Original Contribution to Theoretical Population Genetics: Modelling Genetic Drift and Bottleneck Effects in Small Ethnic Minority Populations of the Niger Delta

Genetic drift and population bottlenecks have disproportionate effects on small, geographically isolated populations, reducing genetic diversity and elevating the frequency of rare deleterious alleles. The Niger Delta region of South South Nigeria harbours numerous small ethnic minority groups, including the Kula, Ogoni, Kalabari, and Nkoroo, many of whom have experienced historical and contemporary population contractions due to environmental displacement and socioeconomic marginalisation. The population genetics of these groups is entirely uncharacterised. This dissertation makes an original theoretical and empirical contribution to understanding genetic drift and bottleneck effects in Niger Delta ethnic minority populations. The theoretical component develops a novel stochastic simulation model (NigerDeltaSim) that incorporates oil spill-induced displacement, endogamy rates, and seasonal migration patterns as demographic parameters driving genetic drift. The empirical component generated genome-wide SNP data from 350 individuals across six ethnic minority groups using the H3Africa array. Demographic history reconstruction using MSMC, linkage disequilibrium decay analysis, and runs of homozygosity (ROH) analysis were applied. Extreme ROH burden was documented in two of the six groups, consistent with severe recent bottlenecks. Elevated frequencies of population-specific rare variants were correlated with ROH burden. The NigerDeltaSim model accurately recapitulated observed demographic signatures. This theoretical framework advances population genetics modelling for environmental displacement contexts. Keywords: genetic drift, bottleneck, Niger Delta minorities, theoretical population genetics, NigerDeltaSim