Abstract Reliability of population size and density estimates is one of the most contentious issues when evaluating the conservation status of species. Non-invasive DNA monitoring, combined with spatially explicit capture-recapture approaches (SCR), is recurrently presented as a reliable procedure to achieve accurate, precise and feasible estimates. However, conservation practitioners frequently face the dilemma of which molecular marker type would perform better for their objectives. Here, using as case study the eastern subpopulation of the endangered Cantabrian brown bear, and the same dataset of non-invasive samples, we evaluated which molecular marker perform better (microsatellites vs. SNPs), and whether the selection of the marker could impact on estimates. Our results show similar posterior estimates for bear density and for the scale parameter, resulting in consistent population estimates, around 50 bears, regardless the molecular marker type selected, microsatellites: 48.4 (95%BCI = 33.8–67.3) or SNPs: 52.7 (95%BCI = 36.0–74.8). Using our dataset, we provide evidence for the importance of running several replicates for both microsatellites and SNPs when genotyping non-invasive samples, and how for the same number of molecular markers, microsatellites were statistically more powerful. The positive trend observed in small large carnivore populations requires the adaptation of monitoring approaches. The quality of indexes commonly used, such as the minimum annual counts of females with cubs of the year in our study case, may be more difficult to maintain over time as populations increase in size and range. We therefore recommend the implementation of a regular monitoring based on non-invasive DNA monitoring and SCR approaches.

中文翻译：

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无论分子标记类型如何，基于 DNA 的一致的熊种群估计

摘要 种群规模和密度估计的可靠性是评估物种保护状况时最有争议的问题之一。无创 DNA 监测与空间明确的捕获-再捕获方法 (SCR) 相结合，被反复提出作为实现准确、精确和可行估计的可靠程序。然而，保护从业者经常面临哪种分子标记类型会更好地实现其目标的困境。在这里，以濒临灭绝的坎塔布连棕熊的东部亚群和相同的非侵入性样本数据集作为案例研究，我们评估了哪个分子标记表现更好（微卫星与 SNP），以及标记的选择是否会影响估计。我们的结果显示了熊密度和尺度参数的类似后验估计，导致一致的种群估计，大约 50 只熊，无论选择的分子标记类型，微卫星：48.4 (95%BCI = 33.8–67.3) 或 SNP：52.7 (95 %BCI = 36.0–74.8）。使用我们的数据集，我们提供了在对非侵入性样本进行基因分型时对微卫星和 SNP 进行多次重复的重要性的证据，以及对于相同数量的分子标记，微卫星如何在统计上更强大。在小型大型食肉动物种群中观察到的积极趋势需要调整监测方法。常用指标的质量，例如在我们的研究案例中，每年有幼崽的雌性的最低数量，随着种群规模和范围的增加，随着时间的推移可能更难以维持。因此，我们建议实施基于非侵入性 DNA 监测和 SCR 方法的定期监测。