Data from: Misuse of bird digital distribution maps creates reversed spatial diversity patterns in the Amazon

It is well known that bird richness in the Amazon is greater in upland forests and that seasonally flooded forest is particularly species poor. However, the misleading pattern of greater bird richness in seasonally flooded forest has emerged seemingly unnoticed numerous times in richness maps in the literature. We hypothesize that commission errors in digital distribution maps (DDMs) are the cause behind the misleading richness pattern. In the Amazon, commission errors are a consequence of the different methodological treatment given to large-ranged versus small-ranged habitat specialists when mapping distributions. DDMs of 1007 Amazonian birds were examined, and maps that had commission errors were corrected. We generated two richness maps, one from the overlay of original DDMs and another from the overlay of the corrected ones. We identified 291 species whose distribution maps had errors. In the original data, seasonally flooded forests showed higher species richness than upland forest, but this pattern was reverted in the corrected richness map. Commission errors were 35 times more likely in the seasonally flooded forest. We conclude that DDMs accurately portray the distribution of single species in the Amazon. Commission errors in individual maps, however, accumulate when they are overlaid, explaining the misleading pattern for birds in the Amazon. DDMs can continue to be used mapping richness, as long as, at a regional scale: (1) basic map refinements are carried, or (2) only small-range species are used for mapping species richness.众所周知，亚马逊地区的鸟类丰富度在高地森林中更高，而季节性泛滥森林的物种丰富度普遍偏低。然而，相关文献的物种丰富度图谱中，多次出现了季节性泛滥森林鸟类丰富度更高的误导性模式，且该现象长期未被学界察觉。我们提出研究假设：数字分布图谱（Digital Distribution Maps, DDMs）中的假阳性误差（commission error）正是催生这一误导性丰富度模式的根源。在亚马逊区域，假阳性误差的产生源于物种分布制图时，对广分布栖息地特化种与窄分布栖息地特化种采用了差异化的方法学处理流程。我们检视了1007种亚马逊鸟类的数字分布图谱，并对存在假阳性误差的图谱进行了修正。我们据此生成了两组物种丰富度图谱：一组基于原始数字分布图谱的叠加结果，另一组基于修正后图谱的叠加结果。经筛查，共有291种鸟类的分布图谱存在假阳性误差。原始数据显示，季节性泛滥森林的物种丰富度高于高地森林，但该模式在修正后的丰富度图谱中完全逆转。季节性泛滥森林中出现假阳性误差的概率是其他区域的35倍。本研究证实，在亚马逊地区，数字分布图谱能够准确呈现单个物种的地理分布范围。但单张图谱中的假阳性误差在叠加过程中会发生累积，这正是亚马逊地区鸟类误导性丰富度模式的成因。只要满足以下任一条件，数字分布图谱仍可用于物种丰富度制图：（1）完成基础的图谱优化工作；（2）仅以窄分布物种为对象开展物种丰富度制图。