title: Population genomics reveals that an anthropophilic population of Aedes aegypti mosquitoes in West Africa recently gave rise to American and Asian populations of this major disease vector.
abstract: The mosquito Aedes aegypti is the main vector of dengue, Zika, chikungunya and yellow fever viruses. This major disease vector is thought to have arisen when the African subspecies Ae. aegypti formosus evolved from being zoophilic and living in forest habitats into a form that specialises on humans and resides near human population centres. The resulting domestic subspecies, Ae. aegypti aegypti, is found throughout the tropics and largely blood-feeds on humans.
  
  
  
  To understand this transition, we have sequenced the exomes of mosquitoes collected from five populations from around the world. We found that Ae. aegypti specimens from an urban population in Senegal in West Africa were more closely related to populations in Mexico and Sri Lanka than they were to a nearby forest population. We estimate that the populations in Senegal and Mexico split just a few hundred years ago, and we found no evidence of Ae. aegypti aegypti mosquitoes migrating back to Africa from elsewhere in the tropics. The out-of-Africa migration was accompanied by a dramatic reduction in effective population size, resulting in a loss of genetic diversity and rare genetic variants.
  
  
  
  We conclude that a domestic population of Ae. aegypti in Senegal and domestic populations on other continents are more closely related to each other than to other African populations. This suggests that an ancestral population of Ae. aegypti evolved to become a human specialist in Africa, giving rise to the subspecies Ae. aegypti aegypti. The descendants of this population are still found in West Africa today, and the rest of the world was colonised when mosquitoes from this population migrated out of Africa. This is the first report of an African population of Ae. aegypti aegypti mosquitoes that is closely related to Asian and American populations. As the two subspecies differ in their ability to vector disease, their existence side by side in West Africa may have important implications for disease transmission.
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA, 94720-3140, USA.|Present Address: Verily Life Sciences, South San Francisco, CA, 94080, USA.
authors.forename: Jacob E
authors.initials: JE
authors.lastname: Crawford
authors.affiliation: Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, UK.|CIBIO/InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, 4485-661, Vairão, Portugal.
authors.forename: Joel M
authors.initials: JM
authors.lastname: Alves
authors.affiliation: Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, UK.
authors.forename: William J
authors.initials: WJ
authors.lastname: Palmer
authors.affiliation: Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, UK.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Day
authors.affiliation: Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA.
authors.forename: Massamba
authors.initials: M
authors.lastname: Sylla
authors.affiliation: ID-FISH Technology, Palo Alto, CA, 94303, USA.
authors.forename: Ranjan
authors.initials: R
authors.lastname: Ramasamy
authors.affiliation: ID-FISH Technology, Palo Alto, CA, 94303, USA.|Department of Zoology, University of Jaffna, Jaffna, Sri Lanka.
authors.forename: Sinnathamby N
authors.initials: SN
authors.lastname: Surendran
authors.affiliation: Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Black
authors.affiliation: Biological and Environmental Sciences and Engineering Division, KAUST, Thuwal, Kingdom of Saudi Arabia.
authors.forename: Arnab
authors.initials: A
authors.lastname: Pain
authors.affiliation: Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, UK. fmj1001@cam.ac.uk.
authors.forename: Francis M
authors.initials: FM
authors.lastname: Jiggins
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000330:Aedes / Q000235:genetics*; D000354:Africa, Western; D000569:Americas; D025041:Animal Migration; D000818:Animals; D001208:Asia; D001483:Base Sequence; D004199:Disease Vectors; D059472:Exome / Q000235:genetics; D014644:Genetic Variation; D005828:Genetics, Population; D049750:Genome, Insect; D023281:Genomics; D006801:Humans; D010802:Phylogeny; D011156:Population Density; D025341:Principal Component Analysis
keywords: Aedes aegypti; Anthropophilic; Arboviral diseases; Dengue virus; Mosquito evolution; Vector-borne diseases; Zika virus