Data for: Simulating effects of agricultural intensification and climate change: Nitrogen fertilization and drought stress decrease insect herbivore performance

Biodiversity is globally under pressure, and the current decline in insect biomass and diversity is likely caused by human activities. Key drivers of biodiversity loss include agricultural intensification and anthropogenic climate change. Nevertheless, a thorough understanding of potential interactions between both factors and the mechanisms underlying insect declines in general is still lacking.

Here, we investigate the combined effects of nitrogen fertilization and drought, as applied to host plants, on the preference and performance of the butterfly Lycaena tityrus.

Individuals performed best on plants having received medium nitrogen levels, while performance was reduced by either a lack of or strong fertilization, the former potentially caused by nitrogen limitation and the latter by increased concentrations of toxic allelochemicals. Female oviposition preference though was positively related to nitrogen fertilization, resulting in a mismatch between preference and offspring performance at high nitrogen levels. Plant drought stress additionally reduced herbivore performance, and females appeared to suffer more from low-quality food than males.

Our results indicate that increasing nitrogen fertilization, as applied in intensive agriculture, may substantially reduce host-plant quality for insect herbivores, which may be exaggerated in the course of climate change due to the more frequent occurrence of droughts. Our study thus contributes to a better understanding of the mechanisms underlying human-driven insect declines in agricultural landscapes and beyond.

全球生物多样性正面临严峻压力，当前昆虫生物量与多样性的衰退大概率由人类活动所引发。生物多样性丧失的关键驱动因素包括农业集约化与人为气候变化。然而，学界目前仍缺乏对这两类因素间潜在相互作用，以及昆虫种群整体衰退背后深层机制的全面认知。

本研究针对宿主植物施加氮肥与干旱处理，探究其对灰蝶（Lycaena tityrus）的寄主选择偏好与子代适合度表现的联合影响。

试虫在施予中等氮肥水平的宿主植物上表现出最优的适合度；氮肥不足或过量均会降低其适合度：前者可能源于氮素限制，后者则由有毒化感物质（allelochemicals）浓度升高所导致。尽管雌性成虫的产卵偏好与氮肥施用量呈正相关，但这一偏好与高氮水平下子代的适合度表现出现错配。此外，植物干旱胁迫会进一步削弱植食性昆虫的适合度，且雌性个体相较于雄性更易受到低质量食物的负面影响。

本研究结果表明，集约化农业中普遍采用的氮肥增施措施，可能会大幅降低植食性昆虫的宿主植物质量；而在气候变化进程中，干旱事件发生频率愈发频繁，这一负面影响或进一步加剧。综上，本研究有助于深化对农业景观乃至更广范围内人类活动驱动昆虫种群衰退背后机制的理解。