Timing is key: How pea aphid populations change with warming at different times of day

Despite the extensive work showing temperature effects on insect life history traits, temperature effects at different times of the day are rarely studied.  This could be particularly important as historical data shows temperature increasing more rapidly over night than during the day.  Changing when warming occurs could play a significant role in understanding how a species will respond to temperature changes.  We examined changes in life history traits of the pea aphid, Acyrthosiphon pisum, with respect to warming at different times of the day.  Aphids experienced three different treatments in climate controlled growth chambers: a control (16:8 L:D, 22C day: 17C night) , day warming (+3C for 8h during day), and night warming (+3C for 8h during night).  Each warming treatment exposed aphids to the same magnitude and length of warming but changed when that warming occurred.  Our research showed that warming at night had a greater positive effect on pea aphids than warming during the day.  In general, pea aphid populations under warming treatments grew faster than the control; however, night warming had an even greater effect than warming during the day.  This effect, while only one part of changing temperature trends, could improve our understanding of future temperature effects on different insect species and further indicate the need for considering the daily pattern of warming.