Abstract Large samples and long time series are often needed for effective broad-scale monitoring of status and trends in wild populations. Obtaining those sample sizes can be more feasible when volunteers contribute to the dataset, but volunteer-selected sites are not always representative of a population. Previous work to account for biased site selection has relied on knowledge of covariates to explain differences between site types, but such knowledge is often unavailable. For cases where relevant covariates have not been defined, we used a simulation study to identify the consequences of including non-probabilistically selected sites (NP sites) in addition to sites selected from a probability-based design (P sites), test modeling frameworks that might correct for biases, and evaluate whether those frameworks could allow NP sites to reduce the sampling requirement for P sites and potentially reduce costs of monitoring. We informed the simulation with pilot data from surveys of monarch butterflies and their obligate larval host plant, milkweed. We found strong biases in NP sites versus P sites in density and trends of monarchs and milkweed. Modeling frameworks that accounted for site type with a group effect or that strongly downweighted NP sites successfully produced unbiased estimates. However, sampling more NP sites typically did not improve accuracy or precision, and adding NP sites sometimes required also adding P sites to prevent biases. Further work on novel modeling frameworks would be useful to allow citizen-science data to contribute useful information to conservation.

中文翻译：

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利用公民科学支持统计稳健的监测计划的挑战

摘要 对野生种群的状况和趋势进行有效的大规模监测通常需要大样本和长时间序列。当志愿者为数据集做出贡献时，获得这些样本量可能更可行，但志愿者选择的站点并不总是代表人群。先前解释有偏差的站点选择的工作依赖于协变量的知识来解释站点类型之间的差异，但这些知识通常是不可用的。对于尚未定义相关协变量的情况，我们使用模拟研究来确定除了从基于概率的设计（P 位点）中选择的位点之外还包括非概率选择的位点（NP 位点）的后果，测试建模框架可能会纠正偏见，并评估这些框架是否可以让 NP 站点减少对 P 站点的采样要求，并有可能降低监测成本。我们通过对帝王蝶及其专性幼虫寄主植物马利筋进行调查的试点数据为模拟提供了信息。我们发现 NP 位点与 P 位点在君主和马利筋的密度和趋势方面存在强烈偏差。考虑具有群体效应的站点类型或强烈降低 NP 站点权重的建模框架成功地产生了无偏估计。然而，采样更多 NP 位点通常不会提高准确性或精确度，并且添加 NP 位点有时还需要添加 P 位点以防止偏差。新建模框架的进一步工作将有助于公民科学数据为保护提供有用的信息。