Abstract
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.