Williams Ray S, Lincoln David E, Norby Richard J
Department of Biology, Appalachian State University, 572 Rivers Street, P.O. Box 32027, Boone, NC 28608-2027, USA.
Oecologia. 2003 Sep;137(1):114-22. doi: 10.1007/s00442-003-1327-z. Epub 2003 Jul 3.
Predicted increases in atmospheric CO(2) and global mean temperature may alter important plant-insect associations due to the direct effects of temperature on insect development and the indirect effects of elevated temperature and CO(2) enrichment on phytochemicals important for insect success. We investigated the effects of CO(2) and temperature on the interaction between gypsy moth (Lymantria dispar L.) larvae and red maple (Acer rubrum L.) saplings by bagging first instar larvae within open-top chambers at four CO(2)/temperature treatments: (1) ambient temperature, ambient CO(2), (2) ambient temperature, elevated CO(2) (+300 microl l(-1) CO(2)), (3) elevated temperature (+3.5 degrees C), ambient CO(2), and (4) elevated temperature, elevated CO(2). Larvae were reared to pupation and leaf samples taken biweekly to determine levels of total N, water, non-structural carbohydrates, and an estimate of defensive phenolic compounds in three age classes of foliage: (1) immature, (2) mid-mature and (3) mature. Elevated growth temperature marginally reduced (P <0.1) leaf N and significantly reduced ( P <0.05) leaf water across CO(2) treatments in mature leaves, whereas leaves grown at elevated CO(2) concentration had a significant decrease in leaf N and a significant increase in the ratio of starch:N and total non-structural carbohydrates:N. Leaf N and water decreased and starch:N and total non-structural carbohydrates:N ratios increased as leaves aged. Phenolics were unaffected by CO(2) or temperature treatment. There were no interactive effects of CO(2) and temperature on any phytochemical measure. Gypsy moth larvae reached pupation earlier at the elevated temperature (female =8 days, P <0.07; male =7.5 days, P <0.03), whereas mortality and pupal fresh weight of insects were unrelated to either CO(2), temperature or their interaction. Our data show that CO(2) or temperature-induced alterations in leaf constituents had no effect on insect performance; instead, the long-term exposure to a 3.5 degrees C increase in temperature shortened insect development but had no effect on pupal weight. It appears that in some tree-herbivorous insect systems the direct effects of an increased global mean temperature may have greater consequences for altering plant-insect interactions than the indirect effects of an increased temperature or CO(2) concentration on leaf constituents.
预计大气中二氧化碳（CO₂）浓度升高和全球平均气温上升可能会改变重要的植物与昆虫间的关系，这是由于温度对昆虫发育有直接影响，以及温度升高和CO₂浓度增加对昆虫生存所必需的植物化学物质有间接影响。我们通过在开顶式气室中对一龄舞毒蛾（Lymantria dispar L.）幼虫进行套袋处理，研究了CO₂和温度对舞毒蛾幼虫与红枫（Acer rubrum L.）树苗之间相互作用的影响，设置了四种CO₂/温度处理：（1）环境温度、环境CO₂浓度；（2）环境温度、升高的CO₂浓度（+300 μl l⁻¹ CO₂）；（3）升高的温度（+3.5℃）、环境CO₂浓度；（4）升高的温度、升高的CO₂浓度。将幼虫饲养至化蛹，并每两周采集一次叶片样本，以测定三种叶龄叶片中总氮、水分、非结构性碳水化合物的含量以及防御性酚类化合物的估计含量，这三种叶龄分别为：（1）未成熟叶；（2）中成熟叶；（3）成熟叶。在成熟叶片中，升高生长温度使叶片氮含量略有降低（P <0.1），并显著降低（P <0.05）叶片水分含量，而在升高的CO₂浓度下生长的叶片，其氮含量显著降低，淀粉与氮的比值以及总非结构性碳水化合物与氮的比值显著增加。随着叶片变老，叶片氮和水分含量降低，淀粉与氮的比值以及总非结构性碳水化合物与氮的比值增加。酚类物质不受CO₂或温度处理的影响。CO₂和温度对任何植物化学指标均无交互作用。在升高的温度下，舞毒蛾幼虫化蛹更早（雌性 = 8天，P <0.07；雄性 = 7.5天，P <0.03），而昆虫的死亡率和蛹鲜重与CO₂、温度或它们的交互作用均无关。我们的数据表明，CO₂或温度诱导的叶片成分变化对昆虫表现没有影响；相反，长期暴露在温度升高3.5℃的环境中会缩短昆虫发育时间，但对蛹重没有影响。看来，在一些树木 - 食草昆虫系统中，全球平均温度升高的直接影响可能比温度升高或CO₂浓度增加对叶片成分的间接影响对改变植物 - 昆虫相互作用具有更大的影响。
