The Ecological Impact of Lupinus polyphyllus Spread in Sweden

Invasive species represent a growing threat to biodiversity in temperate grasslands, yet their effects are often contingent on environmental context and species traits. This study examines the spatial, temporal, and ecological impacts of Lupinus polyphyllus in Sweden, using species occurrence data from the Global Diversity Information Facility (GBIF), environmental covariates, and functional guild classifications. From 2004-2024, lupine records increased fourfold, with the highest densities observed in municipalities combining elevated soil nitrogen,  warm temperatures, and high precipitation. A negative-binomial mixed model did not detect a statistically significant three-way interaction among nitrogen, temperature, and precipitation (p=0.161), but plotted trends suggest climate-dependent variation in nitrogen effects. To assess community impact, a novel damage index was calculated for 24 native plant taxa. Species responses varied widely, with competitive generalists such as Festuca ruba increasing by over 300%, while nutrient-stress specialists like Orchis mascula declined by more than 50% in high-lupine municipalities. Pearson correlations supported these patterns, and guild-level trends broadly aligned with nutrient tolerance and disturbance sensitivity. Although trait-based regression models were inconclusive, community responses were structured by ecological strategies, which stresses the importance of functional-trait perspectives. In northern municipalities, standardized lupine presence remains high despite recent declines in raw occurrence records, consistent with invasion debt. These findings highlight the need for climate-informed control efforts, early detection in high-suitability areas, and habitat-specific management prioritizing vulnerable species. By integrating species-level patterns with trait-based guild responses, this study shows how L. polyphyllus acts as an environmental filter, reshaping native plant communities in ways that depend on both biophysical context and species ecology.