an increasingly acidified ocean have attracted much attention, particularly, for example, the physiological effects upon calcifying organisms, we have yet to appreciate the long-term evolutionary response to this selective pressure and its concomitant effect on intraspecific biodiversity. This is a critical gap in our knowledge as biodiversity plays a key role in population persistence and thus affects ecosystem function. To address this issue, we propose an experimental approach on a model marine protist since this taxon is fast-growing, ecologically important, widespread, specious and occupies a range of environments. Specifically, we have selected the heterotrophic flagellate Oxyrrhis marina as it is widespread and easy to culture, and its growth rate is affected by pH conditions, although the specific physiological response varies among strains. Using a series of experiments on a bank of diverse (genetically and ecophysiologically) O.marina cultures sourced from habitats across the World's oceans, we aim to determine (1) the future consequences of ocean-acidification on patterns of intraspecific diversity and population structure and (2) identify whether there is a predictable outcome to future climate scenarios. Specifically we ask: 1. What is the extent of ecophysiological variation among O.marina-strains in response to acidification? 2. Is the outcome of evolution across an acidity gradient predictable from the ecophysiological profiles of strains? 3. Does system complexity affect the degree of determinism? 4. Does the rate of acidification affect the ability of O.marina to acclimate and thus impact on the outcome of evolution? We first characterise the spectrum of ecophysiological variation in growth rates in O.marina isolates to develop predictive models about their competitive ability under different ocean acidities. In addition, the level of genetic differences between strains will be quantified and used to determine whether response to pH has a distinct phylogeographic component. Next, we examine the scenario that selection is likely to be stronger, and the response to selection more deterministic/predictable, as acidity increases. Thus, the outcome of competition between strains with different growth responses to pH over 100-200 generations will be back-tracked to reveal the progress of 'evolution through time'. Data from these experiments will be compared to the predictive model of growth rates under different pHs, thus determining whether response to selection is predictable or stochastic. In addition, our current work reveals a dichotomy in biodiversity between the North Atlantic (low diversity) and the Mediterranean (high diversity) which may impact on the regions' overall response to environment change. To determine whether genetic diversity (population complexity) impacts upon the outcome of selection we will run another long-term (100-200 generation) selection experiment at a single pH with replicate populations founded with different levels of standing genetic variation. This experiment determines whether the outcome of competition between strains varies with population diversity, and whether the response to selection is stronger when there is greater standing genetic variation for select for selection to act upon. Finally we hypothesise that rapid changes will have greater impact than slow changes, which may allow strains to acclimate. Therefore, we will compare the responses of treatments of up to 10 divergent strains across a range of acclimation periods. Together these experiments will reveal not simply the immediate impact of ocean acidification but the potential consequences of this well accepted climate-change pressure on the evolution of life in the oceans, and thus the adaptability of our oceans to inevitable change.