Geographic range shapes influence species richness in global hotspots

The extraordinary richness of species in tropical mountain regions is
often attributed to aggregations of small-ranged species, allowing tight
spatial packing of their ranges. However, the ranges of species in these
regions are also distinctly more patchy and elongated than those found in
adjacent lowlands. Our global analysis of mainland birds demonstrates that
these range shapes augment spatial variation in species richness. Both the
linearity and patchiness of species ranges are most pronounced in
aseasonal and topographically complex regions, most notably in the
tropical Andes, where these range shapes contribute more to the pattern of
species richness than broad-scale variations in range size. Consequently,
niche-based processes that govern the spatial configuration of habitats
contribute to patterns of species richness in global hotspots over and
above the processes that affect species richness through range sizes.

热带山地地区极高的物种丰富度，通常被归因于狭域分布物种（small-ranged species）的聚集，使得其分布范围得以紧密的空间排布。然而，这些区域内的物种种群分布范围，相较于邻近低地的物种分布范围，明显更具斑块性与狭长性。我们针对大陆鸟类开展的全球尺度分析表明，此类分布范围形态会加剧物种丰富度的空间异质性。物种分布范围的狭长性与斑块性，在无季节变化且地形复杂的区域表现最为显著，尤以热带安第斯山脉（Tropical Andes）为甚；在此类区域中，此类分布范围形态对物种丰富度格局的贡献，大于分布范围大小的大尺度变化所带来的影响。因此，支配栖息地空间配置的生态位相关过程，在全球物种丰富度热点区域中，对物种丰富度格局的塑造作用，超出了通过分布范围大小影响物种丰富度的各类过程。