Complex genome evolution in Anopheles coluzzii associated with increased insecticide usage in Mali

Area of Science:

• Population Genetics
• Insecticide Resistance
• Malaria Vector Biology

Background:

• Adaptive introgression allows species to acquire beneficial genetic variations from related species.
• The malaria vector mosquito Anopheles coluzzii in West Africa is a target for control strategies.
• Insecticide resistance, particularly the kdr gene, is a significant challenge in malaria vector control.

Purpose of the Study:

• To investigate a selective sweep on the X chromosome in Anopheles coluzzii.
• To explore the role of adaptive introgression from Anopheles gambiae in conferring new phenotypes.
• To understand the genetic basis of rapid frequency increase in insecticide resistance.

Main Methods:

• Analysis of selective sweep on standing variation.
• Identification of X-linked haplotypes associated with insecticide resistance.
• Genomic analysis of gene interactions and frequency changes in mosquito populations.

Main Results:

• A selective sweep on the X chromosome was identified in Anopheles coluzzii.
• A nearly fixed X-linked haplotype, including CYP9K1 and CPR125 genes, rapidly increased in frequency.
• This event is linked to the introgression of the kdr insecticide resistance gene from Anopheles gambiae.
• A susceptible Anopheles gambiae population (Bamako form) experienced local extinction.

Conclusions:

• Adaptive introgression of the kdr gene has significantly impacted Anopheles coluzzii.
• The combination of introgressed genes and X-linked haplotypes confers a strong selective advantage.
• Intensified insecticide-treated bed net usage likely drove the extinction of susceptible populations.