Aedes albopictus, an invasive species from Asia, is now the most dominant container species in the southeastern United States and has been found to be a strong competitor against many resident mosquitoes. In many parts of the United States, Aedes albopictus interacts with species in the genus of Culex, including the native species Culex restuans. Past work has shown that Aedes and Culex mosquitoes show difference in feeding behavior, with Culex mosquitoes filtering the water column at the surface, whereas Aedes mosquitoes browse at the bottom of containers or on surfaces. We hypothesized that these differences may translate to differences in performance depending on detritus type. We tested this hypothesis in the laboratory by growing larval A. albopictus and C. restuans larvae in ratios of two common detritus types in containers (plant and animal detritus). We used 6 combinations of dried Drosophila melanogaster (animal detritus) and dried maple (leaf detritus). Detritus amounts used included low (0.05 g), medium (0.10 g), and high (0.50 g). Ratios consisted of low animal:low leaf, low animal:high leaf, low animal:no leaf, no animal:low leaf, no animal:high leaf, and medium animal:no leaf. Into each container we added 10 first instar larvae of either C. restuans or A. albopictus. Survival and development time were recorded for males and females for 34 days. Because feeding behaviors differ between these genera, we also investigated the contributions of detritus treatments to adult biomass of both species by using stable isotope techniques.
Results/Conclusions
For Culex restuans, both male and female development time varied significantly among ratios, with the high plant only treatment producing longer development times compared to treatments containing animal detritus. Mass of females and males also was lower in high leaf environments compared to other ratios. Male mass was highest in high animal treatments, with mixed ratios being intermediate. Survival of C. restuans among ratios did not vary significantly. For Aedes albopictus, female development time varied significantly among treatments, with mixed detritus amounts producing shorter development times compared to animal or leaf only treatments. Our findings suggest that the response of each species to detritus ratios was different, with C. restuans males and females performing worse under more detritus ratios compared to A. albopictus. These results are consistent with known differences in performance under single detritus types, and suggest a more robust understanding of the performance of these species under natural food environments.