Wilder Aryn P, Steiner Cynthia C, Hendricks Sarah, Haller Benjamin C, Kim Chang, Korody Marisa L, Ryder Oliver A
Conservation Genetics San Diego Zoo Wildlife Alliance Escondido California USA.
Institute for Interdisciplinary Data Sciences University of Idaho Moscow Idaho USA.
Evol Appl. 2024 Apr 11;17(4):e13683. doi: 10.1111/eva.13683. eCollection 2024 Apr.
As biodiversity loss outpaces recovery, conservationists are increasingly turning to novel tools for preventing extinction, including cloning and in vitro gametogenesis of biobanked cells. However, restoration of populations can be hindered by low genetic diversity and deleterious genetic load. The persistence of the northern white rhino () now depends on the cryopreserved cells of 12 individuals. These banked genomes have higher genetic diversity than southern white rhinos (), a sister subspecies that successfully recovered from a severe bottleneck, but the potential impact of genetic load is unknown. We estimated how demographic history has shaped genome-wide genetic load in nine northern and 13 southern white rhinos. The bottleneck left southern white rhinos with more fixed and homozygous deleterious alleles and longer runs of homozygosity, whereas northern white rhinos retained more deleterious alleles masked in heterozygosity. To gauge the impact of genetic load on the fitness of a northern white rhino population restored from biobanked cells, we simulated recovery using fitness of southern white rhinos as a benchmark for a viable population. Unlike traditional restoration, cell-derived founders can be reintroduced in subsequent generations to boost lost genetic diversity and relieve inbreeding. In simulations with repeated reintroduction of founders into a restored population, the fitness cost of genetic load remained lower than that borne by southern white rhinos. Without reintroductions, rapid growth of the restored population (>20-30% per generation) would be needed to maintain comparable fitness. Our results suggest that inbreeding depression from genetic load is not necessarily a barrier to recovery of the northern white rhino and demonstrate how restoration from biobanked cells relieves some constraints of conventional restoration from a limited founder pool. Established conservation methods that protect healthy populations will remain paramount, but emerging technologies hold promise to bolster these tools to combat the extinction crisis.
随着生物多样性丧失速度超过恢复速度，保护主义者越来越多地转向使用新工具来防止物种灭绝，包括克隆和对生物样本库中的细胞进行体外配子发生。然而，种群恢复可能会受到低遗传多样性和有害遗传负荷的阻碍。北方白犀牛（）的存续现在依赖于12个个体的冷冻保存细胞。这些保存的基因组比南方白犀牛（）具有更高的遗传多样性，南方白犀牛是一个姐妹亚种，曾成功从严重瓶颈中恢复过来，但遗传负荷的潜在影响尚不清楚。我们估计了种群历史如何塑造了9头北方白犀牛和13头南方白犀牛全基因组的遗传负荷。瓶颈使南方白犀牛留下了更多固定和纯合的有害等位基因以及更长的纯合片段，而北方白犀牛保留了更多杂合状态下被掩盖的有害等位基因。为了评估遗传负荷对从生物样本库细胞恢复的北方白犀牛种群适应性的影响，我们以南方白犀牛的适应性为可行种群的基准，模拟了恢复过程。与传统恢复不同，细胞来源的奠基者可以在后代中重新引入，以增加丧失的遗传多样性并缓解近亲繁殖。在将奠基者反复重新引入恢复种群的模拟中，遗传负荷的适应性成本仍低于南方白犀牛所承受的成本。如果不进行重新引入，则需要恢复种群快速增长（每代>20 - 30%）以维持相当的适应性。我们的结果表明，遗传负荷导致的近亲繁殖衰退不一定是北方白犀牛恢复的障碍，并证明了从生物样本库细胞进行恢复如何缓解了有限奠基者群体传统恢复的一些限制。既定的保护健康种群的方法仍将至关重要，但新兴技术有望加强这些工具，以应对灭绝危机。
