Department of Biology and Genomics and Bioinformatics Cluster, University of Central Florida, Orlando, FL 32816, USA.
Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, Naples, FL 34114, USA.
J Hered. 2022 Oct 21;113(5):491-499. doi: 10.1093/jhered/esac037.
Genetic admixture is a biological event inherent to genetic rescue programs aimed at the long-term conservation of endangered wildlife. Although the success of such programs can be measured by the increase in genetic diversity and fitness of subsequent admixed individuals, predictions supporting admixture costs to fitness due to the introduction of novel deleterious alleles are necessary. Here, we analyzed nonsynonymous variation from conserved genes to quantify and compare levels of mutation load (i.e. proportion of deleterious alleles and genotypes carrying these alleles) among endangered Florida panthers and non-endangered Texas pumas. Specifically, we used canonical (i.e. non-admixed) Florida panthers, Texas pumas, and F1 (canonical Florida × Texas) panthers dating from a genetic rescue program and Everglades National Park panthers with Central American ancestry resulting from an earlier admixture event. We found neither genetic drift nor selection significantly reduced overall proportions of deleterious alleles in the severely bottlenecked canonical Florida panthers. Nevertheless, the deleterious alleles identified were distributed into a disproportionately high number of homozygous genotypes due to close inbreeding in this group. Conversely, admixed Florida panthers (either with Texas or Central American ancestry) presented reduced levels of homozygous genotypes carrying deleterious alleles but increased levels of heterozygous genotypes carrying these variants relative to canonical Florida panthers. Although admixture is likely to alleviate the load of standing deleterious variation present in homozygous genotypes, our results suggest that introduced novel deleterious alleles (temporarily present in heterozygous state) in genetically rescued populations could potentially be expressed in subsequent generations if their effective sizes remain small.
遗传混合是遗传拯救计划中固有的生物学事件，旨在长期保护濒危野生动物。尽管这些计划的成功可以通过增加遗传多样性和随后混合个体的适应度来衡量，但需要预测由于引入新的有害等位基因而导致适应度的混合成本。在这里，我们分析了保守基因中的非同义变异，以量化和比较濒危佛罗里达黑豹和非濒危德克萨斯美洲狮之间的突变负荷水平（即有害等位基因的比例和携带这些等位基因的基因型）。具体来说，我们使用了来自遗传拯救计划的典型（即未混合）佛罗里达黑豹、德克萨斯美洲狮和 F1（典型佛罗里达×德克萨斯）黑豹，以及来自早期混合事件的大沼泽地国家公园具有中美洲血统的黑豹。我们发现，无论是遗传漂变还是选择，都没有显著降低严重瓶颈状态下典型佛罗里达黑豹中有害等位基因的总体比例。尽管如此，由于该群体的近亲繁殖，确定的有害等位基因分布在不成比例的高数量的纯合基因型中。相反，混合的佛罗里达黑豹（无论是与德克萨斯州还是中美洲有血统关系）表现出携带有害等位基因的纯合基因型水平降低，但携带这些变体的杂合基因型水平增加，与典型的佛罗里达黑豹相比。尽管混合可能减轻纯合基因型中存在的有害等位基因的负担，但我们的结果表明，在遗传上获救的种群中引入的新的有害等位基因（暂时处于杂合状态）如果其有效大小仍然较小，则可能在下一世代表达。
