How doesReynoutriainvasion fit the various theories of invasibility?

Abstract

Abstract:Questions:1. How does species richness of recipient communities affectReynoutriainvasion? 2. How doesReynoutriainvasion change host community structure? 3. Are there any differences in habitat preferences among three closely relatedReynoutriataxa? 4. How does the genetic structure ofReynoutriapopulations change along the course of a river?Location:River Jizera basin, north Bohemia, Czech Republic.Methods:Nine 0.25 km2plots were chosen along the river. Within each plot all main habitat types were determined and sampled using the Braun‐Blanquet scale to determine the invasibility of various communities. The patches invaded byReynoutriataxa and surroundingReynoutria‐freevegetation in the same habitat type were sampled as relevé pairs to compare the composition of invaded and non‐invaded vegetation. In addition, to characterize the genetic structure ofReynoutriapopulations along the river, 30 samples from different clones were collected.Results and conclusions:1. The species richness of communities has no influence on the success ofReynoutriainvasion in the area studied. The combination of environmental conditions and propagule spread is more important to the invasion success than the number of species in the host community. 2.Reynoutriainvasion greatly reduces species diversity. 3.R. japonicainvaded more habitat types thanR. sachalinensisandR.×bohemica. The hybridR.×bohemicaoutcompetes the parental taxa at sites where both taxa co‐occur. 4. Isozyme analysis revealed phenotype variability in the hybrid in contrast to the parental taxa. Different hybrid phenotypes are distributed randomly on the middle and lower reaches of the River Jizera; one of them dominates and the other three occur occasionally. This pattern supports the hypothesis that sexual reproduction occasionally occurs withinReynoutriataxa.