Variation in diet concentration and bacterial inoculum size in larval habitats shapes the performance of the Asian tiger mosquito, Aedes albopictus.

backgroundEcological niches present unique environmental and biological trademarks such as abiotic conditions, nutrient availability, and trophic interactions that may impact the ecology of living organisms. Female mosquitoes deposit their eggs in aquatic niches with fluctuating diet sources and microbial communities. However, how niche's diet and microbial composition impact mosquito performance (i.e., traits that maximize mosquito fitness) are not well understood. In this study, we focused on the Asian tiger mosquito, Aedes albopictus, one of the most invasive species in the world and a competent vector for human pathogens. To remove any external microbes, Ae. albopictus eggs were surface-sterilized then hatching larvae were exposed to a gradient of bacterial inoculum (i.e., initial microbial load) and diet concentrations while their impact on mosquito performance traits during juvenile development was measured.

resultsOur results showed that Ae. albopictus larvae develop faster and give larger adults when exposed to microbiota in rearing water. However, mosquito performance, up to the adult stage, depends on both bacterial inoculum size and diet concentration in the aquatic habitat. Upon low inoculum size, larvae survived better if the diet was in sufficient amounts whereas a higher inoculum size was associated with optimal larvae survival only in the presence of the lower amount of diet. Inoculum size, and to a lesser extent diet concentration, shaped bacterial community structure and composition of larval-rearing water allowing the identification of bacterial taxa for which their abundance in larvae-rearing water correlated with niche parameters and/or larval traits.

conclusionsOur work demonstrates that both diet concentration and bacterial inoculum size impact mosquito performance possibly by shaping bacterial community structure in the larval habitat, which accounts for a large part of the juvenile's microbiota. Host-microbe interactions influence several mosquito life-history traits, and our work reveals that niche parameters such as inoculum size and diet concentration could have numerous implications on the microbiota assembly and host evolutionary trajectory. This underlies that host-microbe-environment interactions are an important yet overlooked factor of mosquito adaptation to its local environment, with potential future implications for vector control and vector ecology. Video Abstract.