Researchers from LSTM have exploited a natural experiment created by insecticidal pressure to determine how the most important malaria vectors - A. gambiae s.s. and A. coluzzii respond rapidly to environmental change.
Working with genome analysis specialists from the Wellcome Trust Sanger Institute and field entomologists in Ghana, LSTM researchers sequenced the genomes of individual wild mosquitoes of each species from southern Ghana. The results, published in Nature Communications, reveal that transfer of a major insecticide resistance mutation (kdr) resulted in replacement of over 3 million surrounding DNA bases (1.5% of the genome) of A. coluzzii, with that of A. gambiae s.s. This is especially significant because the two species are very closely related and the region replaced is one of relatively few areas of their genomes that are substantially different. Surprisingly, this apparently huge genomic disruption has had no detectable impact on reproductive isolation with hybridisation rates between the species in Ghana remaining low and stable despite a dramatic rise in frequency of the kdr mutation in A. coluzzii.
Dr David Weetman, co-first author and LSTM Lecturer in Population Genomics, said: "Our work demonstrates amazing flexibility in the genomes of closely related species. The genomic section replaced is not only huge but was previously considered a major 'speciation island'; a probable location for genes driving reproductive isolation between the species. The findings not only call into question the general importance of 'speciation islands', but also importantly show that these closely-related mosquito species, can evolve largely separately but then interchange genetic variation to allow rapid adaptation to human-driven environmental changes.".
The two species, which co-occur throughout much of West and Central Africa, exhibit behavioural and ecological differences. Anopheles c
|Contact: Clare Bebb|
Liverpool School of Tropical Medicine