Gene flow is an enigmatic evolutionary force because it can limit adaptation but may also rescue small populations from inbreeding depression [1-3]. Several iconic examples of genetic rescue-increased population growth caused by gene flow [4, 5]-have reversed population declines [6, 7]. However, concerns about outbreeding depression and maladaptive gene flow limit the use of human-mediated gene flow in conservation [8, 9]. Rescue effects of immigration through demographic and/or genetic mechanisms have received theoretical and empirical support, but studies that monitor initial and long-term effects of gene flow on individuals and populations in the wild are lacking. Here, we used individual-based mark-recapture, multigenerational pedigrees, and genomics to test the demographic and evolutionary consequences of manipulating gene flow in two isolated, wild Trinidadian guppy populations. Recipient and source populations originated from environments with different predation, flow, and resource regimes [10]. We documented 10-fold increases in population size following gene flow and found that, on average, hybrids lived longer and reproduced more than residents and immigrants. Despite overall genomic homogenization, alleles potentially associated with local adaptation were not entirely swamped by gene flow. Our results suggest that genetic rescue was caused not just by increasing individual genetic diversity, rather new genomic variation from immigrants combined with alleles from the recipient population resulted in highly fit hybrids and subsequent increases in population size. Contrary to the classic view of maladaptive gene flow, our study reveals conditions under which immigration can produce long-term fitness benefits in small populations without entirely swamping adaptive variation.

中文翻译：

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野生种群遗传救援的基因组和适应性后果。

基因流是一种神秘的进化力，因为它可以限制适应性，但也可以使小种群从近亲衰退中解救出来[1-3]。由基因流[4，5]引起的基因拯救增加人口增长的几个标志性例子逆转了人口下降的趋势[6，7]。然而，对近亲抑郁和适应不良基因流的关注限制了人类介导的基因流在保护中的应用[8，9]。通过人口和/或遗传机制对移民的营救效应得到了理论和经验的支持，但是缺乏监测基因流对野生个体和种群的初始和长期影响的研究。在这里，我们使用了基于个人的标记夺回，多代谱系，基因组学和基因组学，以测试在两个孤立的野生特立尼达孔雀鱼种群中操纵基因流的人口统计学和进化结果。接收者和来源人口起源于具有不同掠食，流量和资源制度的环境[10]。我们记录了基因流动后种群数量增加了10倍的情况，发现平均而言，杂种比居民和移民的寿命更长，繁殖能力更高。尽管整体基因组均质化，潜在与局部适应性相关的等位基因并未完全被基因流淹没。我们的结果表明，基因拯救不仅是由于个体遗传多样性的增加，而是来自移民的新基因组变异与受者群体的等位基因相结合，导致了高度适合的杂种和随后种群数量的增加。