Evolutionary Ecology of Host-Parasite Coevolution in Malaria Vectors (Anopheles gambiae s.l.) and Plasmodium falciparum Across the Ecology Gradient of North West Nigeria: Original Population Genomic Evidence

This dissertation investigates host-parasite coevolutionary dynamics between Anopheles gambiae sensu lato and Plasmodium falciparum across the ecological gradient of North West Nigeria, spanning Kano, Katsina, Sokoto, Kebbi, Zamfara, Jigawa, and Kaduna States, using population genomics to detect co-evolutionary signatures in both host and parasite genomes. Co-evolutionary arms races between malaria vectors and parasites are predicted to leave genome-wide signatures of reciprocal selection, but co-evolutionary genomics at population level has not been conducted for Nigerian malaria systems. Anopheles gambiae s.l. were collected from 28 sites across three ecological zones. Whole-genome pooled sequencing at 15x coverage provided population-level allele frequencies. Genome-wide selection scans identified regions under positive selection associated with immune function, insecticide resistance, and reproductive fitness. Paired Plasmodium falciparum whole-genome sequences from blood stage parasites collected from infected mosquitoes at the same sites provided parasite-side data. Congruence between host and parasite selection signals was tested using cross-species genetic covariance analysis. Significant congruent selection at mosquito immune loci (TEP1, LRIM1, APL1C) and parasite surface antigen genes (PfCSP, PfAMA1) across the ecological gradient provides original evidence for geographically structured reciprocal co-evolutionary selection in the Nigerian system. The dissertation proposes the North West Nigeria Malaria Co-evolution Framework (NWNMCF) integrating ecological, genomic, and epidemiological predictors of co-evolutionary intensity. Keywords: host-parasite coevolution, Anopheles gambiae, Plasmodium falciparum, population genomics, North West Nigeria.