Genetic structure of the mosquito Aedes aegypti in local forest and domestic habitats in Gabon and Kenya

Abstract

Background: The 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? Methods: To 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. Results: In 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 (F st) vary across the genome, with a peak of high divergence observed at the third chromosome only in the La Lopé populations. Conclusion: Collectively, 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.

Population genomics in the arboviral vector Aedes aegypti reveals the genomic architecture and evolution of endogenous viral elements

“…The presence of CFAV‐EVE‐3 in mosquitoes from Rabai, Mexico, Polynesia and Asia is consistent with a common origin of these populations, and thus an endogenization event posterior to the out‐of‐Africa colonization. However, in Rabai, mosquitoes with a peridomestic behaviour, closer to that of Aaf mosquitoes, were also identified suggesting mosquitoes from this location are mixed (Xia et al, 2020). We received ethanol‐preserved mosquitoes from Rabai, and thus could not verify the coloration of the body which is the main visible character differentiating Aaa and Aaf.…”

Larval sites of the mosquito Aedes aegypti formosus in forest and domestic habitats in Africa and the potential association with oviposition evolution

“…aegypti in La Lopé and Rabai likely could easily move between forests and villages, as suggested by studies showing little genetic differentiation between forest and village Ae . aegypti populations (Kotsakiozi et al, 2018 ; Paupy et al, 2014 ; Rose et al, 2020 ; Xia et al, 2020 ). However, because this study did not examine fitness or larval productivity directly, we cannot rule out the possibility that larval survival differed in forest and village larval sites, as oviposition preference does not always align with larval survival and development (Refsnider & Janzen, 2010 ).…”

“…We separated indoor and outdoor larval sites to be consistent with previous studies (McBride et al, 2014 ; Petersen, 1977 ), though in this study, Ae. aegypti indoors and outdoors were both Aaf (Xia et al, 2020 ). We also categorized larval sites by whether Ae.…”

“…To fill the knowledge gaps on Aaf larval habitats, in this study, we characterized forest and domestic larval sites in two African localities: La Lopé in Gabon and Rabai in Kenya. Aedes aegypti in both localities are Aaf based on their morphology and genetic variation (Kotsakiozi et al, 2018 ; Xia et al, 2020 ), but can be found in both forest and village environments. In each locality, forest and village populations showed little genetic differentiation (Xia et al, 2020 ), suggesting local habitat expansion instead of external introduction.…”

“…Aedes aegypti in both localities are Aaf based on their morphology and genetic variation (Kotsakiozi et al, 2018 ; Xia et al, 2020 ), but can be found in both forest and village environments. In each locality, forest and village populations showed little genetic differentiation (Xia et al, 2020 ), suggesting local habitat expansion instead of external introduction. While studies going back to the 1970s indicated indoor‐breeding Ae .…”