The resilience of tropical forest invertebrates to microclimate change

Tropical forests are key terrestrial biomes in terms of carbon sequestration, water cycle regulation and biodiversity insurance. They are under threat from a host of anthropogenic factors including logging, poaching, cash-cropping and grazing. Climate change is also a major threat to tropical systems, and it is expected that tropical forests will soon experience conditions that have not existed on earth for millions of years. Structural changes brought about by logging and fragmentation also cause changes to local microclimates, so organisms and ecological processes in logged forests may face combined thermal stresses. Invertebrates make up the majority of animal biodiversity in tropical forests and drive many ecological processes. As ectotherms they are also expected to be sensitive to changes to environmental temperature. In this thesis I studied ants across a gradient of habitat disturbance in Sabah, Malaysian Borneo. I found that interactions between environmental temperature and physiology defined the abundance and functional activity of ants in human-modified tropical landscapes. I also found that temperatures in logged forests exceed the functional tolerances of ants, but that intact forests exhibit remarkable buffering capacity against climate warming. Finally, I described a mechanistic pathway outlining how microclimate change, arising because of human disturbance, led to a reduction in ecosystem functioning via correlations between species’ functional ‘response’ and ‘effect’ traits. These findings suggest that tropical forest invertebrates and the functions they perform are already significantly affected by elevated temperatures in the most heavily logged forests and oil palm plantations. This effect is likely to be exacerbated by future climate warming, with potential implications for the ability of logged forests to maintain current levels of biodiversity. Intact forests, however, may be able to buffer against even the most extreme climate change scenarios, and may be unique in their ability to conserve tropical biodiversity in a warmer future.Open Acces