Pascal Karitter , Emma Corvers, Marie Karrenbauer, Martí March-Salas, Bojana Stojanova, Andreas Ensslin, Robert Rauschkolb, Sandrine Godefroid, J F Scheepens

1. 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 by imposing significant selection pressures and forcing plants to optimize resource use against competitors. Although recent studies have demonstrated the rapid and ongoing evolution of European plants to global change dynamics, the evolution of competitive ability in the context of changes in nutrient availability remains understudied.
2. In this study, we investigated whether the common calcareous grassland herb Leontodon hispidus recently evolved its competitive ability and response to nutrient availability. We grew ancestors sampled in 1995 and descendants sampled in 2018 from a single population under common conditions and applied a competition treatment using the natural competitor Brachypodium pinnatum. Furthermore, we applied nutrient treatments to plants grown under competition, supplying plants weekly with either no fertilizer, or with nitrogen, phosphorus, or both.
3. 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. Furthermore, we observed evolution of taller flower stems, which may reflect a strategy to increase pollinator visits under the existing pollinator decline in recent decades.
4. Overall, our study demonstrates rapid contemporary evolution, 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.