Siyang Xia

and 7 more

Adaptations to anthropogenic domestic habitats contribute to the success of mosquito Aedes aegypti as a major global vector of several arboviral diseases. The species inhabited African forests before expanding into domestic habitats and spreading to the rest of the world. Despite a well-studied evolutionary history, how this species initially moved into human settlements in Africa remains unclear. During this initial habitat transition, Ae. aegypti switched from using natural containers like tree holes as larval breeding sites to using artificial containers like clay pots. Little is known about how these natural versus artificial containers differ in their environments, or whether Ae. aegypti in forest versus domestic habitats evolved any corresponding incipient behavioral divergence, such as in oviposition. To address these gaps, we first characterized physical characteristics, larval density, microbial density, bacterial composition, and volatile profiles of natural versus artificial containers used as mosquito larval breeding sites. We focused on two localities in Africa, La Lopé, Gabon and Rabai, Kenya. In both localities, our data showed that the two habitat-specific container types had significantly different characteristics. We then examined whether such containers differed in their attractiveness for oviposition, a key behavior affecting larval distribution. Forest Ae. aegypti readily accepted artificial containers in our field experiments, and laboratory choice experiments did not find distinct oviposition preference between forest and village Ae. aegypti colonies. These results suggested that African Ae. aegypti were likely generalists in their oviposition site choice. This flexibility to accept different containers might play a vital role during the initial domestication of Ae. aegypti, allowing the mosquitoes to use human-stored water as fallback breeding sites during dry seasons. Although ovipositional changes were not present initially, after longer domestic habitat breeding, the mosquitoes did evolve divergence oviposition preference, as suggested by previous comparisons of African Ae. aegypti and human-specialized non-African Ae. aegypti.

Siyang Xia

and 7 more

The theory of ecological divergence provides a useful framework to understand the adaptation of many species to anthropogenic (‘domestic’) habitats. The mosquito Aedes aegypti, a global vector of several arboviral diseases, presents an excellent study system. Ae. aegypti originated in African forests, but the populations that invaded other continents have specialized in domestic habitats. In its African native range, the species can be found in both forest and domestic habitats like villages. A crucial behavioral change between mosquitoes living in different habitats is their oviposition choices. Forest Ae. aegypti lay eggs in natural water containers like tree holes, while their domestic counterparts heavily rely on artificial containers such as plastic buckets. These habitat-specific containers likely have different environmental conditions, which could drive the incipient divergent evolution of oviposition in African Ae. aegypti. To examine this hypothesis, we conducted field research in two African locations, La Lopé, Gabon and Rabai, Kenya, where Ae. aegypti live in both forests and nearby villages. We first characterized a series of environmental conditions of natural oviposition sites, including physical characteristics, microbial density, bacterial composition, and volatile profiles. Our data showed that in both locations, environmental conditions of oviposition sites did differ between habitats. To examine potential behavioral divergence, we then conducted field and laboratory oviposition choice experiments to compare the oviposition preference of forest and village mosquitoes. The field experiment suggested that forest mosquitoes readily accepted artificial containers. In laboratory oviposition assays, forest and village mosquito colonies did not show a differential preference towards several conditions that featured forest versus village oviposition sites. Collectively, there is little evidence from our study that environmental differences lead to strong and easily measurable divergence in oviposition behavior between Ae. aegypti that occupy nearby forest and domestic habitats within Africa, despite clear divergence between African and non-African Ae. aegypti.