Proc. R. Soc. B 280, 20131581 (2013)

When considering climate gradients, factors such as elevation and latitude usually spring to mind. For tree-dwelling organisms, however, the greatest climate gradient is vertical (from ground to tree top) — this very steep temperature profile is a strong driver of species organisation in tropical forests.

Brett Scheffers, from the University of Singapore, and co-workers investigate frogs in Philippine and Singaporean rainforests, finding that they tend to shift higher up in the trees as altitude increases to compensate for the cooler temperatures. These results suggest that vertical climate gradients in forests offer the potential for species to compensate for larger-scale climate changes that are driven by altitude and/or latitude, and occupy larger geographical areas.

An interesting implication of this hypothesis is that climate change could 'flatten' the biodiversity in rainforests by pushing tree-dwelling species towards the cooler and wetter ground. Such flattening could affect forest functioning and species survival.