Historical environmental change in Africa drives divergence and admixture of Aedes aegypti mosquitoes: a precursor to successful worldwide colonization?

Author information

Computational Evolutionary Biology Group, Faculty of Life Sciences, University of Manchester, Manchester, UK.
Department of Veterinary Microbiology and Parasitology, Sokoine University of Agriculture, Morogoro, Tanzania.
Walter Reed Biosystematics Unit, Smithsonian Institution Museum Support Center, Suitland, MD, USA.
Walter Reed Army Institute of Research, Silver Spring, MD, USA.
Uniformed Services University of Health Sciences, Bethesda, MD, USA.
Department of Entomology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Department of Arbovirology, Emerging and Re-emerging Infections, Uganda Virus Research Institute, Entebbe, Uganda.
Agro-Eco-Health Platform for West and Central Africa, International Institute of Tropical Agriculture, Cotonou, Republic of Benin.
Entomology Unit, Department of Zoology, University of Ibadan, Ibadan, Nigeria.
Mosquito Research & Control Unit, Cayman Islands Government, Grand Cayman, Cayman Islands.
London School of Hygiene and Tropical Medicine, London, UK.
Medical Entomology Research Division, Department of Medical Research (Lower Myanmar), Ministry of Health, Yangon, Myanmar.
National Institute for Research in Environmental Health, Ministry of H & FW Government of India, Bhopal, India.


Increasing globalization has promoted the spread of exotic species, including disease vectors. Understanding the evolutionary processes involved in such colonizations is both of intrinsic biological interest and important to predict and mitigate future disease risks. The Aedes aegypti mosquito is a major vector of dengue, chikungunya and Zika, the worldwide spread of which has been facilitated by Ae. aegypti’s adaption to human-modified environments. Understanding the evolutionary processes involved in this invasion requires characterization of the genetic make-up of the source population(s). The application of approximate Bayesian computation (ABC) to sequence data from four nuclear and one mitochondrial marker revealed that African populations of Ae. aegypti best fit a demographic model of lineage diversification, historical admixture and recent population structuring. As ancestral Ae. aegypti were dependent on forests, this population history is consistent with the effects of forest fragmentation and expansion driven by Pleistocene climatic change. Alternatively, or additionally, historical human movement across the continent may have facilitated their recent spread and mixing. ABC analysis and haplotype networks support earlier inferences of a single out-of-Africa colonization event, while a cline of decreasing genetic diversity indicates that Ae. aegypti moved first from Africa to the Americas and then to Asia. ABC analysis was unable to verify this colonization route, possibly because the genetic signal of admixture obscures the true colonization pathway. By increasing genetic diversity and forming novel allelic combinations, divergence and historical admixture within Africa could have provided the adaptive potential needed for the successful worldwide spread of Ae. aegypti.




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