Kroll Andrew J, Garcia Tiffany S, Jones Jay E, Dugger Katie, Murden Blake, Johnson Josh, Peterman Summer, Brintz Ben, Rochelle Michael
Weyerhaeuser, Federal Way, Washington, United States of America.
Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, United States of America.
PLoS One. 2015 Nov 30;10(11):e0142903. doi: 10.1371/journal.pone.0142903. eCollection 2015.
Plethodontid salamanders are diverse and widely distributed taxa and play critical roles in ecosystem processes. Due to salamander use of structurally complex habitats, and because only a portion of a population is available for sampling, evaluation of sampling designs and estimators is critical to provide strong inference about Plethodontid ecology and responses to conservation and management activities. We conducted a simulation study to evaluate the effectiveness of multi-scale and hierarchical single-scale occupancy models in the context of a Before-After Control-Impact (BACI) experimental design with multiple levels of sampling. Also, we fit the hierarchical single-scale model to empirical data collected for Oregon slender and Ensatina salamanders across two years on 66 forest stands in the Cascade Range, Oregon, USA. All models were fit within a Bayesian framework. Estimator precision in both models improved with increasing numbers of primary and secondary sampling units, underscoring the potential gains accrued when adding secondary sampling units. Both models showed evidence of estimator bias at low detection probabilities and low sample sizes; this problem was particularly acute for the multi-scale model. Our results suggested that sufficient sample sizes at both the primary and secondary sampling levels could ameliorate this issue. Empirical data indicated Oregon slender salamander occupancy was associated strongly with the amount of coarse woody debris (posterior mean = 0.74; SD = 0.24); Ensatina occupancy was not associated with amount of coarse woody debris (posterior mean = -0.01; SD = 0.29). Our simulation results indicate that either model is suitable for use in an experimental study of Plethodontid salamanders provided that sample sizes are sufficiently large. However, hierarchical single-scale and multi-scale models describe different processes and estimate different parameters. As a result, we recommend careful consideration of study questions and objectives prior to sampling data and fitting models.
无肺螈科蝾螈是种类多样且分布广泛的分类群，在生态系统过程中发挥着关键作用。由于蝾螈利用结构复杂的栖息地，且只有一部分种群可供采样，因此评估采样设计和估计器对于深入推断无肺螈科生态学以及对保护和管理活动的响应至关重要。我们进行了一项模拟研究，以评估多尺度和分层单尺度占用模型在具有多个采样层次的前后对照影响（BACI）实验设计背景下的有效性。此外，我们将分层单尺度模型应用于美国俄勒冈州喀斯喀特山脉66个林分中，针对俄勒冈细螈和埃氏林螈在两年内收集的实证数据。所有模型均在贝叶斯框架内进行拟合。随着初级和次级采样单元数量的增加，两种模型中的估计器精度均有所提高，这突出了增加次级采样单元时可能获得的收益。两种模型在低检测概率和小样本量时均显示出估计器偏差的迹象；对于多尺度模型，这个问题尤为严重。我们的结果表明，在初级和次级采样水平上有足够的样本量可以缓解这个问题。实证数据表明，俄勒冈细螈的占有率与粗木质残体的数量密切相关（后验均值 = 0.74；标准差 = 0.24）；埃氏林螈的占有率与粗木质残体的数量无关（后验均值 = -0.01；标准差 = 0.29）。我们的模拟结果表明，只要样本量足够大，这两种模型都适用于无肺螈科蝾螈的实验研究。然而，分层单尺度模型和多尺度模型描述的是不同的过程，估计的是不同的参数。因此，我们建议在对数据进行采样和拟合模型之前，仔细考虑研究问题和目标。
