Introduction

Tropical forests harbour the most diverse plant communities on Earth. This high diversity makes it particularly challenging to understand and predict how these communities will be altered by changing climatic conditions. However, doing so is imperative since, like other systems, tropical forests have experienced and are predicted to experience increases in CO2 and temperature, as well as large shifts in precipitation patterns (Bawa & Markham 1995; IPCC 2007; Malhi & Phillips 2004). Nonetheless, studies of how tropical species will respond to climate change are scarce (e.g. Colwell et al. 2008; Miles, Grainger & Phillips 2004).

One of the main consequences of global climate change projected for the tropics is shifts in rainfall patterns (Hulme & Viner 1998). Models have predicted changes in annual rainfall up to 3000 mm per year, and changes in dry season length of up to several months in the tropics (Cox et al. 2000; Hulme & Viner 1998; Neelin et al. 2006). Projections differ hugely among tropical regions, and both increases and decreases are expected (Hulme & Viner 1998; IPCC 2007; Neelin et al. 2006). Global climate models are converging on projecting significant decreases in mean rainfall in Central and South America, while increases are expected in tropical Africa and Southeast Asia, although considerable uncertainty in rainfall projections still exists (IPCC 2007). Increases in extreme weather events (e.g. droughts, intense precipitation) are also expected in tropical regions (IPCC 2007). Increased frequency of El Niño events (Timmermann et al. 1999) would also affect rainfall patterns in the tropics, since El Niño is associated with extreme climatic events including drought and flooding. At regional scales, changes in climate are also likely to result from land-use change, with large-scale deforestation and habitat fragmentation leading to drier conditions (Costa & Foley 2000; Hoffmann, Schroeder & Jackson 2003; Malhi et al. 2008).