The consequences of reproductive interference in population displacement and mating behavior of invasive Aedes species

Background/Question/Methods

Following its broad diaspora during the last three decades, the Asian Tiger Mosquito  Aedes albopictus has established in new continents and countries where its invaded distribution often overlaps that of the Yellow Fever Mosquito  A. aegypti, which was broadly dispersed from Africa centuries earlier. Many recent invasions by A. albopictus have led to reductions in abundance and range of previously established populations of  A. aegypti. However, despite the potential impacts of such displacements on pathogen transmission by these species, our current understanding of causative mechanisms is poor. A neglected potential mechanism, asymmetric reproductive interference, may contribute to the observed rapid reductions of A. aegypti populations. Recent results from the field showed that  the two species mate at sites of sympatry in Florida and that heterospecific male accessory gland products, transferred during mating,  sterilize A. aegypti, but not A. albopictus, females. Therefore, the potential cost of mating with an A. albopictus male is high for an A. aegypti female, and evolutionary theory predicts avoidance of such behavior to be beneficial.

Results/Conclusions

We demonstrate that  A. aegypti females from populations with a history of contact with A. albopictus in the field in Florida, where the two species have co-existed in sympatry for > 20 years, are, indeed, less likely to mate with interspecific males than females of allopatric origin, suggesting that the selection pressure from reproductive interference (aka satyrization) is strong enough to create mating avoidance mechanisms in A. aegypti females. By selecting for the rapid evolution of this trait in laboratory-based cage experiments, we were, furthermore, able to investigate whether the reduction in incidence of interspecific mating affects intraspecific mating behavior. We show that females from populations that have developed resistance to satyrization, in turn, mate less readily with males of their own species.  Therefore, the development of mechanisms in female A. aegypti to counteract satyrization, may have a cost for mating behavior towards conspecifics.