Species richness is greatest in the tropics, and much of this diversity is concentrated in mountains. Janzen proposed that reduced seasonal temperature variation selects for narrower thermal tolerances and limited dispersal along tropical elevation gradients [Janzen DH (1967) Am Nat 101:233–249]. These locally adapted traits should, in turn, promote reproductive isolation and higher speciation rates in tropical mountains compared with temperate ones. Here, we show that tropical and temperate montane stream insects have diverged in thermal tolerance and dispersal capacity, two key traits that are drivers of isolation in montane populations. Tropical species in each of three insect clades have markedly narrower thermal tolerances and lower dispersal than temperate species, resulting in significantly greater population divergence, higher cryptic diversity, higher tropical speciation rates, and greater accumulation of species over time. Our study also indicates that tropical montane species, with narrower thermal tolerance and reduced dispersal ability, will be especially vulnerable to rapid climate change.

热带地区物种丰富度最大，这种多样性大部分集中在山区。Janzen提出减少季节性温度变化的选择是为了沿着热带海拔梯度缩小热容限和限制散布[Janzen DH（1967）Am Nat101：233–249]。与温带地区相比，这些适应当地特点的地区反过来应促进热带山区的生殖隔离和更高的物种形成率。在这里，我们显示热带和温带山地溪流昆虫的热耐受性和分散能力存在差异，这两个主要特征是山地种群隔离的驱动因素。与温带物种相比，三个昆虫进化枝中的每一个的热带物种具有明显更窄的耐热性和较低的扩散性，从而导致种群差异显着更大，隐秘多样性更高，热带物种形成率更高，并且随着时间的推移物种积累更多。我们的研究还表明，具有较差的耐热性和降低的扩散能力的热带山地物种尤其容易受到快速气候变化的影响。