Evolution of competitive ability and the response to nutrient availability: A resurrection study with the calcareous grassland herb, Leontodon hispidus

Rapid environmental changes across Europe include warmer and increasingly variable temperatures, changes in soil nutrient availability, and pollinator decline. These abiotic and biotic changes can affect natural plant populations and force them to optimize resource use against competitors. To date, the evolution of competitive ability in the context of changes in nutrient availability remains understudied. In this study, we investigated whether the common calcareous grassland herb Leontodon hispidus recently evolved its competitive ability and response to nutrient availability. We compared ancestors sampled in 1995 and descendants sampled in 2018 and applied a competition treatment in combination with weekly nutrient treatments (no fertilizer, nitrogen, phosphorus, and both). We found evidence for evolution of increased competitive ability, with descendants producing more vegetative biomass than ancestors when grown under competition. The competitive ability also depended on the nutrient treatment, indicating that descendants might be adapted to lower nitrogen concentrations, which could be linked to the decreasing nitrogen emissions into the atmosphere since the 1990s. Our study demonstrates rapid contemporary evolution of competitive ability, but also the complexity of the underlying processes of contemporary evolution, and sheds light on the importance of understudied potential selection agents such as nutrient availability.

欧洲境内正经历快速的环境变化，包括气温升高且波动加剧、土壤养分有效性改变，以及传粉者衰退。这些非生物（abiotic）与生物（biotic）环境变化会影响天然植物种群，并迫使它们优化资源利用策略以对抗竞争者。迄今为止，针对养分有效性变化背景下植物竞争能力演化的研究仍较为匮乏。本研究以欧洲常见石灰质草原草本植物硬毛狮齿菊（Leontodon hispidus）为研究对象，探究其是否近期发生了竞争能力与养分有效性响应模式的演化。我们采集了1995年的种群祖先样本与2018年的种群后代样本，并设置了竞争处理结合每周养分处理的实验方案，养分处理组涵盖无肥、单施氮、单施磷以及氮磷配施四种处理方式。实验结果发现了竞争能力演化增强的证据：在竞争培养条件下，后代样本的营养生物量显著高于祖先样本。此外，竞争能力同时受养分处理的调控，这表明后代种群可能适应了低氮环境，而这或许与20世纪90年代以来大气氮排放量下降的趋势存在关联。本研究不仅证实了竞争能力可发生快速的当代演化，同时也揭示了当代演化背后过程的复杂性，并为尚未被充分研究的潜在选择因子（如土壤养分有效性）的重要性提供了新的科学认知。