Corlatti Luca
Chair of Wildlife Ecology and Management University of Freiburg Freiburg Germany.
Ecol Evol. 2020 May 26;10(12):6089-6096. doi: 10.1002/ece3.6354. eCollection 2020 Jun.
Investigating the drivers of diet quality is a key issue in wildlife ecology and conservation. Fecal near infrared reflectance spectroscopy (f-NIRS) is widely used to assess dietary quality since it allows for noninvasive, rapid, and low-cost analysis of nutrients. Samples for f-NIRS can be collected and analyzed with or without knowledge of animal identities. While anonymous sampling allows to reduce the costs of individual identification, as it neither requires physical captures nor DNA genotyping, it neglects the potential effects of individual variation. As a consequence, regression models fitted to investigate the drivers of dietary quality may suffer severe issues of pseudoreplication. I investigated the relationship between crude protein and ecological predictors at different time periods to assess the level of individual heterogeneity in diet quality of 22 marked chamois monitored over 2 years. Models with and without individual grouping effect were fitted to simulate identifiable and anonymous fecal sampling, and model estimates were compared to evaluate the consequences of anonymizing data collection and analysis. The variance explained by the individual random effect and the value of diet repeatability varied with seasons and peaked in winter. Despite the occurrence of individual variation in dietary quality, ecological parameter estimates under identifiable or anonymous sampling were consistently similar. This study suggests that anonymous fecal sampling may provide robust estimates of the relationship between dietary quality and ecological correlates. However, since the level of individual heterogeneity in dietary quality may vary with species- or study-specific features, inconsequential pseudoreplication should not be assumed in other taxa. When individual differences are known to be inconsequential, anonymous sampling allows to optimize the trade-off between sampling intensity and representativeness. When pseudoreplication is consequential, however, no conclusive remedy exists to effectively resolve nonindependence.
研究饮食质量的驱动因素是野生动物生态学和保护领域的一个关键问题。粪便近红外反射光谱法（f-NIRS）被广泛用于评估饮食质量，因为它能够对营养成分进行非侵入性、快速且低成本的分析。f-NIRS的样本可以在知晓或不知晓动物个体身份的情况下进行采集和分析。虽然匿名采样可以降低个体识别成本，因为它既不需要实际捕获动物，也不需要进行DNA基因分型，但它忽略了个体差异的潜在影响。因此，用于研究饮食质量驱动因素的回归模型可能会面临严重的伪重复问题。我研究了不同时间段内粗蛋白与生态预测因子之间的关系，以评估22只被标记的岩羚羊在两年内饮食质量的个体异质性水平。分别拟合了具有和不具有个体分组效应的模型，以模拟可识别和匿名的粪便采样，并比较模型估计值，以评估数据收集和分析匿名化的后果。个体随机效应解释的方差以及饮食重复性的值随季节变化，在冬季达到峰值。尽管饮食质量存在个体差异，但可识别或匿名采样下的生态参数估计始终相似。这项研究表明，匿名粪便采样可能为饮食质量与生态相关因素之间的关系提供可靠的估计。然而，由于饮食质量的个体异质性水平可能因物种或研究特定特征而异，因此不应在其他分类群中假设存在无关紧要的伪重复。当已知个体差异无关紧要时，匿名采样可以优化采样强度和代表性之间的权衡。然而，当伪重复很重要时，不存在有效的解决非独立性的决定性补救措施。
