# Genomic population structure and insecticide resistance mechanisms in the malaria vector An. coluzzii across contrasting bioclimatic zones in West Africa

## TL;DR

This study explores how environmental factors affect the movement and insecticide resistance of malaria mosquitoes in West Africa.

## Contribution

The study reveals how bioclimatic zones influence gene flow and resistance mechanisms in An. coluzzii mosquitoes.

## Key findings

- Restricted gene flow between northern savannah and southern forest populations of An. coluzzii was identified.
- Insecticide resistance profiles vary across bioclimatic zones in Ghana, reflecting differences in insecticide use.
- Unique resistance mechanisms were observed in the coastal region of Greater Accra due to urban agriculture.

## Abstract

Environmental barriers influencing the movement of insect vectors can govern adaptive gene flow, including the dispersal of insecticide resistance mechanisms that compromise population control. We sought to understand population connectivity of the major malaria vector, An. coluzzii, across the different bioclimatic zones of West Africa using SNPs from whole genomes and inversion karyotypes previously associated with environmental adaptation. We identified restricted gene flow between populations from northern savannah and southern forested regions. Using Ghana as a case study, we found marked differences in insecticide resistance profiles across the different bioclimatic zones suggesting that population connectivity impacts on adaptive allele sharing. Greater evidence for target site pyrethroid and metabolic cross-resistance in the North reflects differences in insecticide use across the country. We also observed distinct resistance mechanisms in the coastal region of Greater Accra which may result from intense urban agricultural activity. Overall, findings suggest that environmental conditions restrict An. coluzzii gene flow to impact the geographical distribution of molecular insecticide resistance.