Clark Meaghan I, Hileman Eric T, Moore Jennifer A, Faust Lisa J, Junge Randall E, Reid Brendan N, Bradke Danielle R, Bradburd Gideon S, Fitzpatrick Sarah W
Department of Integrative Biology, Michigan State University, East Lansing, MI 48824.
Ecology, Evolution, and Behavior Program, Michigan State University, East Lansing, MI 48824.
Proc Natl Acad Sci U S A. 2025 Aug 26;122(34):e2501745122. doi: 10.1073/pnas.2501745122. Epub 2025 Aug 18.
Small and fragmented populations are at high risk of local extinction, in part because of elevated inbreeding and subsequent inbreeding depression. A major conservation priority is to identify the mechanisms and extent of inbreeding depression in small populations. The eastern massasauga () rattlesnake is listed as Federally Threatened in the United States, having experienced significant habitat fragmentation and concomitant population declines over the past 200 years. Here, we use long-term monitoring of two wild populations of eastern massasaugas in Michigan to estimate the extent of inbreeding in each population, identify mechanisms that generate inbreeding, and test for the impact of inbreeding on fitness. Using targeted genomic data and spatial coordinates of capture locations from over 1000 individuals, we find evidence of inbreeding and link inbreeding to spatial kinship structure within populations, possibly driven by limited dispersal. We reconstruct multigenerational pedigrees for each population to measure reproductive output and use long-term capture-recapture data to estimate individual survival (i.e., the two major components of fitness). We find evidence of inbreeding depression in both fitness metrics. The 5% most inbred individuals are 13.5% less likely to have any surviving offspring and have 11.6% lower annual survival compared to all less inbred individuals. By combining genomics and long-term monitoring data, we are able to link the life history of eastern massasaugas to inbreeding and detect relationships between fitness and inbreeding. These insights provide important conservation context for future management and for understanding how spatial structure can generate inbreeding depression even at fine spatial scales.
小型且分散的种群面临着很高的局部灭绝风险，部分原因是近亲繁殖增加以及随之而来的近亲繁殖衰退。一个主要的保护重点是确定小种群中近亲繁殖衰退的机制和程度。东部马萨索加响尾蛇在美国被列为联邦濒危物种，在过去200年里经历了显著的栖息地破碎化以及随之而来的种群数量下降。在这里，我们通过对密歇根州两个东部马萨索加野生种群的长期监测，来估计每个种群的近亲繁殖程度，确定产生近亲繁殖的机制，并测试近亲繁殖对适合度的影响。利用来自1000多个个体的靶向基因组数据和捕获地点的空间坐标，我们发现了近亲繁殖的证据，并将近亲繁殖与种群内的空间亲属结构联系起来，这可能是由有限的扩散驱动的。我们为每个种群重建多代谱系以衡量繁殖输出，并使用长期的捕获 - 再捕获数据来估计个体存活率（即适合度的两个主要组成部分）。我们在这两个适合度指标中都发现了近亲繁殖衰退的证据。与所有近亲繁殖程度较低的个体相比，近亲繁殖程度最高的5%个体产生任何存活后代的可能性低13.5%，年存活率低11.6%。通过结合基因组学和长期监测数据，我们能够将东部马萨索加的生活史与近亲繁殖联系起来，并检测适合度与近亲繁殖之间的关系。这些见解为未来的管理以及理解空间结构如何即使在精细的空间尺度上也能产生近亲繁殖衰退提供了重要的保护背景。
