Impacts of seasonal variation in desiccation and resource input on interspecific competition between Aedes albopictus and Aedes aegypti

The mosquitoes Aedes albopictus and Aedes aegypti often co-occur as larvae in container communities in southern Florida, despite evidence that Ae. albopictus is a superior resource competitor to Ae. aegypti. Laboratory studies suggest that Ae. aegypti eggs are more desiccation-resistant than Ae. albopictus eggs and that the outcome of competition is reversed by habitat drying. We tested whether seasonal changes in environmental conditions in the field affect the competitive interactions of these species. We exposed seven density combinations of Ae. albopictus and Ae. aegypti eggs to three desiccation environments [ambient with no hatching, ambient with natural hatching, high humidity with no hatching] for two weeks during both the Florida wet season (summer) and dry season (spring). Eggs were then induced to hatch and larvae allowed to compete until emergence as adults. We incorporated seasonal differences in resource input by collecting leaf and animal detritus from proxy containers weekly in each season, and uniformly distributing pooled detritus among experimental containers. Survival to adulthood was significantly greater for both species in the dry season than the wet season. Competition was evident in the wet season, but much reduced in the dry season, and was not affected by the egg environment, suggesting that differential egg mortality between seasons had little effect on this interaction. Significantly more litter accumulated in proxy cups during the dry season than during the wet season, suggesting that greater resource inputs during the dry season may ameliorate effects of resource competition between Ae. albopictus and Ae. aegypti.