Tropical mountain passes are out of reach – but not for arboreal species

According to a prevailing hypothesis, lowland tropical organisms are unlikely to successfully cross mountain passes because they have neither acclimated nor adapted to the colder temperatures found at higher elevations. However, this expectation assumes that changes in temperature are uniform across space and fails to account for the presence of diverse microclimates created by structurally complex ecosystems, such as rainforests. We collected and analyzed temperature data from Afrotropical, Indomalayan, and Australasian tropical mountain ecosystems to determine the degree of overlap between lowland and upland “thermal regimes” in three selected microenvironments. The thermal regimes of upland and lowland forest canopies overlapped to a greater extent than the thermal regimes of upland and lowland soils or ground-level sites. Tree-dwelling animals may therefore be able to bypass temperature constraints imposed by geography by virtue of where they live, which could lead to broader distributions and greater resilience to climatic change and variability as compared with ground-dwelling species.