Data from: The genetic legacy of 50 years of desert bighorn sheep translocations

Conservation biologists have increasingly used translocations to mitigate population declines and restore locally extirpated populations. Genetic data can guide the selection of source populations for translocations and help evaluate restoration success. Bighorn sheep (Ovis canadensis) are a managed big game species that suffered widespread population extirpations across western North America throughout the early 1900’s. Subsequent translocation programs have successfully re-established many formally extirpated bighorn herds, but most of these programs pre-date genetically-informed management practices. The state of Nevada presents a particularly well-documented case of decline followed by restoration of extirpated herds. Desert bighorn sheep (O. c. nelsoni) populations declined to less than 3,000 individuals restricted to remnant herds in the Mojave Desert and a few locations in the Great Basin Desert. Beginning in 1968, the Nevada Department of Wildlife translocated ~2,000 individuals from remnant populations to restore previously extirpated areas, possibly establishing herds with mixed ancestries. Here we examined genetic diversity and structure among remnant herds and the genetic consequences of translocation from these herds using a genotyping-by-sequencing approach to genotype 17,095 loci in 303 desert bighorn sheep. We found a signal of population genetic structure among remnant Mojave Desert populations, even across geographically proximate mountain ranges. Further, we found evidence of a genetically distinct, potential relict herd from a previously hypothesized Great Basin lineage of desert bighorn sheep. The genetic structure of source herds was clearly reflected in translocated populations. In most cases, herds retained genetic evidence of multiple translocation events and subsequent admixture when founded from multiple remnant source herds. Our results add to a growing literature on how population genomic data can be used to guide and monitor restoration programs.保护生物学家愈发频繁地采用种群易地移植（translocation）手段，以缓解种群衰退进程并恢复局域灭绝的本土种群。遗传数据能够为易地移植的源种群遴选提供科学指导，并助力评估修复项目的实施成效。大角羊（Ovis canadensis）是一类受管护的大型猎用物种，在20世纪早期，其种群在北美西部大范围发生局域灭绝。后续开展的易地移植项目已成功重建了诸多此前局域灭绝的大角羊种群，但绝大多数这类项目均早于基于遗传信息的管护实践出现的时间。内华达州的相关案例记录尤为详尽：该州大角羊种群先经历了显著衰退，随后完成了局域灭绝种群的恢复工作。沙漠大角羊（O. c. nelsoni）的种群数量锐减至不足3000只，仅残存于莫哈韦沙漠的零散种群以及大盆地沙漠的少数区域。自1968年起，内华达州野生动物部门从残存种群中迁移约2000只个体，以恢复此前局域灭绝的栖息区域，此举或建立了具有混合血统的种群。本研究采用测序分型（genotyping-by-sequencing）技术，对303只沙漠大角羊的17095个基因位点进行基因分型，以此分析残存种群的遗传多样性与遗传结构，以及源自这些残存种群的易地移植所产生的遗传效应。研究发现，即便在地理上邻近的山脉之间，莫哈韦沙漠的残存种群也存在显著的种群遗传结构信号。此外，本研究发现了一个遗传分化显著的潜在孑遗种群的证据，该种群隶属于此前假说中的大盆地沙漠大角羊血统支系。易地移植种群的遗传结构清晰地反映了其源种群的遗传结构。在多数情况下，当种群由多个残存源种群建立时，其仍保留了多次易地移植事件以及后续遗传混合的遗传证据。本研究结果为日益增长的相关研究文献增添了新的实证支持，即种群基因组数据可用于指导并监测野生动物修复项目的开展。