Highs and lows: does diel temperature variation matter to aphids?

Insects are greatly affected by the temperature of their environment. Laboratory-based ecological studies on insects commonly rely on incubation chambers or thermostats to maintain a relatively constant temperature, both for rearing the insects and for conducting the experiments. However, nature is far less stable, and temperatures outdoors change over the course of a day, warming during the daylight hours and cooling overnight. Do these daily temperature changes create any significant effects compared to a constant temperature? To answer that question, we reared populations of pea aphids on fava bean plants at 4 different temperature regimes: 16^oC constant, 20^oC constant, 24^oC constant, and 12 hours at 16^oC/12 hours at 24^oC. After 9 days, the new aphid population was counted to measure population growth. The three constant-temperature treatments were used to create a linear model of aphid response to temperature, and the 16^oC/24^oC treatment was compared to the model prediction at its mean temperature of 20^oC. We found that the 16^oC/24^oC treatment resulted in a population that was not significantly different from that predicted by the model. This suggests that using constant temperatures in laboratory-based ecological studies with insects can result in comparable population dynamics to a population subjected to moderate temperature variability throughout a day. These results can be useful in informing methodologies for subsequent study of temperature effects on insects and serve as a useful starting point for studying the role of diel temperature variation on insect ecology.