Density-dependent population dynamics in Aedes aegypti slow the spread of wMel Wolbachia.
Abstract
Field release of endosymbiotic Wolbachia bacteria into wild Aedes aegypti mosquito populations is a promising strategy for biocontrol of dengue. This strategy requires successful Wolbachia invasion through the mosquito vector population. Natural variation in mosquito fitness due to density-dependent competition for limited food resources may influence Wolbachia invasion. We know little about these effects, largely because our understanding of density-dependent dynamics in mosquito populations is limited. We developed an empirical model of A. aegypti-Wolbachia dynamics where food resources available to the developing larvae are limited. We assessed the extent of density-dependent regulation in our A. aegypti population using a Bayesian statistical model that estimates the temporal variation in mosquito fitness components. We monitored the spread of Wolbachia and assessed the effect of the bacteria on larval fitness components. We demonstrate that mosquito population growth is regulated by strong larval density-dependent variation in mosquito fitness components. Wolbachia spread was slowed by this heterogeneity in mosquito fitness, which reduces the capacity of the bacteria to invade. However, we found no evidence that Wolbachia affects larval fitness components. Synthesis and applications. We demonstrate that the extent and form of density-dependent dynamics in the host population can have a major influence on Wolbachia invasion. These findings help explain slow Wolbachia invasion rates and indicate that the success of field release strategies for dengue control can depend on attaining high Wolbachia frequencies in the mosquito population.