Due to increasing anthropogenic impacts, many species survive only in small and isolated populations. Active conservation management to reduce extinction risk includes increasing habitat connectivity, translocations from captive populations, or intensive surveillance of highly protected closed populations. Advances in sequencing technology mean that it is now possible to consider the genomic impacts of such strategies, as a proxy for variation in individual fitness. Using whole genome sequences from critically endangered eastern black rhinoceros ( Diceros bicornis michaeli ), we compare the consequences of different types of conservation efforts, based on cohorts of offspring resulting from parents from different sources. Based on the fraction of the genome in runs of homozygosity (ROH) of different lengths, we found lower inbreeding in offspring of individuals that had either been translocated from ex-situ populations (F ROH>1Mb = 0.047) or dispersed between proximate native populations (F ROH>1Mb = 0.065) compared to the intensively managed closed population from which the migrant moved (F ROH>1Mb = 0.112). However, the benefit of such movement was removed after only a few generations of closed breeding (F ROH>1Mb = 0.149). Although sample size restricted power to detect significance of differences, the relative abundance of highly deleterious mutations was higher for offspring resulting from translocation compared to the other cohorts and this load was sheltered by higher heterozygosity, which could increase risks of inbreeding depression if inbreeding subsequently occurs. In contrast, native dispersers reduced the negative effects of inbreeding without compromising the benefits of past purging of deleterious mutations. Our study highlights the importance of natural dispersal and reiterates the importance of maintaining habitat corridors between populations.

中文翻译：

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自然扩散比易位更能降低东部黑犀牛近亲繁殖抑制的风险 （ Diceros bicornis michaeli ）

由于人为影响的增加，许多物种只能在小而孤立的种群中生存。为降低灭绝风险而采取的积极保护管理包括增加栖息地的连通性、圈养种群的易位或对高度保护的封闭种群进行密集监测。测序技术的进步意味着现在可以考虑此类策略的基因组影响，作为个体适应性变化的代表。使用极度濒危的东部黑犀牛 （ Diceros bicornis michaeli ） 的全基因组序列，我们根据来自不同来源的父母产生的后代队列，比较了不同类型保护工作的后果。基于不同长度的纯合性 （ROH） 运行中的基因组分数，我们发现从异位种群转移的个体 （F ROH>1Mb = 0.047） 或分散在邻近本地种群之间的个体的后代 （F ROH>1Mb = 0.065） 与移民迁出的密集管理的封闭种群 （F ROH>1Mb = 0.112） 相比。然而，这种运动的好处在仅仅几代封闭育种后就被消除了 （F ROH>1Mb = 0.149）。尽管样本量限制了检测差异显着性的能力，但与其他队列相比，易位导致的后代高度有害突变的相对丰度更高，并且这种负荷被更高的杂合性所掩盖，如果近亲繁殖随后发生，这可能会增加近亲繁殖抑制的风险。相比之下，天然分散剂减少了近亲繁殖的负面影响，而不会影响过去清除有害突变的好处。 我们的研究强调了自然扩散的重要性，并重申了维持种群之间栖息地走廊的重要性。