Drivers of Diversity and Ecological Impacts of the Termite Communities of the Republic of Congo

Abstract

Termites play a major role in the tropics, acting as decomposers, soil bioturbators, and mound builders as they fundamentally shape ecosystem function. Central Africa is a global hotspot of termite diversity and abundance, yet much remains to learn about the drivers and implications of this diversity. To elucidate how termite communities distribute across and influence the landscape, I combine ground sampling and remote sensing, morphology and genetics, and observational and manipulative studies in the heterogeneous landscape of Odzala-Kokoua National Park (OKNP) in the Republic of the Congo. In Chapter 1, I provide a foundation for the following chapters and future research through widespread sampling and characterization of the termite communities of OKNP, comparing diversity and turnover across habitat types. I find sharp breaks in community composition across ecotones, suggesting the dynamic landscape of this region contributes to its status as a global biodiversity hotspot for termites. I also use termite diversity patterns to support an ancient origin for the savanna patches of OKNP. In Chapter 2, I quantify the landscape of soil sodium availability in OKNP, focusing on a type of sodium-rich forest clearing unique to the western Congo Basin called a ‘bai’. I measure the effects of bai sodium hotspots on termite communities and decomposition rates. This reveals surprising patterns of increasing termite diversity with soil sodicity for the soil-feeding but not wood-feeding termite groups, with no effect of sodium on measured decomposition rates. In Chapter 3, I estimate the biomass of a soil-feeding species in the termite genus Isognathotermes and quantify the spatial patterning of their mounds in the savannas of OKNP. I demonstrate that the Isognathotermes biomass likely outweighs the biomass of more visible Macrotermes colonies, emphasizing the ecological importance of soil-feeder termites in savannas. In Chapter 4, I look for differentially expressed genes in response to thermal stress by comparing a savanna-specialist soil-feeding termite with a forest-specialized soil-feeder. I find that soil-feeding termites present particular challenges to traditional thermal stress and transcriptomic techniques. Together, this research stresses the importance of treating termites as a heterogeneous group when predicting their responses and contributions to landscape change, and highlights the need for greater focus on the abundant but understudied soil-feeding termites.