Department of Terrestrial Ecology, Netherlands Institute of Ecology, Droevendaalsesteeg 10, Wageningen, 6708 PB, The Netherlands.
Department of Ecological Science, Section Animal Ecology, VU University Amsterdam, De Boelelaan 1085, Amsterdam, 1081 HV, The Netherlands.
Ecology. 2019 Nov;100(11):e02819. doi: 10.1002/ecy.2819. Epub 2019 Aug 20.
Changes in the frequency, duration, and intensity of rainfall events are among the abiotic effects predicted under anthropogenic global warming. Heavy downpours may profoundly affect the development and survival of small organisms such as insects. Here, we examined direct (physically on the insects) and indirect (plant-mediated) effects of simulated downpours on the performance of caterpillars of two lepidopteran herbivores (Plutella xylostella and Pieris brassicae) feeding on black mustard (Brassica nigra) plants. Host plants were exposed to different rainfall regimes both before and while caterpillars were feeding on the plants in an attempt to separate direct and indirect (plant-mediated) effects of rainfall on insect survival and development. In two independent experiments, downpours were simulated as a single long (20 min) or as three short (5 min) daily events. Downpours had a strong negative direct effect on the survival of P. xylostella, but not on that of P. brassicae. Direct effects of downpours consistently increased development time of both herbivore species, whereas effects on body mass depended on herbivore species and downpour frequency. Caterpillar disturbance by rain and recorded microclimatic cooling by 5°C may explain extended immature development. Indirect, plant-mediated effects of downpours on the herbivores were generally small, despite the fact that sugar concentrations were reduced and herbivore induction of secondary metabolites (glucosinolates) was enhanced in plants exposed to rain. Changes in the frequency of precipitation events due to climate change may impact the survival and development of insect herbivores differentially. Broader effects of downpours on insects and other arthropods up the food chain could seriously impair and disrupt trophic interactions, ultimately destabilizing communities.
降雨事件的频率、持续时间和强度的变化是人为全球变暖下预测的非生物效应之一。暴雨可能会对昆虫等小型生物的发育和生存产生深远的影响。在这里，我们研究了模拟降雨对两种鳞翅目食草昆虫（小菜蛾和菜粉蝶）幼虫在食用黑芥菜（Brassica nigra）植物时的直接（对昆虫本身的物理影响）和间接（通过植物介导）的影响。在毛毛虫进食的同时，尝试将降雨对昆虫存活和发育的直接和间接（通过植物介导）影响分开，宿主植物在暴露于不同的降雨模式之前和之后都受到了不同的降雨模式的影响。在两个独立的实验中，降雨被模拟为单次长（20 分钟）或三次短（5 分钟）的每日事件。降雨对小菜蛾的存活有强烈的直接负面影响，但对菜粉蝶的存活没有影响。降雨对两种食草动物的直接影响都一致地延长了其发育时间，而对体重的影响则取决于食草动物的种类和降雨频率。降雨对毛毛虫的干扰以及记录的微气候降温 5°C 可能解释了未成熟发育的延长。尽管暴露于雨中的植物中的糖浓度降低，并且食草动物诱导的次生代谢物（硫代葡萄糖苷）增强，但降雨对食草动物的间接、植物介导的影响通常较小。由于气候变化导致降水事件频率的变化可能会对昆虫食草动物的存活和发育产生不同的影响。降雨对昆虫和食物链中其他节肢动物的更广泛影响可能会严重损害和破坏营养相互作用，最终使群落不稳定。
