Abstract
Aedes aegypti is among the best‐studied mosquitoes due to its critical role as a vector of human pathogens and ease of laboratory rearing. Until now, this species was thought to have originated in continental Africa, and subsequently colonized much of the world following the establishment of global trade routes. However, populations of this mosquito on the islands in the southwestern Indian Ocean (SWIO), where the species occurs with its nearest relatives referred to as the Aegypti Group, have received little study. We re‐evaluated the evolutionary history of Ae. aegypti and these relatives, using three data sets: nucleotide sequence data, 18,489 SNPs and 12 microsatellites. We found that: (a) the Aegypti Group diverged 16 MYA (95% HPD: 7–28 MYA) from its nearest African/Asian ancestor; (b) SWIO populations of Ae. aegypti are basal to continental African populations; (c) after diverging 7 MYA (95% HPD: 4–15 MYA) from its nearest formally described relative (Ae. mascarensis), Ae. aegypti moved to continental Africa less than 85,000 years ago, where it recently (<1,000 years ago) split into two recognized subspecies Ae. aegypti formosus and a human commensal, Ae. aegypti aegypti; (d) the Madagascar samples form a clade more distant from all other Ae. aegypti than the named species Ae. mascarensis, implying that Madagascar may harbour a new cryptic species; and (e) there is evidence of introgression between Ae. mascarensis and Ae. aegypti on Réunion, and between the two subspecies elsewhere in the SWIO, a likely consequence of recent introductions of domestic Ae. aegypti aegypti from Asia.
Highlights
The Aedes aegypti mosquito is often considered to be among the most dangerous animal in the world due to its ability to transmit several arboviruses that historically have taken a heavy toll on human health and continue to do so today (Powell, 2016)
As our main focus was on populations in the southwestern Indian Ocean, and because the population structure of African Ae. aegypti has been recently reported from these microsatellites (Gloria-Soria et al, 2016), we report detailed population statistics from microsatellites in our supplement but summarize our descriptive statistics on the microsatellite data set briefly here
Our results suggest that Ae. aegypti s.s. entered Africa less than 85,000 years ago, as the divergence of Europa and continental African populations was younger than 85,000 years across all five approximate Bayesian computation (ABC) analyses (Figure S3; Tables S14 and S15)
Summary
The Aedes aegypti mosquito is often considered to be among the most dangerous animal in the world due to its ability to transmit several arboviruses (yellow fever, dengue, chikungunya and Zika) that historically have taken a heavy toll on human health and continue to do so today (Powell, 2016). While the evolutionary history and genetic diversity of Ae. aegypti s.s. have received substantial study, populations of Ae. aegypti (and close relatives) on the islands east of Africa have received comparatively little attention (Failloux, Vazeille, & Rodhain, 2002; Kotsakiozi, Evans, et al, 2018; Vazeille et al, 2001). In this region of the southwestern Indian Ocean, Ae. aegypti occupies Madagascar and numerous smaller islands between Africa and Madagascar, such. New data from populations on southwestern Indian Ocean islands provide evidence for novel insights
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