Species’ geographic ranges are limited by climate and species interactions. Climate is the prevailing explanation for why species live only within narrow elevational ranges in megadiverse biodiverse tropical mountains, but competition can also restrict species’ elevational ranges. We test contrasting predictions of these hypotheses by conducting a global comparative test of birds’ elevational range sizes within 31 montane regions, using more than 4.4 million citizen science records from eBird to define species’ elevational ranges in each region. We find strong support that competition, not climate, is the leading driver of narrow elevational ranges. These results highlight the importance of species interactions in shaping species’ ranges in tropical mountains, Earth’s hottest biodiversity hotspots.

中文翻译：

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种间竞争限制了热带山区鸟类的分布范围

物种的地理范围受到气候和物种相互作用的限制。气候是为什么物种只生活在生物多样性丰富的热带山区狭窄海拔范围内的普遍解释，但竞争也会限制物种的海拔范围。我们通过对 31 个山区内的鸟类海拔范围大小进行全球比较测试来测试这些假设的对比预测，使用来自 eBird 的超过 440 万公民科学记录来定义每个地区的物种海拔范围。我们发现强有力的证据表明，竞争而非气候是狭窄海拔范围的主要驱动力。这些结果突出了物种相互作用对于塑造热带山区物种分布范围的重要性，热带山区是地球上最热的生物多样性热点地区。