Abstract:
BACKGROUND: Mosquito population dynamics are driven by large-scale (e.g. climatological) and small-scale (e.g. ecological) factors. While these factors are known to independently influence mosquito populations, it remains uncertain
how drivers that simultaneously operate under natural conditions interact to influence mosquito populations. We,
therefore, developed a well-controlled outdoor experiment to assess the interactive effects of two ecological drivers,
predation and nutrient availability, on mosquito life history traits under multiple temperature regimes.
METHODS: We conducted a temperature-controlled mesocosm experiment in Kruger National Park, South Africa,
with the yellow fever mosquito, Aedes aegypti. We investigated how larval survival, emergence and development
rates were impacted by the presence of a locally-common invertebrate predator (backswimmers Anisops varia Fieber
(Notonectidae: Hemiptera), nutrient availability (oligotrophic vs eutrophic, refecting field conditions), water temperature, and interactions between each driver.
RESULTS: We observed that the effects of predation and temperature both depended on eutrophication. Predation
caused lower adult emergence in oligotrophic conditions but higher emergence under eutrophic conditions. Higher
temperatures caused faster larval development rates in eutrophic but not oligotrophic conditions.
CONCLUSIONS: Our study shows that ecological bottom-up and top-down drivers strongly and interactively govern
mosquito life history traits for Ae. aegypti populations. Specifcally, we show that eutrophication can inversely affect
predator–prey interactions and mediate the effect of temperature on mosquito survival and development rates.
Hence, our results suggest that nutrient pollution can overrule biological constraints on natural mosquito populations
and highlights the importance of studying multiple factors.
