Investigating the resilience of termite communities to selective logging and climatic changes in Malaysian Borneo

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Citation:
Woon, J. Investigating the resilience of termite communities to selective logging and climatic changes in Malaysian Borneo. (Unpublised Masters thesis, Imperial College London, 2016)


Termites are one of the most important species in terms of decomposition of plant material in tropical forests and as such are crucial to nutrient cycling. They are also unable to regulate their own body temperature. As such it is hypothesised that they will be an early casualty of climate change in tropical forests which would have repercussions felt right through the ecosystem. Previous studies at SAFE have shown that the diversity and abundance of termite species drops in selectively logged forests. Here we used artificial humidity experiments and found that termite species more tolerant of higher temperatures and lower humidity were those found in logged forests, whereas more humidity sensitive species were absent. Some species, though, were remarkably resilient; for example, one species was found to persist from primary forest right through to oil palm plantations. Their tolerance to different microclimates depended where they came from: notably individuals from oil palm were more heat resilient than those in primary forests.

Termites are extremely important for tropical forest ecosystems, but there are large decreases in termite abundance and diversity in disturbed forest. This is likely due to changes in microclimatic conditions that occur in selectively logged forests. The thermal adaptation hypothesis states that tropical species should have a constrained thermal tolerance, and that increases in temperature could cause extinctions of these species. Furthermore, due to the stability of the tropics it has been suggested that the thermal tolerance of creatures, particularly small ectotherms, will not be adaptable. Despite termite importance, and their hypothesised susceptibility to climatic changes, termite tolerances to climatic factors have not been studied. Thermal and desiccation tolerances were recorded for various termite genera, and the significance of a number of life history and physiological traits on these tolerances were tested. The thermal tolerance of termites was higher than expected, with desiccation tolerance being fairly low. Hard bodied termites had a higher thermal and desiccation tolerance than soft bodied termites. Mound nesting genera had the lowest thermal tolerance of all the nesting types, with wood nesting genera having the highest. In addition, deadwood feeders from feeding group I had the highest thermal tolerance, which decreased down the humification gradient to soil feeders which had the lowest. The study also showed that one species of termite, Macrotermes gilvus, had phylogenetic variation in its thermal tolerance, with assemblages from oil palm plantations having a significantly higher thermal tolerance than assemblages found in primary forest. The results suggest that the thermal adaptation hypothesis is too simple when predicting distributions of termites, and potentially other small ectotherms. Furthermore, evidence of plasticity in thermal tolerance refutes recent studies that suggest that small ectotherms will not be able to adapt to the changing climate.