With recent climate warming trends, both the increase in thermal variance （i.e., diurnal temperature range; DTR） as well as increased mean temperature may impact many different organisms, especially poikilothermic i...With recent climate warming trends, both the increase in thermal variance （i.e., diurnal temperature range; DTR） as well as increased mean temperature may impact many different organisms, especially poikilothermic invertebrates. Predictions of insect developmental rates using degree-days （thermal unit accumulations above the developmental base threshold of the insect） are based on daily mean temperatures, regardless of DTR. However, non-linearity and variance in the means and extremes are often ignored. The role of thermal variance （e.g., daily temperature extremes and DTR） was evaluated experimentally for two swallowtail butterfly sister species using a common day/night photoperiod of 18 ： 6 h photo ： scoto-phase and corresponding daytime thermophase and nighttime cryophase periods of 22 ： 22℃ （constant 22℃）, 24 ： 16℃, and 26 ： 10℃（all three treatments had the same daily mean and the same degree-day accumulations）. Although developmental rates ofpost-diapause pupae were largely unaffected for both species, our results show that sizes in P canadensis females （but not males） were smaller in the treatments with more variance （26℃ ： 10℃） compared to constant 22℃. Such potentially significant impacts of size reduction in P canadensis females were not observed in P glaucus males or females under the same series ofthermo-period treatments.展开更多
基金Acknowledgments This research was supported in part by the Michigan State Agriculture Experiment Station （Project MAES 01644）and the National Science Foundation （DEB 0716683 DEB 0918879 and the REU providing support for B S and CR, DEB-0821958）. Thanks are extended to Casey Rowley for help in the early stages of this work, to Matthew Aardema for help in the lab, and to James Maudsley and Howard Romack for field assistance.
文摘With recent climate warming trends, both the increase in thermal variance （i.e., diurnal temperature range; DTR） as well as increased mean temperature may impact many different organisms, especially poikilothermic invertebrates. Predictions of insect developmental rates using degree-days （thermal unit accumulations above the developmental base threshold of the insect） are based on daily mean temperatures, regardless of DTR. However, non-linearity and variance in the means and extremes are often ignored. The role of thermal variance （e.g., daily temperature extremes and DTR） was evaluated experimentally for two swallowtail butterfly sister species using a common day/night photoperiod of 18 ： 6 h photo ： scoto-phase and corresponding daytime thermophase and nighttime cryophase periods of 22 ： 22℃ （constant 22℃）, 24 ： 16℃, and 26 ： 10℃（all three treatments had the same daily mean and the same degree-day accumulations）. Although developmental rates ofpost-diapause pupae were largely unaffected for both species, our results show that sizes in P canadensis females （but not males） were smaller in the treatments with more variance （26℃ ： 10℃） compared to constant 22℃. Such potentially significant impacts of size reduction in P canadensis females were not observed in P glaucus males or females under the same series ofthermo-period treatments.
