Abstract
BackgroundThe mosquito Aedes aegypti is a devastating disease vector transmitting several important human arboviral diseases. In its native range in Africa, the mosquito can be found in both the ancestral forest habitat and anthropogenic habitats such as villages. How do the different habitats impact the population genetic structure of the local mosquito populations?MethodsTo address this question, we simultaneously sampled Ae. aegypti from the forest and local villages in La Lopé, Gabon and Rabai, Kenya. The mosquitoes were genotyped at 12 microsatellite loci and a panel of ~25,000 single nucleotide polymorphisms (SNPs), which allowed us to estimate their genetic ancestries and the population genetic structure related to habitats and sampling sites.ResultsIn the context of the global population genetic structure of Ae. aegypti, clustering analysis showed that mosquitoes from the same locality (La Lopé or Rabai) have similar genetic ancestry, regardless of their habitats. Further analysis at the local scale also found no strong genetic differentiation between the forest and village mosquitoes in both La Lopé and Rabai. Interestingly, these results from our 2017 samples from Rabai, Kenya contrast to the documentation of genetic differentiation between village and forest mosquito collections from 1975–1976 and 2009. Between-habitat measures of genetic difference (Fst) vary across the genome, with a peak of high divergence observed at the third chromosome only in the La Lopé populations.ConclusionCollectively, these results demonstrated that there is little genetic isolation between forest and village habitats, which suggests possible extensive gene flow between them. From an epidemiological perspective, the forest habitat could act as a refuge for mosquitoes against vector control programmes in the domestic settings. Moreover, sylvatic populations could play a role in zoonotic pathogen transferred to humans. Therefore, future studies on disease transmission and vector control planning in the study area should take natural populations into consideration.
Highlights
The mosquito Aedes aegypti is a devastating disease vector transmitting several important human arboviral diseases
Minimal traces of the genetic ancestry differing from the main Ae. aegypti formosus (Aaf) cluster existed in the 2017 Rabai samples, which is the ancestry similar to the Rabai indoor samples from 2009 and 2011 and some Asian-Pacific populations
principal components analysis (PCA) with microsatellite data and single nucleotide polymorphisms (SNPs) data both showed that the 2016 La Lopé samples and the 2017 Rabai samples overlap with the majority of African populations (Additional file 1: Figure S3), which is again consistent with snmf and STRUCTURE analysis results
Summary
The mosquito Aedes aegypti is a devastating disease vector transmitting several important human arboviral diseases. The mosquito has become a major public health concern in tropical and subtropical regions worldwide [5] This mosquito is native to subAfrican forests and invaded domestic habitats before spreading to other continents in the last 400–500 years, likely associated with human movements such as the slave trade [6,7,8,9,10,11,12]. Populations of Ae. aegypti outside of Africa exhibit strong adaptations to the domestic environments, for example, a strong preference for biting humans and breeding in human-made containers [13] These domestic adaptations likely help the mosquitoes to reside permanently around humans, which contributes to their high efficacy as human disease vectors
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