title: Daily temperature extremes play an important role in predicting thermal effects.
abstract: Organisms in natural environments experience diel temperature fluctuations, including sporadic extreme conditions, rather than constant temperatures. Studies based mainly on model organisms have tended to focus on responses to average temperatures or short-term heat stress, which overlooks the potential impact of daily fluctuations, including stressful daytime periods and milder night-time periods. Here, we focus on daily maximum temperatures, while holding night-time temperatures constant, to specifically investigate the effects of high temperature on demographic parameters and fitness in the English grain aphid Sitobion avenae. We then compared the observed effects of different daily maximum temperatures with predictions from constant temperature-performance expectations. Moderate daily maximum temperatures depressed aphid performance while extreme conditions had dramatic effects, even when mean temperatures were below the critical maximum. Predictions based on daily average temperature underestimated negative effects of temperature on performance by ignoring daily maximum temperature, while predictions based on daytime maximum temperatures overestimated detrimental impacts by ignoring recovery under mild night-time temperatures. Our findings suggest that daily maximum temperature will play an important role in regulating natural population dynamics and should be considered in predictions. These findings have implications for natural population dynamics, particularly when considering the expected increase in extreme temperature events under climate change.
authors.affiliation: Climate Change Biology Research Group, State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No 2, Yuanmingyuan West Road, Haidian District, Beijing 100193, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Ma
authors.affiliation: Departments of Zoology and Genetics, Bio21 Institute, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Ary A
authors.initials: AA
authors.lastname: Hoffmann
authors.affiliation: Climate Change Biology Research Group, State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No 2, Yuanmingyuan West Road, Haidian District, Beijing 100193, China machunsen@caas.cn.
authors.forename: Chun-Sen
authors.initials: CS
authors.lastname: Ma
mesh_terms: D000818:Animals; D001042:Aphids / Q000254:growth & development / Q000502:physiology*; D002940:Circadian Rhythm; D005298:Fertility; D006358:Hot Temperature; D008136:Longevity; D009758:Nymph / Q000254:growth & development / Q000502:physiology; D011157:Population Dynamics
keywords: Average temperature; Climate change; Life history trait; Mild temperature; Model prediction; Temperature extreme