Evolutionary Origins and Phylogenomics of the Nigerian Forest Chameleon (Trioceros wiedersheimi) and Related West African Montane Chameleons

This dissertation provides an original phylogenomic analysis of the Nigerian forest chameleon Trioceros wiedersheimi and related West African montane chameleons, reconstructing evolutionary origins, divergence history, and the geographic drivers of speciation in this poorly known group. Nigeria's montane forests on the Mambilla Plateau and Obudu Cattle Ranch host populations of chameleons that are morphologically and genetically distinct from Cameroon populations, yet taxonomic boundaries and evolutionary relationships remain unresolved, preventing accurate conservation assessment. The dissertation employs genome-wide SNP data from restriction-site associated DNA sequencing (RADseq) on 95 individuals from 14 localities across Nigeria and Cameroon, combined with mitochondrial genome sequencing. Divergence dating using calibrated Bayesian molecular clocks was conducted with BEAST2. Comparative climatic niche modelling using MaxEnt reconstructed historical habitat suitability through LGM, mid-Holocene, and present conditions. Species delimitation analyses using integrative taxonomy (morphometrics, molecular, ecological) were applied. Results support the recognition of at least three distinct evolutionarily significant units within the T. wiedersheimi complex in Nigeria, with inter-unit divergences exceeding 4 percent cytochrome b sequence divergence and 25 percent genome-wide FST. Pleistocene climate oscillations were identified as the primary driver of population isolation and incipient speciation. The dissertation proposes formal taxonomic revisions, provides IUCN Red List data necessary for Nigerian chameleon species assessments, and establishes a phylogenomic reference framework for West African Trioceros systematics. Keywords: phylogenomics, Trioceros wiedersheimi, chameleon, West African montane forests, speciation.