Microgeography, not just latitude, drives climate overlap on mountains from tropical to polar ecosystems

An extension of the climate variability hypothesis is that relatively stable climate, such as that of the tropics, induces distinct thermal bands across elevation that render dispersal over tropical mountains difficult compared to temperate mountains. Yet, ecosystems are not thermally static in space-time, especially at small scales, which might render some mountains greater thermal isolators than others. Here, we provide an extensive investigation of temperature drivers from fine to coarse scales, and demonstrate that the degree of overlap in temperatures at high and low elevations on mountains is driven by more than just absolute mountain height and latitude. We compiled a database of 29 mountains spanning 6 continents to characterize “thermal overlap” by vertically stratified microhabitats, biomes, and owing to seasonal changes in foliage, demonstrating via mixed-effects modeling that micro- and mesogeography more strongly influence thermal overlap than macrogeography. Impressively, ...