Tropical forest–savanna ecotones are of considerable interest to biologists due to their high habitat heterogeneity (beta diversity), importance in rainforest speciation (Smith et al. 1997), and, for those climatically controlled ecotones, the manner of their response to future climate change (IPCC 2007). Forest–savanna transitions may be governed by any number of factors, including soil type, fire, hydrology, disturbance (both natural and anthropogenic), as well as climate, in particular the seasonality of precipitation (Furley et al. 1992). Determining the underlying control for a forest–savanna transition in a particular location may therefore not be straightforward and may differ markedly among forest–savanna ecotones, even when in relatively close geographic proximity.