Effective population size and connectivity in fish

进化生物学中的一个基本概念是有效种群规模（Ne）。Ne反映了“理想”种群的规模，其每一代的随机遗传变化率与所研究的实际种群（人口普查规模N）相同。这个概念是保护遗传学的核心，因为它与近亲繁殖减少、种群持久性和进化潜力有关。有效规模通常比普查规模小得多。随着时间的推移，种群规模的波动，性别比例的不平等以及一生中繁殖成功率的差异导致了自然界中普遍观察到的低Ne/N比率。如此低的比率表明，即使在人口普查规模仍然相对较大的情况下，人口也可能遭受遗传多样性的丧失。因此，了解影响Ne的机制、其与N和基因流(m)的关系以及它们之间的相互作用对于理解影响生物多样性的机制至关重要。我的长期研究目标是了解影响Ne和m的过程，以及它们与N的关系，并确定Ne可用于预测种群持久性的条件。我打算比较同域鱼类种群中Ne和m的模式，以解开生活史和环境的影响。我还计划重建祖先的种群动态；我将比较Ne的历史变化和跨物种祖先种群瓶颈的时间，并将这些信息与地质形态过程和过去的气候变化（第四纪）联系起来。目标是确定共存物种种群中当前和历史上的Ne和m的模式有多相似，并检查生活史、生态学、地貌和气候在产生这些模式中所起的作用。实地考察在两个截然不同的温带系统中进行：北部的“鲑鱼”系统和巴塔哥尼亚系统。两者都存在于冰川后的景观中。北部鲑鱼系统包括大西洋鲑鱼、溪鳟鱼和纽芬兰和拉布拉多的北极鲑鱼。巴塔哥尼亚系统包括两种广泛分布的本地巴塔哥尼亚鱼类。在这两种情况下，物种都存在于各种生态环境中。

A fundamental concept in evolutionary biology is that of effective population size (Ne). Ne reflects the size of an "ideal" population experiencing the same rate of random genetic change per generation as the actual population under study (census size N). The concept is central to conservation genetics because of its links to inbreeding depression, population persistence and evolutionary potential. Effective sizes are typically much smaller than census sizes. Fluctuating population size over time, unequal sex ratio and variance in life time reproductive success contribute to the low Ne/N ratios commonly observed in nature. Such low ratios suggest that populations may be subject to the loss of genetic diversity even when census sizes are still relatively large. Knowledge of the mechanisms that affect Ne, its relationship with N and with gene flow (m) and their interaction is thus critical for understanding the mechanisms that affect biodiversity. My long term research goals are to understand the processes that affect Ne and m, and their relationship with N, and to identify the conditions under which Ne can be used to predict population persistence. I intend to compare patterns of Ne and m across sympatric populations of fish species to disentangle the influences of life history and environment. I also plan to reconstruct ancestral population dynamics; I will compare historical changes in Ne and timing of ancestral population bottlenecks across species and will relate this information to geo-morphological processes and past climatic changes (Quaternary). The goal is to determine how similar current and historic patterns of Ne and m are for populations of coexisting species and to examine the roles played by life histories and ecologies vs. geomorphology and climate in producing these patterns. Fieldwork takes place in two contrasting temperate systems: A northern "Salmonid" system, and a Patagonian system. Both are found in post-glacial landscapes. The northern salmonid system includes Atlantic salmon, brook trout, and Arctic char in Newfoundland and Labrador. The Patagonian system comprises two widely distributed native Patagonian fishes. In both cases, species are found in a variety of ecological settings.