Mr Michael Boyle1, Dr Tom Bishop2, Dr Sarah Luke3, Dr Stephen Hardwick1, Miss R. Isolde Lane-Shaw1, Dr Marion Pfeifer4, Dr Michiel Van Breugel5, Prof Theodore Evans6, Dr Arthur Chung7, Prof Robert Ewers1
1Imperial College London, London, United Kingdom, 2University of Liverpool, Liverpool, UK, 3University of Cambridge, Cambridge, UK, 4University of Newcastle, Newcastle, UK, 5Smithsonian Tropical Research Institute, , Panama, 6University of Western Australia, Perth, Australia, 7Sabah Forestry Department, , Malaysia
Logging and habitat conversion create hotter microclimate conditions in tropical landscapes, which represents a powerful form of localised anthropogenic climate change. These novel conditions are thought to directly affect tropical organisms, although empirical evidence is lacking. Here we investigated how interactions between the physiological traits of species and environmental temperature affected communities of ants, a key organism in tropical ecosystems.
We obtained microclimate recordings from 244 sampling points over a period of 3 years across a gradient of forest disturbance in Malaysian Borneo, and assessed the ant community (4,620 individuals) at a subset of 59 sampling points. Live ants were collected from the same areas (2,359 individuals), and subjected to laboratory warming experiments to determine thermal tolerances.
The abundance of ant genera along a gradient of forest disturbance was defined by an interaction between their thermal tolerance and environmental temperature. In warmer habitats genera with high thermal tolerance had increased abundance, and those with low thermal tolerance had decreased abundance. The genus-level changes in abundance scaled up to generate community-level changes, with a 1 °C increase in maximum daily temperature corresponding to an increase of 0.4 °C in community-weighted mean thermal tolerance.
Our results empirically demonstrate that disturbance-induced microclimate change directly influences the abundance of key organisms in tropical landscapes. Forests around the world are being rapidly disturbed and fragmented, leaving novel landscapes characterised by strongly altered microclimates. How these changes may interact with and reinforce the effects of global climate change over longer time scales remains to be seen.
Michael Boyle is a PhD student at Imperial College London and the National University of Singapore. His research focuses on the resilience of functionally important invertebrates to habitat modification in tropical rainforests, with a particular focus on the link between thermal biology and microclimate change.