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生境景观，并应对人为构建的阻隔屏障，是保护生物学领域的核心研究方向之一。现有基于移动、扩散或基因流评估功能连通性的研究，通常仅依托单一观测时段，极少考虑随时间推移产生的动态变化。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，对比了其在阻隔屏障两侧的遗传结构与基因流模式。鉴于近期观测到一种呼吸道病原体意外跨越了此前被认定为基因流阻隔的州际公路，我们提出假说：大角羊对该屏障的交互模式已发生改变，且集合种群结构的变化会影响基因流、遗传多样性与连通性水平。种群归属检验、遗传结构分析与基因重捕获结果显示：2013–2015年间，大角羊至少在一处点位跨越了该州际公路，显著降低了两个种群间的遗传分化水平；但这一结果也佐证了早期研究的结论——2000–2003年间此类跨屏障移动极为罕见，甚至未曾被观测到。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结构分化程度下降。通过新通路产生基因交流的种群，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移动模式与分布范围变化，但多数种群的遗传特征仍保持稳定。综上，仅在两代种群的时间尺度内，我们便观测到结构连通性与功能连通性均发生了变化，但这种变化仅局限于特定区域。针对物种的移动模式应开展周期性重访研究，以支撑科学的保护管理决策——在动态且生境破碎化的生态系统中，这一点尤为重要。