In Poland, Anthriscus caucalis reaches the north-eastern limit of its secondary geographical range in Central Europe and is declining archaeophyte in ruderal habitats. However, in recent years, new localities of A. caucalis were found in the north-western and western Poland in forest communities. A high number of individuals of A. caucalis in these localities suggests that it finds optimal growth conditions in these strongly eutrophic forests, exhibiting an invasive potential in this habitat. To compare the floristic composition and habitat conditions between ruderal and forest plant communities occupied by A. caucalis in Poland, a total of 23 relevés were collected. For each vegetation plot, median Ellenberg’s indicator values (EIV) were estimated in order to evaluate the environmental conditions. The differences in EIV and floristic composition between the localities were analysed using the Non-Metric Multi-Dimensional Scaling (NMDS). In addition, we examined the ITS1-5.8S-ITS2 sequence variation for five individuals from four populations to analyse the association of particular genotype with ruderal or forest habitat. The results showed that the specific configuration of environmental factors, including moderate shade, mild and stable thermal and moisture conditions as well as high concentration of nutrients in the soil, is more important to A. caucalis occurrence than the floristic composition of the plant communities. Therefore, we hypothesize that the vanishing of A. caucalis in the ruderal habitats is a response to the currently observed increase of the extreme weather events. Likely, it finds more suitable and stable microclimate conditions in the forest areas. The results of the molecular analyses revealed two ribotypes which occurred in both types of habitats. The lack of correlation between genotype and habitat supports our conclusion from EIV analysis that the colonization of forests should be treated rather as a niche tracking than as an adaptive shift in habitat preference.

Keywords: alien species, Central Europe, Ellenberg’s indicator values (EIV), ITS rDNA