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

Abstract

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.

Tiger on the prowl: Invasion history and spatio-temporal genetic structure of the Asian tiger mosquito Aedes albopictus (Skuse 1894) in the Indo-Pacific

“…Recently, approximate Bayesian computation (ABC) analysis has proven a powerful tool in testing the probability of competing invasion scenarios. This can provide us with crucial information regarding the timing and origin of mosquito introductions, which has been used recently for Aedes mosquitoes [20–22]. …”

What Does the Future Hold for Yellow Fever Virus? (I)

“…It was first suggested that Aaa had been repeatedly exported to the Americas during the slave trade [4]. This was then confirmed through several genetic analyses performed using either nuclear or mitochondrial markers and microsatellite loci [117][118][119]121]. Genetic analyses also indicate that the New World may have been the source for the introduction of Aaa into Asia, where the subspecies landed by the end of the 19 th century and subsequently dispersed throughout urban areas (see Figure 2).…”

“…Taken together with the historical evidence described earlier this is wholly consistent with the concept that the virus was relatively recently introduced into the New World and evolution towards decreased disease severity has not yet reached the levels seen in Africa. Finally, the African origin of the YFV domestic urban vector, Aedes aegypti and the genetic evidence for its introduction to the New World at roughly the same time as the first appearance of YFV in the Americas strongly supports the probability of an "Out of Africa" scenario [117][118][119]148]. …”

“…The allopatric speciation between the Aaa and the Aaf forms of Ae. aegypti most likely occurred as a single subspeciation event around 4,000 years ago, during the severe drying events that accompanied the expansion of the Sahara in the Northern part of Africa [4,[117][118][119]. Multiple domestication events probably allowed the subsequent selection for "domestic" tendencies such as the ability to exploit artificial water storage elements created by humans or that of feeding on humans [120].…”

Zika Virus: What Have We Learnt Since the Start of the Recent Epidemic?

“…et al, 2016;Weger-Lucarelli et al, 2016;Hart et al, 2017) Culex vector competence. To understand so many disparate results, the protocols should be analyzed and compared taking into account several issues that include the virus-vector origin (geographical coherence), and virus and vector past history in the laboratory (number of passages/generations) that made them genetically quite different to the complex wild circulating ones (Berthet et al, 2014;Bennett et al, 2016;Chouin-Carneiro et al, 2016;.…”