Divergence of the mosquitoes

Mosquitoes responsible for spreading malaria in sub-Saharan Africa are evolving into two separate species say scientists who have just sequenced the genomes of two strains of the Anopheles gambiae mosquito

Sub-Saharan mosquitoes evolving into two separate species

M and S strains of the Anopheles gambiae mosquito appear physically identical, but researchers from Imperial College London who sequenced their genome found they are genetically very different. These differences are scattered around the entire genome, and are so great that they appear to be becoming different species.

“From our studies we can see that mosquitoes are evolving more quickly than we thought,” said lead researcher Dr Mara Lawniczak, “Unfortunately, strategies that might work against one strain of mosquito might not be effective against another.”

The research suggests that these differing genetic regions between the M and S genomes are likely to affect the mosquito’s development, feeding behaviour and reproduction. Lawniczak says it is important to identify and monitor these hidden genetic changes in order to succeed in controlling malaria.

A second study – the first to use a high density genotyping array – looked at individual mosquitoes from each strain, as well as another strain called Bamako, to see how they are evolving. They compared 400,000 different points in their genomes where variation had been identified, and concluded that the strains appear to be evolving differently – probably in response to environment-specific factors like larval habitats, pathogens and predators.

Imperial researchers are now conducting genome-wide association studies of mosquitoes – using a specially designed chip they used in their second study – to explore which variations in mosquito genes affect their tendency to become infected with malaria and other pathogens.

“We know that the best way to reduce the number of people who contract malaria is to control the mosquitoes that carry the disease,” said lead researcher Professor George Christophides, “It’s important to identify and monitor these hidden genetic changes in mosquitoes if we are to succeed in bringing malaria under control by targeting mosquitoes.”