Environmental impacts on complex life cycles: Results from mosquitoes response to temperature variation

Background/Question/Methods

For organisms with complex life cycles, individual life stages have evolved specific responses to variation in environmental conditions.  Any carry-over effects of these responses across life stages could confer a transgenerational fitness advantage. In mosquitoes, temperature is known to affect population dynamics although most investigations of response of mosquitoes to temperature have focused on only part of their life cycle (e.g., aquatic phase). This study was carried out to investigate the response of intraspecific larval competition to temperature variation and “carry-over” effects of temperature from larval to adult stages in the mosquito Aedes albopictus. For larval competition, development time, survival and adult mass was measured for 10 replicates of larvae reared in low (10) medium (20) and high (40) densities across 3 temperatures: low (21⁰C), medium (27⁰C) and high (34⁰C), with constant food and photoperiod. For the carry-over effects, adult survival was measured for males and females maintained within adult temperatures of 21, 27 and 34⁰C from the medium larval density at each source temperature (21, 27 and 34⁰C). Fecundity data was also obtained from mated females maintained within the three adult temperatures.

Results/Conclusions

There was a significant interaction between larval density and temperature for development time and adult body mass for males and females. Increasing temperatures led to decreasing larval development times and adult mass, whereas increasing densities led to increasing development times but decreasing adult mass. However, larval survival was not affected by temperature or larval density. In the carry-over effects experiment, a significant interaction was observed between source temperatures and adult temperatures, with the higher adult temperatures leading to greater differences in fecundity and adult survival. Based on these outcomes, it can be concluded that for Aedes albopictus, temperature affects the outcome of larval competition and that adult fitness is influenced by interactions of larval and adult temperatures. Future studies aim to address questions on life stage response of other mosquitoes species and genera to temperature variations and to other environmental factors.