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 1,007 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，亚马逊地区的鸟类物种丰富度在高地森林中更高，而季节性洪泛森林的物种多样性尤为匮乏。然而，在已发表的学术文献中，多次出现了"季节性洪泛森林鸟类物种丰富度更高"这一易引发误导的分布模式，且该现象始终未被学界察觉。我们提出假说：数字分布地图（digital distribution maps, DDMs）中的假阳性错误（commission errors）是造成这一误导性模式的根源。在亚马逊地区，这类假阳性错误的产生源于：在绘制物种分布时，研究者对广布性物种与狭域生境专性物种采用了差异化的方法学处理流程。本研究共检视了1007种亚马逊鸟类的数字分布地图，并对存在假阳性错误的地图进行了修正。我们生成了两组鸟类物种丰富度分布图：一组基于原始数字分布地图的空间叠加，另一组基于修正后的数字分布地图的空间叠加。最终鉴定出291种存在分布地图错误的鸟类物种。原始数据显示，季节性洪泛森林的鸟类物种丰富度高于高地森林，但该误导性模式在修正后的丰富度分布图中被完全逆转。季节性洪泛森林中出现假阳性错误的概率是其他区域的35倍。本研究得出如下结论：尽管数字分布地图能够精准刻画亚马逊地区单个物种的分布范围，但单个地图中的假阳性错误在叠加后会发生累积，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，仍可继续使用数字分布地图开展物种丰富度制图：(1) 在区域尺度下完成基础地图优化；(2) 仅以狭域分布物种作为制图对象。