Modeling Biodiversity-Ecosystem Function Relationships in West African Tropical Forests: Evidence from Nigerian Reserves

The relationship between biodiversity and ecosystem function is a central theoretical question in ecology, with critical implications for conservation policy. While extensive experimental and observational evidence exists for temperate systems, the biodiversity-ecosystem function relationship in West African tropical forest systems remains poorly characterized empirically. This dissertation investigates biodiversity-ecosystem function relationships across a gradient of forest biodiversity in Nigerian reserves spanning three geopolitical zones: Cross River State (South South), Ogun State (South West), and Taraba State (North East). A multi-trophic approach examines the contributions of plant, invertebrate, vertebrate, and microbial diversity to four ecosystem functions: above-ground biomass production, litter decomposition rate, pollination service delivery, and seed dispersal effectiveness. Structural equation modeling is used to test competing theoretical models of biodiversity-ecosystem function relationships, including the complementarity, selection effect, and functional redundancy hypotheses. Results from 240 vegetation plots and associated biodiversity and function measurements across degradation gradients demonstrate significant positive biodiversity-function relationships for all four measured functions, with complementarity effects being most important at high biodiversity levels and functional redundancy providing resilience buffers at intermediate diversity. The dissertation provides the first multi-trophic biodiversity-function dataset from West African tropical forests and contributes novel empirical support for diversity-informed conservation prioritization in Nigerian forests. Keywords: biodiversity, ecosystem function, tropical forests, Nigeria, structural equation modeling