Population biology of the Japanese knotweeds: Alien invasive species of the genus Fallopia Adans. (Polygonaceae) in Belgium


The Japanese knotweeds are invasive alien clonal species originating in Asia (Japan, Korea, Taiwan and Nord of China). They were introduced in Europe at the beginning of the 19è century. They are now some of the most troublesome invasive alien species in Europe and in the United States. In Belgium, a complex of four taxa and a hybrid represents them. All these taxa take part in the pattern of invasion and represent an excellent opportunity for studies of population biology in Western continental Europe. The presence from at least three taxa and a hybrid is confirmed by cytological, genetic and morphological studies. Vegetative reproduction is recognized as the main mode of reproduction and expansion of these taxa in the introduce range. However, interspecific hybridization events are observed confirming the restoration of the sexual reproduction by hybridization within this complex species in Belgium. Hybrid F. x bohemica with various ploidy levels from tetraploid to octoploid is observed. An increase in genotypic and morphological diversity is shown at the hybrid F. x bohemica which missed with the parental species. This could increase the potential of Japanese knotweeds to adapt to the new environment and contribute to the invasive success of these taxa in Belgium. Assignment test indicates a genetic pool differentiated at the hybrid F. x bohemica and not a mixture of the genetic pool of the parental species as expected for hybrid taxa. Hybrid F. x bohemica has always been considered as rare in Belgium and of horticultural origin. An analysis of the spatial distribution shows that hybrid F. x bohemica is widespread in Belgium and that its abundance depends on the areas. An analysis of extent of differentiation between groups of hybrid geographically distant could not provide proof of an independent evolution of hybrid populations under limited gene flow. An analysis of the sexual reproduction capacity and dispersal of seeds shows important production of viable seeds and consequent seed rain. Hybrid seeds may be dispersed beyond 16m, leading the possibility of founding new individuals and to contribute to the invasive success of these taxa. However, a trend towards decreasing germination rate is shown after a cold period. An analysis of the distribution at the landscape scale shows that the dynamics of colonization of habitats patches by Japanese knotweeds rising mainly from clonal propagation in spite of important pressure of propagule. The knotweeds prefer human disturbed habitats with a clear prevalence of communication routes. This leads the possibility of dispersing towards the adjacent habitats patches. A high dynamics of establishment of propagule was not observed at the hybrid plants compared with the parents plants in spite of the increase in genotypic diversity and the consequent pressure of propagule. Lastly, proposals for the integrated management of these taxa are proposed in the Belgium context. Their management will have first to identify hybrids and taxa involved. Emasculation and management of the existing clones represent solutions to prevent flowering and expansion of these taxa. An active management of disturbed habitats may represent alternative to prevent the invasion by Japanese knotweeds.


Biological invasions, Evolution, Interspecific hybridization, Belgium, Japanese knotweeds, Polygonaceae, Morphology, Genotypic diversity, Sexual reproduction, Differential selection, Polyploidie, Landscape ecology, Spatial distribution, SIG, Habitat selection, Population biology, Fallopia aubertii, Fallopia japonica, Fallopia sachalinensis, Fallopia x bohemica, RAPDs, Flow cytometry, Chromosome counts, Floral biology, Pollination succes, Reproductive success, Fruit set, Seed rain, Seed bank, Seed viability, Seed germination, Cytology, Seed dispersal, Dispersal capacity, Sexual reproduction, Landscape scale distribution, Dynamics of colonization, Habitats patches, Rate of colonization, Rate of spread, Clonal propagation, Spatial scale, Invasion control, Habitat protection, Management priorities


Population and Ecological Genetics {Research discipline}
Plant Systematics, Taxonomy and Phylogeny {Research discipline}
Terrestrial Ecology {Research discipline}
Landscape Ecology {Research discipline}
Life Histories (incl. Population Ecology) {Research discipline}
Conservation and Biodiversity {Research discipline}
Biogeography {Research discipline}
Ecology and Evolution not elsewhere classified {Research discipline}
Global Change Biology {Research discipline}
Genetic {Integration level}
Species {Integration level}
Ecosystem {Integration level}
European (EU) {Cooperation status}
Monitoring of Biodiversity {Research orientation}
Conservation, Restoration and Sustainable use of Biodiversity {Research orientation}
Europe {Geographical scope}
Belgium {Geographical scope}
Agricultural {Habitat type}
Forest {Habitat type}
General Measures for Conservation and Sustainable Use {Research purpose}
Access to and Transfer of Technology {Research purpose}
Exchange of Information {Research purpose}
Technical and Scientific Cooperation {Research purpose}
Identification and Monitoring {Research purpose}
Incentive Measures {Research purpose}
Research and Training {Research purpose}
Public Education and Awareness {Research purpose}
Impact Assessment and Minimizing Adverse Impacts {Research purpose}
Plantae {Taxonomical scope}


Name Role Start End
Mahy, Grégory promotor 2001-10-01 2007-10-01
Tiébré, Marie-Solange member 2001-10-01 2007-10-01


Name Role Start End
Biodiversity and Landscape Unit member 2001-10-01


Reference Role
Tiébré M.-S., Vanderhoeven S., Saad L., and Mahy G. 2007. Hybridization and sexual reproduction in the invasive alien Fallopia (Polygonaceae) Complex in Belgium. Annals of Botany 99:193-203. author
Meerts P., et Tiébré M.-S. 2007. Fallopia x bohemica est beaucoup plus répandu que F. sachalinensis dans la région de Bruxelles. Dumortiera 92: 22-24 author
Saad L., Tiébré M.-S., Hardy O., Mahy G., Vanderhoeven S. Comparative study of hybridisation patterns in adults and seedlings of the invasive alien Fallopia (Polygonaceae) complex. Soumis. Preslia author
Tiébré M.-S., J.-P. Bizoux, O. J. Hardy, J. P. Bailey, et Mahy G. 2007. Hybridization and morphogenetic variation in the invasive alien Fallopia (Polygonaceae) complex in Belgium. American Journal of Botany 94: 1900-1910 author
Tiébré, M.-S., Saad, L., Mahy G. Landscape scale distribution and habitat selection by invasive alien species Fallopia (Polygonaceae) complex in Belgium. Accepté avec modifications mineures. Biodiversity and Conservation author

created:2011-12-14 14:18:59 UTC, source:web

© 2012 by the Belgian Biodiversity Platform