Consumptive and non-consumptive effects of predators on Culex mosquitoes

Background/Question/Methods

Transmission of a vector-borne infectious disease minimally involves interactions among a host, vector, and pathogen, but these three players rarely interact in isolation. Rather, each is embedded within communities of alternate hosts, competitors, and predators. These community-level interactions can strongly impact pathogen prevalence in host populations.  Here, we investigate the role of predators in shaping vectorial capacity of the West Nile virus mosquito vector, Culex pipiens, via non-consumptive channels.  Developing larvae exposed to predation risk may shift resources to predator avoidance. In turn, this shifting resource allocation could have consequences that are manifested in the condition of mosquitoes that evade predation and survive to the adult, transmitting stage.  Changes could include altered longevity, fecundity, or immune function, all of which could ultimately affect vector transmission efficiency and thus disease dynamics.  We choose to focus on longevity, since mosquitoes that live longer could have more opportunities to transmit pathogens.  In field mesocosms, we examined both mosquito survivorship and adult longevity following exposure to bio-diverse communities of aquatic predators. Predators were varied to mimic natural variation in the field, where communities naturally varied in species richness, evenness, and composition

Results/Conclusions

We found that predators significantly lowered survivorship of developing Culex pipiens larvae to the adult stage, although this effect was not clearly impacted by predator biodiversity. Additionally, adults emerging from predator treatments experienced a greater hazard of mortality than those emerging from predator free controls, with a trend toward predator evenness further altering adult longevity.  These findings suggest diverse predator communities might (indirectly) impact disease dynamics both by reducing vector densities, and by producing less-robust vectors.  Ongoing field studies are further examining how predator community structure impacts mosquitoes through both lethal and non-lethal channels.  Finally, field surveys of predator communities across disturbance gradients will put these results into a landscape perspective and could help explain geographic patterns in mosquito abundance and disease prevalence.