Seascape genetics in the cold

了解种群如何通过基因流动联系在一起，对于预测它们可能如何应对未来的环境变化至关重要。然而，影响遗传连通性的因素仍然知之甚少，特别是在海洋领域，生命史等内在因素可能与洋流和海底拓扑等多种物理变量相互作用。探索这些因素如何导致遗传变异在海洋环境中被称为海景遗传学，对于了解海洋生物多样性将如何应对气候变化至关重要。该项目将建立在已经进行的广泛的先导研究的基础上，并利用现有的大量南极海洋软体动物南极洲马加拉样本，以阐明各种因素如何塑造扩散受限的海洋无脊椎动物的种群遗传结构。由于扩散主要是通过成虫的爬行进行的，海底拓扑结构和底物类型可能是种群结构的关键驱动因素，尽管附着在岩石和海藻上的卵块也可能通过洋流运输。我将使用一个空间上明确的建模框架来测试这些替代假设的支持，该框架包含了南极半岛西部128个地点的基因样本，南极半岛西部是地球上变暖最快的地区之一。由于每个因素的贡献可能取决于地理尺度，人口结构将在四个层次上进行评估：(A)沿半岛(宏观地理尺度)，(B)单一海湾(中地理尺度)，(C)三重100m x 200m网格(微观地理尺度)，以及(D)三重5m x 5m网格(纳米地理尺度)。总共2660个样本将通过与限制酶切点相关的DNA测序在大约25,000个SNP上进行基因分型。通过解决非常细微的遗传差异，这将使我们能够详细研究海流、地形和底物类型如何影响低至100万的尺度上种群结构的强度和模式。这些遗传数据还将使复杂的遗传分析成为可能，而此前对南极海洋生物的大多数研究都无法获得这些分析。例如，由于该物种容易受到冰川冲刷的影响，这一过程可能会极大地改变当地种群的人口结构，因此将模拟替代的历史人口情景，以检验瓶颈对种群结构有重大影响的假设。总体而言，通过将南极洲地区作为海景模型，该项目将对在多个空间尺度上塑造种群结构的机制产生前所未有的详细见解，对预测海洋生物在气候变化下的表现具有重要意义。

Understanding how populations are connected by gene flow is essential for predicting how they may respond to future environmental change. However, the factors affecting genetic connectivity are still poorly understood, particularly in the marine realm where intrinsic factors such as life history may interact with multiple physical variables like ocean currents and sea bed topology. Exploring how such factors cause genetic variation to be structured in marine environments has been termed seascape genetics and is crucial for understanding how marine biodiversity will respond to climate change.This project will build upon extensive pilot studies already conducted and exploit a large existing sample set of a brooding Antarctic marine mollusc Margarella antarctica to elucidate how various factors shape the population genetic structure of a dispersal-restricted marine invertebrate. As dispersal is primarily mediated by the crawling of adults, sea bed topology and substrate type are likely to be key drivers of population structure, although egg masses attached to rocks and seaweed might also conceivably be transported in ocean currents. I will test support for these alternative hypotheses using a spatially explicit modelling framework incorporating genetic samples from 128 locations on the Western Antarctic Peninsula, one of the fastest warming regions of the planet. As the contribution of each factor could conceivably depend on the geographic scale, population structure will be evaluated on four hierarchical levels: (a) along the peninsula (macro-geographic scale), (b) within a single bay (meso-geographic scale), (c) within triplicated 100m x 200m grids (micro-geographic scale), and (d) within triplicated 5m x 5m grids (nano-geographic scale).A total of 2660 samples will be genotyped at around 25,000 SNPs using restriction site associated DNA sequencing. By resolving even very subtle genetic differences, this will allow detailed investigation of how currents, topography and substrate type influence the strength and pattern of population structure over scales down to as little as 1m. The genetic data will also allow sophisticated genetic analyses that have been unavailable to most previous studies of Antarctic marine organisms. For example, as this species is susceptible to ice scouring, a process that could dramatically alter the demography of local populations, alternative historical demographic scenarios will be modeled to test the hypothesis that bottlenecks have a major affect on population structure..Overall, by using M. antarctica as a seascape model, this project will generate unprecedentedly detailed insights into the mechanisms that shape population structure over multiple spatial scales, with important implications for predicting how marine organisms will fare under climate change.