Authors: Hejda, Martin; Sádlo, Jiří;Kutlvašr, Josef;Petřík, Petr;Vítková, Michaela ;Vojík, Martin;Pyšek, Petr;Pergl, Jan;

Invasive alien plants reduce the local diversity and contribute to the homogenization of plant communities on larger scales.
In this study, we selected 10 native and 9 invasive dominants and compared their impacts on the within-community scale. We identified populations with these target dominants and recorded plots with their varying cover (~dominance) within each population. The impact was then estimated using LMM regressions, relating the species richness and diversity to the dominants' cover. The impacts were compared using the slope/intercept ratios of LMM regressions, accounting for the a priory different species richness and diversity of recipient communities.
Native dominants, such as Calamagrostis epigejos, Phalaris arundinacea or Urtica dioica reduce the diversity in a magnitude similar to invasive dominants, such as Fallopia sp. div.
Furthermore, we compared the impacts of native versus alien dominants, selected as to occupy the same habitats. Native Calamagrostis epigejos, Phalaris arundinacea and Cirsium oleraceum had stronger impacts than alien Aster novi-belgii, Impatiens glandulifera and Lupinus polyphyllus, respectively. However, Aster novi-belgii and Rumex alpinus had larger impacts than native Tanacetum vulgare and Cirsium heterophyllum.
Our results support the idea that management efforts should aim to suppress dominant species in general, regardless of their origin.