Nitrogen fertilization and high plant growing temperature increase herbivore performance

Global environmental change exerts growing pressure on biodiversity.
Anthropogenic climate and land use change are particularly important
drivers of biodiversity loss. While their effects on biodiversity have
been widely studied individually, interactions among them are poorly
understood. Here, we investigate the effects of two common drivers of
global change, increased temperature and nitrogen fertilization, on
host-plant quality and herbivore performance in the butterfly Lycaena
tityrus. We show that butterfly performance was positively affected by
plants grown at increased temperatures and nitrogen fertilization, the
latter being in line with the nitrogen limitation hypothesis. Effects were
largely consistent across treatments, i.e. nitrogen deposition and
temperature did not interact strongly to affect herbivore performance.
Overall, females suffered more strongly than males from poor host-plant
quality. Our study demonstrates changes in host-plant quality caused by
variation in temperature and nitrogen availability, which induced indirect
effects in an herbivore. Such indirect effects of global environmental
change are an important source of variation and should be considered in
order to reduce uncertainties with regard to the effects of global change
on biodiversity.

全球环境变化正对生物多样性施加日益严峻的压力。人为引发的气候变化与土地利用变化，是驱动生物多样性丧失的关键因子。尽管二者对生物多样性的单一效应已被广泛研究，但二者间的交互作用却鲜有深入解析。本研究以红灰蝶（Lycaena tityrus）为研究对象，探讨全球变化的两类常见驱动因子——升温与氮肥施用——对寄主植物品质及植食性昆虫生长表现的影响。研究结果表明，经升温与氮肥处理培育的寄主植物，可显著正向提升蝶类的生长表现，其中氮肥处理的效应符合氮限制假说（nitrogen limitation hypothesis）。各处理组的效应整体较为一致，即氮沉降与升温并未对植食性昆虫的生长表现产生显著的交互作用。总体而言，相较于雄性个体，雌性个体受寄主植物品质低下的负面影响更为显著。本研究证实，温度与氮素可获得性的变化会改变寄主植物品质，进而对植食性昆虫产生间接效应。全球环境变化所引发的这类间接效应，是导致生物多样性效应研究结果存在变异的重要来源，因此在评估全球变化对生物多样性的影响时，需将此类间接效应纳入考量，以降低相关研究的不确定性。