Assessing the impacts of endosymbionts on laboratory Aedes albopictus populations

Wolbachia pipientis is an intracellular α-proteobacteria that occurs naturally in the mosquito Aedes albopictus. Wolbachia infections have shown to impart both positive and negative effects to hosts in terms of immature development, survival and reproduction. Here an experimental model system is used to test (1) the sustainability of closed laboratory populations of Aedes albopictus and (2) investigate the population-level effects of Wolbachia infection. The model system utilizes a dual cage design, with one cage assigned for immature rearing and another for adult populations. Replicate populations of infected and aposymbiotic Ae. albopictus were maintained and monitored for 720 days. Both infected and aposymbiotic populations reached stable population sizes within the experimental model system. Population sizes for aposymbiotic cages were significantly higher at equilibrium than that of infected cages. Mean sex ratio of infected populations were close to 1:1, while aposymbiotic populations were female-biased. Death rates and fecundity in infected populations were higher than aposymbiotic populations. Our results offer evidence for general fitness effects that could in part explain the widespread persistence of Wolbachia in natural populations of Ae. albopictus .