Mosquitoes (Diptera: Culicidae) are globally important organisms with aquatic and terrestrial life stages. In Arctic ecosystems, they are abundant during the summer, and can be pests to humans and other mammals including caribou (Rangifer tarandus). In the spring, mosquito eggs hatch after ice melt, and the immatures develop in freshwater ponds where they are sensitive to thermal and hydrologic conditions. During larval development, populations are also influenced by predation from diving beetles, which might or might not act in a density-dependent fashion. After emergence, female mosquitoes mate and search for a blood meal from a vertebrate host, representing another biotic control on mosquito abundance. We investigate drivers of mosquito population dynamics in Kangerlussuaq, Greenland, in a system with a sole species of mosquito (Aedes nigripes) and few vertebrate hosts, which makes it uniquely possible to measure demographic parameters. To estimate immature density-dependent mortality, we use data from larval count surveys from four years and preliminary data from an experimental enclosure manipulation. We also investigate spatial dynamics of adult abundance using carbon dioxide trap and sweep net data from three years, testing the hypotheses that mosquito abundance and fecundity increases with suitable larval habitat and/or higher abundance of potential blood meals.
Results/Conclusions
Based on surveys of natural heterogeneity in larval abundance, we found strong evidence of density-dependent mortality on immatures, but it was not strong enough to produce overcompensation. Ponds with more larvae initially still had more emerging adults than those that began with fewer larvae. Peak abundance of adult mosquitoes (in the two weeks after emergence) was six-fold greater in 2015 versus 2016. We hypothesize that low adult abundance in 2016 was due to unusually warm spring temperatures that advanced mosquito phenology and dried up a significant proportion of larval habitat before emergence. Across the landscape only about 16% of adult females contained mature eggs (indicating success in obtaining a blood meal), and fecundity was highest near the caribou breeding grounds where there is a high availability of oviposition habitat and potential blood meal sources relative to other parts of the landscape. Overall, our study indicates key drivers of mosquito population dynamics in both aquatic and terrestrial habitats that may fluctuate in importance depending on annual conditions and which range from strongly density-dependent to density-independent.