Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara, Italy.
Department of Biology, University of Padova, Padova, Italy.
Conserv Biol. 2023 Dec;37(6):e14133. doi: 10.1111/cobi.14133. Epub 2023 Sep 28.
Reduction in population size, with its predicted effects on population fitness, is the most alarming anthropogenic impact on endangered species. By introducing compatible individuals, genetic rescue (GR) is a promising but debated approach for reducing the genetic load unmasked by inbreeding and for restoring the fitness of declining populations. Although GR can improve genetic diversity and fitness, it can also produce loss of ancestry, hampering local adaptation, or replace with introduced variants the unique genetic pools evolved in endemic groups. We used forward genetic simulations based on empirical genomic data to assess fitness benefits and loss of ancestry risks of GR in the Apennine brown bear (Ursus arctos marsicanus). There are approximately 50 individuals of this isolated subspecies, and they have lower genetic diversity and higher inbreeding than other European brown bears, and GR has been suggested to reduce extinction risks. We compared 10 GR scenarios in which the number and genetic characteristics of migrants varied with a non-GR scenario of simple demographic increase due to nongenetic factors. The introduction of 5 individuals of higher fitness or lower levels of deleterious mutations than the target Apennine brown bear from a larger European brown bear population produced a rapid 10-20% increase in fitness in the subspecies and up to 22.4% loss of ancestry over 30 generations. Without a contemporary demographic increase, fitness started to decline again after a few generations. Doubling the population size without GR gradually increased fitness to a comparable level, but without losing ancestry, thus resulting in the best strategy for the Apennine brown bear conservation. Our results highlight the importance for management of endangered species of realistic forward simulations grounded in empirical whole-genome data.
种群规模的减少及其对种群适应性的预测影响，是对濒危物种最具威胁的人为影响。通过引入相容个体，遗传拯救（GR）是一种有前途但备受争议的方法，可减少因近交而暴露的遗传负荷，并恢复衰退种群的适应性。尽管 GR 可以提高遗传多样性和适应性，但它也可能导致遗传血统的丧失，阻碍局部适应，或者用引入的变体取代在地方性群体中进化的独特遗传库。我们使用基于经验基因组数据的正向遗传模拟来评估遗传拯救在亚平宁棕熊（Ursus arctos marsicanus）中的适应性收益和遗传血统丧失风险。这个孤立亚种大约有 50 只个体，它们的遗传多样性较低，近交程度较高，与其他欧洲棕熊相比，遗传拯救被认为可以降低灭绝风险。我们比较了 10 种 GR 情景，其中移民的数量和遗传特征因非遗传因素而变化，与非 GR 情景的简单人口增长相比。从更大的欧洲棕熊种群中引入 5 只适应性更高或有害突变水平较低的个体，可使亚种的适应性迅速提高 10-20%，在 30 代内遗传血统丧失高达 22.4%。如果没有当代人口增长，适应性在几代后又开始下降。不进行 GR 而使种群规模翻倍，适应性逐渐提高到可比水平，但不会失去遗传血统，因此是亚平宁棕熊保护的最佳策略。我们的研究结果强调了基于经验全基因组数据的现实正向模拟对于濒危物种管理的重要性。
