EFFECTIVE POPULATION SIZE AND CONNECTIVITY IN FISH

鱼类的有效种群规模和连通性

• 批准号: RGPIN-2014-04696
• 负责人: Ruzzante, Daniel
• 金额: $ 3.06万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=587961
• 关键词: EFFECTIVE; POPULATION; SIZE; CONNECTIVITY; FISH

A fundamental question in evolutionary and conservation biology is how habitat fragmentation influences the distribution of genetic diversity among populations and the ability of populations to adapt to local conditions. In my research, I use effective population size (Ne) as a measure of the genetic diversity of populations, and examine the mechanisms that determine the Ne of populations of fish found in complex landscapes. Effective population size is of importance to species conservation through its links to population persistence and evolutionary potential. Most species occur naturally as networks of populations interconnected by varying degrees of gene flow (meta-populations). Patterns of genetic diversity are thus a product of mechanisms that influence local population Ne’s (stochastic loss, local adaptive selection, gene flow), and the effective size of the meta-population (meta-Ne). Gene flow tends to increase Ne of local populations by countering the stochastic loss of genetic diversity, while directional selection is likely to reduce diversity. For meta-populations, theory predicts that the meta-Ne of a fragmented system will be smaller than that of a similar-sized panmictic system, if local populations contribute unevenly to the next generation. In complex, hierarchically arranged dendritic environments, however, the predicted meta- Ne can be greater than the sum of the local Ne’s. Dendritic watersheds, for example, have a hierarchical arrangement of local populations that usually leads to asymmetrical gene flow. Meta-Ne can also be affected by the environmental variation in the landscape that subjects populations to different selective pressures. My long term goals are to elucidate the genomic basis of local adaptation in fish within spatially complex meta-population systems, and to determine how gene flow and its asymmetries affect patterns of neutral and adaptive genetic diversity. I will be examining systems in several temperate post-glacial landscapes (Nova Scotia, Newfoundland, Labrador and Patagonia) that contrast in level of fragmentation and connectivity. These dendritic drainages differ in size and complexity, and thus are likely to differ in the relative importance of asymmetric gene flow and adaptive processes. I will also compare patterns of genetic diversity for sympatric species with very different life history traits in landscapes that contain lakes with contrasting selection pressures (water pH, transparency, productivity). The goal will be to disentangle the effects of gene flow, adaptive processes and species life histories on local Ne’s and meta-Ne. Some of this work will take place in the West River Sheet Harbour drainage in Nova Scotia, a highly complex dendritic system of nearly 20 interconnected lakes differing in environmental variables and containing three abundant sympatric species that vary in some key life history traits: banded killifish, yellow perch, and white sucker. My ongoing research addressing similar and related questions in salmonid species will continue focusing on the upper Humber river system in Newfoundland, while in Patagonia I will examine patterns of colonization and adaptation to salinity in the widespread Galaxias maculatus. At the other end of the connectivity spectrum I also work with marine species, including Atlantic herring, a highly abundant and widespread pelagic fish. This body of research will constitute some of the first empirical tests of the theoretical predictions regarding the effects of connectivity on the relationship between local population Ne’s and meta-Ne, and should give us some idea of the usefulness of the theory for understanding real systems as well help to indicate directions for further theoretical development.

进化和保护生物学中的一个基本问题是，生境碎片化如何影响种群间遗传多样性的分布以及种群适应当地条件的能力。在我的研究中，我使用有效种群大小(Ne)作为衡量种群遗传多样性的指标，并检查了在复杂地形中发现的鱼类种群Ne的决定机制。有效的种群规模通过与种群持久性和进化潜力的联系，对物种保护具有重要意义。大多数物种以不同程度的基因流(元种群)相互连接的种群网络的形式自然出现。因此，遗传多样性的模式是影响本地种群ne‘s(随机损失、局部适应性选择、基因流)和元种群的有效规模(meta-ne)的机制的产物。基因流倾向于通过抵消遗传多样性的随机损失来增加当地种群的Ne，而定向选择可能会减少多样性。对于元种群，理论预测，如果当地人口对下一代的贡献不均衡，那么分散系统的元种群将比类似规模的泛灵系统的元种群小。然而，在复杂的、层级排列的树枝状环境中，预测的Meta-Ne可能大于局部Ne的总和。例如，树状分水岭具有本地种群的层级排列，这通常会导致不对称的基因流动。景观中的环境变化也会影响Meta-ne，使种群面临不同的选择压力。 我的长期目标是阐明鱼类在空间复杂的集合种群系统中局部适应的基因组基础，并确定基因流动及其不对称性如何影响中性和适应性遗传多样性的模式。我将研究几个温带后冰期景观(新斯科舍省、纽芬兰、拉布拉多和巴塔哥尼亚)的系统，它们在碎片化和连通性方面存在差异。这些树突引流在大小和复杂性上不同，因此可能在不对称基因流和适应过程的相对重要性上有所不同。我还将在包含不同选择压力(水的pH值、透明度、生产力)的湖泊的景观中，比较生活史特征非常不同的共地物种的遗传多样性模式。其目标将是理清基因流动、适应过程和物种生活史对局部NE和Meta-NE的影响。其中一些工作将在新斯科舍省的West River Sheet港排水系统中进行，这是一个高度复杂的树枝状系统，由近20个相互关联的湖泊组成，环境变量不同，包含三个丰富的共生物种，它们在一些关键的生活史特征上存在差异：带状剑鱼、黄鲈和白色吸盘鱼。我正在进行的关于鲑鱼物种的类似和相关问题的研究将继续集中在纽芬兰的亨伯河上游水系，而在巴塔哥尼亚，我将研究广泛分布的斑点银河的殖民模式和对盐度的适应。在连接光谱的另一端，我也研究海洋物种，包括大西洋鲱鱼，一种高度丰富和分布广泛的中上层鱼类。这项研究将构成对关于连通性对本地人口Ne和元Ne之间关系的影响的理论预测的一些首批经验检验，并将使我们对该理论对于理解真实系统的有用性有一些了解，并有助于为进一步的理论发展指明方向。