Inhaltszusammenfassung

The invasion success of plants into new regions and ecosystems is assumed to depend on certain constellations of species traits. Often, effective sexual reproduction and the generation of high performance genotypes allow invaders to rapidly colonize even unfavourable sites by demonstrating high plasticity. Interspecific hybridisation, can produce such high performance genotypes, which may serve as an evolutionary stepping stone for invaders of limited genetic variability. A very aggressive i...The invasion success of plants into new regions and ecosystems is assumed to depend on certain constellations of species traits. Often, effective sexual reproduction and the generation of high performance genotypes allow invaders to rapidly colonize even unfavourable sites by demonstrating high plasticity. Interspecific hybridisation, can produce such high performance genotypes, which may serve as an evolutionary stepping stone for invaders of limited genetic variability. A very aggressive invader with particularly limited genetic variability is the Japanese Knotweed (Fallopia japonica). Hybridisation with the Giant Knotweed Fallopia sachalinensis in recent years, however, has created the hybrid Bohemian Knotweed (Fallopia × bohemica) presenting new opportunities for the species complex. An accelerated invasion process could be the result. We assessed whether or not different taxa of the F. japonica species complex would exhibit different growth potential depending on site conditions. After taxon identification for over 100 samples using genetic markers (microsatellite DNA), we combined the data with observations on Fallopia stand growth, horizontal spreading behaviour, flowering and seed set in relation to different environmental site conditions across an ecologically diverse region in Germany (Rhineland Palatinate). The majority of the samples were interspecific hybrids, which is an outstanding finding compared to earlier studies. The hybrids were genetically diverse exhibiting a high number of multilocus genotypes, suggesting that sexual reproduction is a major strategy for generating new genotypes and for dispersal. Hybrids that were closely related to F. japonica exhibited the highest potential for aggressive growth in terms of horizontal spreading and reduction of competitor plants within stands. Site conditions, especially N-supply, contributed to the aggressive growth found but were less relevant than taxonomic characteristics. Moreover, several hybrids set a lot of seeds that germinated very well. We demonstrated that hybridisation is able to generate new high performance genotypes and enables the taxa to accelerate and increase the invasion potential. Our study provides new insights into the invasiveness of alien plants in general and for the taxa F. japonica s. l. in particular.» weiterlesen» einklappen

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