Global genetic diversity ofAedes aegypti

Abstract

Mosquitoes, especially Aedes aegypti, are becoming important models for studying invasion biology. We characterized genetic variation at 12 microsatellite loci in 79 populations of Ae. aegypti, from 30 countries in six continents and used them to infer historical and modern patterns of invasion. Our results support the two subspecies Ae. aegypti formosus and Ae. aegypti aegypti as genetically distinct units. Ae. aegypti aegypti populations outside Africa are derived from ancestral African populations and are monophyletic. The two subspecies co-occur in both East Africa (Kenya) and West Africa (Senegal). In rural/forest settings (Rabai District of Kenya) the two subspecies remain genetically distinct whereas in urban settings they introgress freely. Populations outside Africa are highly genetically structured likely due to a combination of recent founder effects, discrete discontinuous habitats, and low migration rates. Ancestral populations in sub-Saharan Africa are less genetically structured, as are the populations in Asia. Introduction of Ae. aegypti to the New World coinciding with trans-Atlantic shipping in the 16th to 18th Centuries was followed by its introduction to Asia in the late 19th Century from the New World or from now extinct populations in the Mediterranean Basin. Aedes mascarensis is a genetically distinct sister species to Ae. aegypti s.l.. This study provides a reference database of genetic diversity that can be used to determine the likely origin of new introductions that occur regularly for this invasive species. The genetic uniqueness of many populations and regions has important implications for attempts to control Ae. aegypti, especially for methods using genetic modification of populations.

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).…”

“…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].…”

“…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). Additional introductions of Aaa from the Mediterranean region may also have contributed to the colonisation of Asia by this subspecies [4,118,122,123]. While both the virus and its vector were successfully introduced to the Americas during the slave trade, this was not the case upon the importation of Aaa into Asia.…”

“…aegypti populations are found in Asia, America, Africa, Oceania, the Eastern Mediterranean and the Red Sea coasts. In Africa, populations mainly correspond to the Aaf subspecies [120,[124][125][126] and the presence of Aaa was only reported in some coastal areas in West and East Africa (Senegal and Kenya) [118,120]. This could result from a secondary introduction from the Americas through shipping or from the preservation of a replicate form from the parent, Aaa [117,118].…”

“…aegypti aegypti was virtually eradicated during the 1940s-1970s but completely reinfested the region from both the south of the continent and the Caribbean, where residual mosquito populations subsisted [118,[124][125][126]. During the 'eradication' period of Aaa in South America, YFV could only circulate in sylvatic mosquito species, mostly from the Haemagogus and Sabethes genera (see subsection "In Southern America").…”