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.

保护生物学家日益采用种群易地转移（translocation）手段以缓解种群衰退，并恢复局域灭绝的本土种群。遗传数据可为易地转移的源种群选择提供指导，并助力评估恢复成效。大角羊（Ovis canadensis）是一种受管理的大型猎用物种，在20世纪早期，其在北美西部的种群曾遭遇大范围局域灭绝。后续的易地转移项目已成功重建了诸多此前正式局域灭绝的大角羊种群，但此类项目大多早于基于遗传信息的管理实践出现。内华达州便是一个记录尤为详实的种群衰退与灭绝种群恢复案例。沙漠大角羊（O. c. nelsoni）的种群数量一度缩减至不足3000只，仅残存于莫哈韦沙漠的残余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余种群中转移约2000只个体，以恢复此前已局域灭绝的栖息区域，此举或构建出具有混合血统的种群。本研究借助测序分型（genotyping-by-sequencing, GBS）技术，对303只沙漠大角羊的17095个基因位点进行分型，以此分析残余种群的遗传多样性与群体结构，以及从这些残余种群开展易地转移所带来的遗传效应。研究发现，莫哈韦沙漠的残余种群之间存在群体遗传结构信号，即便在地理上邻近的山脉间亦是如此。此外，本研究发现了一支遗传上独特的潜在残余种群的证据，该种群隶属于此前假说中的大盆地沙漠大角羊支系。源种群的遗传结构在易地转移的种群中得到了清晰体现。在多数情况下，由多个残余源种群建立的种群仍保留着多次易地转移事件以及后续遗传混合的遗传信号。本研究结果进一步丰富了相关研究文献，这些研究旨在探讨如何利用群体基因组数据指导并监测恢复项目。