In the Mediterranean and temperate regions, an increase in the frequency and intensity of drought events has been recorded, probably due to climate change. In consequence, trees will more frequently experience hydric stress, a condition that can be expected to affect insect–tree interactions, while adaptation mechanisms may be further in course. The effect of tree water stress on the performance of two allochronic populations of Thaumetopoea pityocampa was here studied. Namely, we compared a unique population of this insect, in which the larvae develop in the summer (SP), with the typical population having winter larval development (WP), to test the adaptation hypothesis to host plant status. Larvae of each population were fed on needles of young potted Pinus pinaster plants under two water supply regimes: (i) well-watered (control) and (ii) subjected to 3 months of drought stress. Compared to control, stressed plants had higher amounts of soluble sugars, phenols, and higher C/N ratio, whereas water content and chlorophylls concentrations were lower. In general, T. pityocampa larvae had lower performances on water-stressed plants, as shown by lower survival rates, lower needle consumption, and longer development times. Yet, the detrimental effects of tree stress were only significant for the WP larvae, while SP larvae were able to overcome such conditions. Results demonstrate that tree water stress can negatively affect T. pityocampa populations. Furthermore, the evidence is also provided that responses to the physiological condition of the host trees may occur at the population level, as a result of adaptation mechanisms driven by climate change.

中文翻译：

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松行蛾的物候变化影响树虫相互作用的结果

在地中海和温带地区，已经记录到干旱事件的频率和强度有所增加，这可能是由于气候变化。因此，树木将更频繁地经历缺水压力，这种情况预计会影响昆虫与树木的相互作用，而适应机制可能会进一步发展。树木水分胁迫对两种异时种群性能的影响苦瓜在这里学习。即，我们比较了这种昆虫的独特种群，其中幼虫在夏季 (SP) 发育，与具有冬季幼虫发育 (WP) 的典型种群进行比较，以检验对宿主植物状态的适应假设。每个种群的幼虫都以幼盆的针头喂养松属两种供水方式下的植物：(i) 浇水充足（对照）和 (ii) 经受 3 个月的干旱胁迫。与对照相比，胁迫植物具有较高的可溶性糖、酚和较高的C/N比，而水分含量和叶绿素浓度较低。一般来说，T.pityocampa幼虫在缺水植物上的表现较差，这表现为较低的成活率、较低的针头消耗和较长的发育时间。然而，树木压力的不利影响仅对 WP 幼虫显着，而 SP 幼虫能够克服这些条件。结果表明，树木水分胁迫会对T.pityocampa人口。此外，还提供了证据表明，由于气候变化驱动的适应机制，对寄主树木生理状况的反应可能发生在种群水平上。