Data from: Assessing changes in functional connectivity in a desert bighorn sheep metapopulation after two generations

Determining how species move across complex and fragmented landscapes and interact with human-made barriers is a major research focus in conservation. Studies estimating functional connectivity from movement, dispersal, or gene flow usually rely on a single study period, and rarely consider variation over time. We contrasted genetic structure and gene flow across barriers for a metapopulation of desert bighorn sheep (Ovis canadensis nelsoni) using genotypes collected 2000–2003 and 2013–2015. Based on the recently observed but unexpected spread of a respiratory pathogen across an interstate highway previously identified as a barrier to gene flow, we hypothesized that bighorn sheep changed how they interacted with that barrier, and that shifts in metapopulation structure influenced gene flow, genetic diversity, and connectivity. Population assignment tests, genetic structure, and genetic recapture demonstrated that bighorn sheep crossed the interstate highway in at least one location in 2013-2015, sharply reducing genetic structure between two populations, but supported conclusions of an earlier study that such crossings were very infrequent or unknown in 2000-2003. A recently expanded population established new links and caused decreases in genetic structure among multiple populations. Genetic diversity showed only slight increases in populations linked by new connections. Genetic structure and assignments revealed other previously undetected changes in movements and distribution, but much was consistent. Thus, we observed changes in both structural and functional connectivity over just two generations, but only in specific locations. Movement patterns of species should be revisited periodically to enable informed management, particularly in dynamic and fragmented systems.探明物种如何穿越复杂破碎化的景观，并与人工屏障产生交互作用，是保护生物学领域的核心研究议题之一。基于运动、扩散或基因流（gene flow）估算功能连通性（functional connectivity）的研究，通常仅依托单个研究周期开展，极少考虑随时间产生的变化。本研究针对沙漠大角羊（Ovis canadensis nelsoni）的集合种群（metapopulation），利用2000–2003年与2013–2015年采集的基因型数据，对比分析了其跨越屏障的遗传结构（genetic structure）与基因流模式。基于近期观测到的、意外的呼吸道病原体跨州际高速公路传播现象——该公路此前被认定为基因流的屏障——我们提出假说：大角羊与该屏障的交互方式已发生改变，且集合种群结构的变化会影响基因流、遗传多样性与种群连通性。种群归属检验、遗传结构分析与遗传重捕获（genetic recapture）结果表明：2013–2015年间，大角羊至少在一处点位跨越了该州际公路，大幅降低了两个种群间的遗传分化；但这一结果也佐证了早期研究的结论——2000–2003年间此类跨径极为罕见，甚至未被观测到。一个近期发生扩张的种群建立了新的扩散通路，导致多个种群间的遗传分化水平下降。通过新通路实现基因交流的种群，其遗传多样性仅出现小幅提升。遗传结构分析与种群归属检验还揭示了此前未被发现的运动与分布模式变化，但多数种群特征仍保持稳定。综上，本研究仅在两代种群周期内，便观测到结构连通性与功能连通性的变化，但该变化仅局限于特定区域。对于物种的运动模式，应定期开展重新评估，以制定科学合理的管理策略，在动态且破碎化的生态系统中尤为如此。