Plant distribution patterns in Germany – Will aliens match natives?

Using data on the distribution of the German vascular flora and a wide selection of environmental data we address questions regarding native and alien plant distribution patterns. We found highly significant positive relationships between plant species richness of natives and aliens on three spatial scales (c. 100 km 2 , c. 1,000 km 2 , c. 10,000 km 2 ). Given the results of major axis regressions on log‐transformed data, we conclude that alien species richness increases overproportionately compared to native species richness. To determine common factors for plant richness patterns, we used a principal component analysis (PCA) to reduce the number of environmental variables. The principal components were used in a multiple regression as independent variables to model plant species richness of aliens and natives, corrected for spatial autocorrelation. The diversity of geological substrates is considered most important for native and alien plant species richness. Furthermore, area of loess subsoils is important for archaeophyte richness, urbanisation is important for neophyte richness. Comparisons of similarity matrices between natives and aliens using standardised similarities as well as Simpsons similarities of randomly selected grid cells showed a positive correlation. Similarity patterns provided by native plant species are traced by archaeophytes but not followed by neophytes. Similarities of archaeophytes were significantly higher than those of natives whereas similarities of neophytes where significantly lower than those of natives. Therefore, we concluded that archaeophytes lead to homogenisation of the German flora but are mainly plants of arable fields that are homogeneous due to human land use. Neophytes, however, did not lead to homogenisation but increase local biodiversity.