Mosquito responses to trait- and density-mediated interactions of predation

Mosquito and predatory larvae often share the same habitat. Predators may influence mosquito prey populations through both lethal effect and non-lethal pathways. A series of experimental manipulations were used to distinguish between lethal (density-mediated interaction) and non-lethal (trait-mediated interaction) effects in a model system comprised of invasive prey mosquito, Aedes aegypti, and a predatory mosquito Toxorhynchites rutilus. Treatments with predators present or manipulations mimicking daily mortality (density reduction) reduced developmental time and recruitment to the adult stage. Daily records of adult survival of A. aegypti showed that exposure to predators during the juvenile stage shortened the lifespan of adults. This was also observed in treatments, where A. aegypti were replaced at the rate of consumption by T. rutilus. In contrast, numerical reductions in A. aegypti that mimicked daily rate of predation led to adults with the longest lifespan. These observations suggest strong effects of density and trait-mediated interactions in the influence of predators on mosquito biology relevant to their ability to transmit pathogens. These results have potentially important implications for disease control strategies. The primary approach to reduce risk of mosquito-borne diseases is through population reduction of the vectors. We show an unanticipated benefit of biological control by predation for the control of juvenile stages of mosquitoes. Specifically, mosquitoes that are exposed to predators but survive to adulthood will have compromised life expectancy, a key parameter in determining risk of disease transmission.