Towards a Theoretical Framework for Predicting Begomovirus-Whitefly-Host Plant Interactions Under Climate Change in Sub-Saharan Africa: A Nigerian Case Study

Begomovirus epidemics driven by the whitefly Bemisia tabaci represent complex tripartite interactions between virus, vector, and host plant, mediated by environmental variables projected to shift significantly under climate change scenarios applicable to sub-Saharan Africa. Existing theoretical models for begomovirus spread have been calibrated primarily on temperate and Mediterranean systems, creating a major applicability gap for West African conditions. This dissertation research develops an original theoretical framework for predicting begomovirus-whitefly-host plant dynamics under projected climate change scenarios, using Nigerian cassava and tomato begomovirus systems as empirical anchors. The framework integrates epidemiological compartmental modelling with landscape-level vector movement simulation, validated against a 15-year retrospective disease incidence dataset from ten Nigerian states. Bayesian parameterisation procedures are used to fit model parameters to empirical data, and sensitivity analyses identify the climate-disease linkage pathways with the greatest predictive leverage. Scenario analyses project begomovirus epidemic risk surfaces for Nigeria under IPCC RCP4.5 and RCP8.5 scenarios through 2050. Key theoretical contributions include original formulations of temperature-dependent vector-acquisition efficiency functions and host susceptibility modifiers under heat stress, both derived from controlled experimental data generated in the first phase of the research programme. The framework is designed for transferability to other begomovirus-whitefly-crop systems in the sub-Saharan context, contributing a generalisable theoretical architecture to the plant virology and plant epidemiology literature. Keywords: begomovirus, Bemisia tabaci, theoretical framework, climate change, Nigeria.