Out of the Forest: How the Environment Affects Termite Distributions, Physiology and Contribution to Ecosystem Processes

Woon, Joel ORCID: 0000-0003-2900-266X (2022) Out of the Forest: How the Environment Affects Termite Distributions, Physiology and Contribution to Ecosystem Processes. Doctor of Philosophy thesis, University of Liverpool.

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Abstract

Termites are an extremely important group of soil invertebrates, contributing to a wide range of ecosystem processes including decomposition, ecosystem hydrology and nutrient redistribution. Despite recent demonstrations that environmental factors may drive differences in termite communities and their ecology, there remain large gaps in our knowledge. Our understanding of termite distributions with respect to different environmental conditions is limited. It is thought that termite diversity peaks in tropical forests, however, there have been few formal tests over large spatial scales to confirm this hypothesis. Additionally, there is very little known about termite physiology. How termites are able to live in a breadth of environments with varied conditions is a considerable knowledge gap, we have very little concept of the physiological limits or the physiological performance of termites and how that might change based on environmental conditions. While there have been recent developments understanding how environmental differences influence termite contribution to decomposition, they have primarily focussed on temperature. Which other environmental variables affect termite-mediated decomposition, particularly between environments with similar temperatures, remains relatively unknown. Throughout this thesis I test how changing environmental conditions, over different scales, influence termite biology. In Chapter 2, I test which environmental variables drive differences in termite diversity and estimated biomass globally, using a worldwide database of standardised data, showing that both diversity and biomass are heavily influenced by soil pH and rainfall, and are both largest in tropical rainforests. Using predictive models, I generate the first worldwide prediction of termite diversity and termite biomass, showing that both distributions are predicted to peak in the equatorial tropics. I also provide the first formal demonstration that termites and earthworms, the other globally influential invertebrate decomposer, predominantly operate in completely different regions of the world. In Chapter 3 I test how changing environmental conditions alter termite physiology. It is thought that the Termitidae, the most diverse family of termites, evolved in Central African tropical forest, and have since colonised, and become ecologically dominant in, tropical savannas. Therefore, they have moved from a relatively buffered environment to one with more extreme environmental conditions. I test the critical thermal limits of the most common mound building species along a natural rainfall gradient in Ghana. Species sampled from savanna locations had significantly wider thermal limits, which suggests it has been a mechanism for termites to colonise environments with more extreme environmental conditions. Finally, in Chapter 4, I test how the termite contribution to decomposition changes over an environmental gradient across Africa. I show that, when temperature is relatively similar between environments, rainfall is influential in determining the importance of different decomposer groups. However, across the whole rainfall gradient, which is representative of the majority of the Afrotropics, termites are the dominant decomposer. Overall, the thesis shows that the environment drives a number of patterns in termite biology, including their distributions, physiology, and their contribution to decomposition, and highlights the importance of understanding how environmental factors may currently influence termite biology, so we can predict how a changing environment might alter termite communities.

Item Type:	Thesis (Doctor of Philosophy)
Divisions:	Faculty of Science and Engineering > School of Environmental Sciences
Depositing User:	Symplectic Admin
Date Deposited:	29 Aug 2023 15:33
Last Modified:	29 Aug 2023 15:34
DOI:	10.17638/03170052
Supervisors:	Parr, Catherine Eggleton, Paul Atkinson, David
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3170052