Data from: Multiple estimates of effective population size for monitoring a long-lived vertebrate: application to Yellowstone grizzly bears

Effective population size (Ne) is a key parameter for monitoring the genetic health of threatened populations because it reflects a population’s evolutionary potential and risk of extinction due to genetic stochasticity. However, its application to wildlife monitoring has been limited because it is difficult to measure in natural populations. The isolated and well-studied population of grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem provides a rare opportunity to examine the usefulness of different Ne estimators for monitoring. We genotyped 729 Yellowstone grizzly bears using 20 microsatellites and applied three single-sample estimators to examine contemporary trends in generation interval (GI), effective number of breeders (Nb), and Ne during 1982–2007. We also used multi-sample methods to estimate variance (NeV) and inbreeding Ne (NeI). Single-sample estimates revealed positive trajectories, with over a 4-fold increase in Ne (≈100 to 450) and near doubling of the GI (≈8 to 14) from the 1980s to 2000s. NeV (240–319) and NeI (256) were comparable with the harmonic mean single-sample Ne (213) over the time period. Reanalyzing historical data, we found NeV increased from ≈80 in the 1910s–1960s to ≈280 in the contemporary population. The ratio of effective to total census size (Ne/Nc) was stable and high (0.42–0.66) compared to previous brown bear studies. These results support independent demographic evidence for Yellowstone grizzly bear population growth since the 1980s. They further demonstrate how genetic monitoring of Ne can complement demographic-based monitoring of Nc and vital rates, providing a valuable tool for wildlife managers.

有效种群数量（Effective population size, Ne）是监测受威胁种群遗传健康状况的关键参数，因其可反映种群的进化潜力以及由遗传随机性引发的灭绝风险。然而，由于难以在自然种群中直接测定，该指标在野生动物监测中的应用一直受到限制。大黄石生态系统（Greater Yellowstone Ecosystem）中孤立且被深入研究的灰熊（Ursus arctos）种群，为探究不同Ne估计器在监测中的实用性提供了难得的契机。我们利用20个微卫星标记对729只黄石灰熊进行了基因分型，并采用3种单样本估计器，分析了1982年至2007年间世代间隔（generation interval, GI）、有效繁殖个体数（effective number of breeders, Nb）以及Ne的当代变化趋势。同时，我们还使用多样本方法分别估计了方差有效种群数量（variance Ne, NeV）与近交有效种群数量（inbreeding Ne, NeI）。单样本估计结果显示出正向变化轨迹：从1980年代至2000年代，Ne增长超过4倍（约从100增至450），世代间隔则几乎翻倍（约从8增至14）。研究期间，NeV（240~319）与NeI（256）与单样本Ne的调和均值（213）处于相近水平。通过重新分析历史数据，我们发现NeV从1910年代至1960年代的约80增长至当代种群的约280。与此前针对棕熊的相关研究相比，有效种群数量与总普查种群数量的比值（Ne/Nc）稳定且处于较高水平（0.42~0.66）。这些结果为1980年代以来黄石灰熊种群增长提供了独立的遗传学证据。本研究进一步证明，对Ne的遗传监测可辅助基于普查种群数量与生命率的人口统计学监测，为野生动物管理者提供了一项极具价值的工具。