Competition is commonly thought to underlie the impact of plant invasions. However, competitive effects of aliens and competitive response of natives may also change over time. Indeed, as with time the novelty of an invader decreases, the accumulated eco-evolutionary experience of resident species may eventually limit invasion success. We aimed to gain insights on whether directional changes in biotic interactions over time, or more general differences between natives and aliens, for instance resulting from an introduction bias, are relevant in determining competitive ability. We conducted a pairwise competition experiment in a target-neighbour design, using 47 Asteraceae species with residence times between 8-12,000 years in Germany. We first tested whether there are differences in performance in intraspecific competition among invasion status groups, that is casual and established neophytes, archaeophytes, or native species. We then evaluated whether competitive response and effects depend on residence time or invasion status. Lastly, we assessed whether competitive effects influence range sizes. We found only limited evidence that native target species tolerate neighbours with longer potential coexistence times better, whereas differences in competitive ability were mostly better explained by invasion status than residence time. Although casual neophytes produced most biomass in intraspecific competition, they had the weakest per-capita competitive effects on natives. Notably, we did not find differences between established neophytes and natives, both of which ranked highest in interspecific competitive ability. This lack of differences might be explained by a biased selection of highly invasive or rare native species in previous studies, or because invasion success may result from mechanisms other than interspecific competitive superiority. Accordingly, interspecific per-capita competitive effects did not influence range sizes. Further studies across a broader range of environmental conditions, involving other biotic interactions that indirectly influence plant-plant interactions, may clarify when eco-evolutionary adaptations to new invaders are a relevant mechanism.

The dataset contains two files. The file "SheppardBrendelNeoBiota_Experimentaldata.csv" contains data collected on Asteraceae plants in each pot of a competition experiment conducted at the Heidfeldhof experimental station of the Faculty of Agricultural Sciences, University of Hohenheim, Stuttgart, in summer 2017. The file "SheppardBrendelNeoBiota_CompeffectsRangesize.csv" contains data from the results of species-specific regressions to determine competitive effects and data on range sizes of competitor species.

Detailed description of the variables in this dataset is available in the uploaded Metadata file. Further explanations and descriptions of the analysis of the data is explained in the Methods section and Supplementary File of the research article.