Data from: Is there a correlation between abundance and environmental suitability derived from ecological niche modelling? A meta-analysis

It is thought that species abundance is correlated with environmental suitability and that environmental variables, scale, and type of model fitting can confound this relationship. We performed a meta-analysis to (i) test whether species abundance is positively correlated with environmental suitability derived from correlative ecological niche models (ENM), (ii) test whether studies encompassing large areas within a species range (>50%) exhibited higher AS correlations than studies encompassing small areas within a species range (<50%), (iii) assess which modelling method provided higher AS correlation, and (iv) compare strength of the AS relationship between studies using only climatic variables and those that used both climatic and other environmental variables to derive suitability. We used correlation coefficients to measure the relationship between abundance and environmental suitability derived from ENM. Each correlation coefficient was considered an effect size in a random-effects multivariate meta-analysis. In all cases we found a significantly positive relationship between abundance and suitability. This relationship was consistent regardless of scale of study, ENM method, or set of variables used to derive suitability. There was no difference in strength of correlation between studies focusing on large or small areas within a species’ range or among ENM methods. Studies using other variables in combination with climate exhibited higher AS correlations than studies using only climatic variables. We conclude that occurrence data can be a reasonable proxy for abundance, especially for vertebrates, and the use of local variables increases the strength of the AS relationship. Use of ENMs can significantly decrease survey costs and allow the study of large-scale abundance patterns using less information. Including only climatic variables in ENM may confound the relationship between abundance and suitability when compared to studies including variables taken locally. However, modelers and conservationists must be aware that high environmental suitability does not always indicate high abundance.学界普遍认为，物种丰度与环境适宜性存在相关关系，而环境变量、研究尺度以及模型拟合类型可能会干扰这一关联。本研究开展元分析（meta-analysis），旨在达成以下四项目标：(i) 检验物种丰度与基于相关性生态位模型（correlative ecological niche models, ENM）推导得到的环境适宜性是否呈正相关；(ii) 检验覆盖物种分布范围>50%面积的研究，其丰度-适宜性（abundance-suitability, AS）相关系数是否高于覆盖<50%面积的研究；(iii) 评估哪种建模方法可得到更高的AS相关系数；(iv) 对比仅使用气候变量，与同时使用气候及其他环境变量推导适宜性的研究之间，AS关联的强度差异。本研究采用相关系数来衡量物种丰度与ENM推导得到的环境适宜性之间的关联，并将每一个相关系数作为随机效应多变量元分析中的效应量。所有分析均显示，物种丰度与环境适宜性之间存在显著的正相关关系，且该关联不受研究尺度、ENM建模方法或用于推导适宜性的变量集的影响。针对物种分布范围内大、小面积区域开展的研究之间，或是不同ENM建模方法之间，相关系数的强度均无显著差异。联合气候与其他环境变量开展的研究，其AS相关系数强度高于仅使用气候变量的研究。本研究结论如下：物种出现数据可作为丰度的合理替代指标，针对脊椎动物类群尤为如此；引入局地环境变量可增强AS关联的强度。利用ENM可显著降低调查成本，且能在更少数据支撑下开展大尺度物种丰度格局研究。与纳入局地环境变量的研究相比，仅在ENM中使用气候变量可能会干扰丰度与适宜性之间的关联。不过，建模人员与保护从业者需注意：较高的环境适宜性并不总能对应更高的物种丰度。