Effects of temperature and resource level on host traits and susceptibility to sylvatic dengue virus in a wild and laboratory population of Aedes aegypti mosquitoes

Background/Question/Methods

Understanding how species respond to stresses like competition and changing environmental conditions is a complex issue at the core of ecology. One aspect of this complexity is phenotypic plasticity, or how genetics and the environment may interact to produce different adaptive phenotypes under different environmental conditions.  Predicting whether these new phenotypes can potentially change population and community processes is critically important in a world with changing climate and other disturbances.  Understanding the impacts of phenotypic plasticity under environmental stressors is particularly critical for disease vectors, whose ability to be infected with and transmit pathogens likely depend on the outcome of such plasticity.  

We focused our attention on potential differences in transmission of dengue virus due to phenotypic plasticity in Aedes aegypti, the major vector of this pandemic virus. We conducted a factorial experiment that crossed levels of temperature, resources, and mosquito population (a field-derived (wild-type) or a colonized laboratory population) on larval rearing environment.  After emergence, adult females were kept at the same temperature and given the opportunity to feed on blood containing a sylvatic strain of dengue virus.  We assessed potential changes in mosquito development time, survival, adult size, feeding behavior, and the likelihood of infection.

Results/Conclusions

We found population of origin, temperature, and resource level and their interactions often influence mosquito development times with warmer temperatures and higher resources shortening developmental time in both populations, though the wild population took longer to develop.  Survival to emergence showed differences by population and resource level with the wild type experiencing lower survival along with the lower resource individuals.  Proportion of females feeding and proportion infected show complex patterns with the two populations showing divergent responses influenced by resource and temperature.  A key finding is that lower resource level by itself increased an individual’s probability of being infected by dengue virus in the laboratory population, but only showed an effect when coupled with temperature in the wild one.  Collectively, these results suggest environmental conditions can alter disease transmission probabilities by shifting host traits and that the interactions can be very complex and population dependent.