[en] The invasive alien knotweeds, Fallopia spp. (Polygonaceae), are some of the most troublesome invasive species in Europe and North America. Invasive success in Fallopia may be enhanced by multiple hybridization events. We examined the pattern of hybridization and its evolutionary consequences in Belgium with a concerted analysis of ploidy levels (chromosome counts and
flow cytometry), morphological variation, and genetic variation (RAPDs). At least four taxa with different ploidy levels were part of the pattern of invasion in Belgium. Hybrid F.3bohemica with various chromosome numbers restored the genotypic diversity that was lacking in the parental species. Hybrid genotypes were mainly assigned to a specific genetic pool and not to a mixture
between the genetic pools of the putative parental species as would be expected for hybrids. Parental species and hexaploid hybrids differed significantly for a set of well-defined morphological characters, enabling future researchers to distinguish these taxa. On the basis of our results, the importance of hybridization has probably been underestimated in large parts of the adventive range of alien Fallopia species, pointing to the need for concerted molecular and morphological analyses in the study of the evolutionary consequences of hybridization.
ABBOTT, R. J. 1992. Plant invasions, interspecific hybridization and the evolution of new plant taxa. Trends in Ecology and Evolution 7: 401-405.
ABBOTT, R. J. 2000. Hybrid origin of the Oxford ragwort, Senecio squalidus L. Watsonia 23: 123-138.
AINOUCHE, M. L., A. BAUMEL, A. SALMON, AND G. YANNIC. 2003. Hybridization, polyploidy and speciation in Spartina (Poaceae). New Phytologist 161: 165-172.
ALLENDORF, F. W., AND L. L. LUNDQUIST. 2003. Introduction: population biology, evolution and control of invasive species. Conservation Biology 17: 24-30.
BAILEY, J. P. 1988. Putative Reynoutria japonica Houtt. X Fallopia baldschuanica (Regel) Holub hybrids discovered in Britain. Watsonia 17: 163-164.
BAILEY, J. P. 1989. Cytology and breeding behaviour of giant alien Polygonum species in Britain. Ph.D. dissertation, University of Leicester, Leicester, UK.
BAILEY, J. P. 1994. Reproductive biology and fertility of Fallopia japonica (Japanese knotweed) and its hybrids in the British Isles. In L. C. De Waal, L. E. Child, P. M. Wade, and J. H. Brock [eds.], Ecology and management of invasive riverside plants, 141-158. Wiley and Sons, Chichester, UK.
BAILEY, J. P. 2001. Fallopia Xconollyana the railway-yard knotweed. Watsonia 23: 539-541.
BAILEY, J. P. 2003. Japanese knotweed s. l. at home and abroad. In L. Child, J. H. Brock, G. Brundu, K. Prach, P. Pyšek, M. Wade, and M. Williamson [eds.], Plant invasions: ecological threats and management solutions, 183-196. Backhuys Publishers, Leiden, Netherlands.
BAILEY, J. P., L. CHILD, AND A. P. CONOLLY. 1996. A survey of the distribution of Fallopia X Bohemica (Chrtek & Chrtkova) J. Bailey (Polygonaceae) in the British Isles. Watsonia 21: 187-198.
BAILEY, J. P., AND C. A. STACE. 1992. Chromosome number, morphology, pairing, and DNA values of species and hybrids in the genus Fallopia (Polygonaceae). Plant Systematics and Evolution 180: 29-52.
BAILEY, J. P., AND R. WISSKIRCHEN. 2006. The distribution and origins of Fallopia Xbohemica (Polygonaceae) in Europe. Nordic Journal of Botany 24: 173-199.
BARRAL, V. 1994. Biologie et biogéographie de Polygonum cuspidatum. Mémoire de Maîtrise, Université Joseph Fourier, Grenoble, France.
BEERLING, D. J., J. P. BAILEY, AND A. P. CONOLLY. 1994. Biological flora of the British Isles: Fallopia japonica (Houtt.) Ronse De Craene. Journal of Ecology 82: 959-979.
BÍMOVÁ, K. B. E., B. B. C. MANDÁK, AND P. PYŠEK. 2003. Experimental study of vegetative regeneration in four invasive Reynoutria taxa (Polygonaceae). Plant Ecology 166: 1-11.
CALLAWAY, R., AND J. MARON. 2006. What have exotic plant invasions taught us over the past 20 years? Trends in Ecology and Evolution 21: 369-374.
CATTELL, M. V., AND S. A. KARL. 2004. Genetics and morphology in a Borrichia frutescens and B. arborescens (Asteraceae) hybrid zone. American Journal of Botany 91: 1757-1766.
CHILD, L., AND M. WADE. 2000. The Japanese knotweed manual. Packard Publishing, Chichester, West Sussex, UK.
DIDHAM, R. K., J. M. TYLIANAKIS, M. A. HUTCHISON, R. M. EWERS, AND N. J. GEMMELL. 2005. Are invasive species the drivers of ecological change? Trends in Ecology and Evolution 20: 470-474.
DOYLE, J. J., AND J. L. DOYLE. 1990. Isolation of plant DNA from fresh tissue. Focus 12: 13-15.
ELLSTRAND, N. C., AND K. A. SCHIERENBECK. 2000. Hybridization as a stimulus for the evolution of invasiveness in plants? In variation and evolution in plants and microorganisms: toward a new synthesis 50 years after Stebbins. Proceedings of the National Academy of Sciences, USA 97: 7043-7050.
EUNMI, L. C. 2002. Evolutionary genetics of invasive species. Trends in Ecology and Evolution 17: 386-391.
EVANNO, G., S. REGNAUT, AND J. GOUDET. 2005. Detecting the number of clusters of individuals using the software Structure: a simulation study. Molecular Ecology 14: 2611-2620.
FJELLHEIM, S., R. ELVEN, AND C. BROCHMANN. 2001. Molecules and morphology in concert. II. The Festuca brachyphylla complex (Poaceae) in Svalbard. American Journal of Botany 88: 869-882.
FOJCIK, B., AND B. TOKARSKA-GUZIK. 2000. Reynoutria Xbohemica (Polygonaceae): nowy takson we florze Polski. Fragmenta Floristica et Geobotanica Polonica 7: 63-71.
GODEFROID, S. 1996. A propos de l'extension spectaculaire de Fallopia japonica, F. sachalinensis, Buddleja davidii et Senecio inaequidens en région bruxelloise. Dumotiera 63: 9-16.
GROSHOLZ, E. 2002. Ecological and evolutionary consequences of costal invasions. Trends in Ecology and Evolution 17: 22-27.
GUREVITCH, J., AND D. PADILLA. 2004. Are invasive species a major cause of extinctions? Trends in Ecology and Evolution 19: 470-474.
HÄNFLING, B., AND J. KOLLMANN. 2002. An evolutionary perspective of biological invasions. Trends in Ecology and Evolution 17: 545-546.
HANSEN, K. T., R. ELVEN, AND C. BROCHMANN. 2000. Molecules and morphology in concert: tests of some hypotheses in arctic Potentilla (Rosaceae). American Journal of Botany 87: 1466-1479.
HEGARTY, M. J., AND S. J. HISCOCK. 2005. Hybrid speciation in plants: new insights from molecular studies. New Phytologist 165: 411-423.
HOLLINGSWORTH, M. L., AND J. P. BAILEY. 2000. Hybridisation and clonal diversity in some introduced Fallopia species (Polygonaceae). Watsonia 23: 111-121.
HOLLINGSWORTH, M. L., J. P. BAILEY, P. M. HOLLINGSWORTH, AND C. FERRIS. 1999. Chloroplast DNA variation and hybridization between invasive populations of Japanese knotweed and giant knotweed (Fallopia, Polygonaceae). Botanical Journal of the Linnean Society 129: 139-154.
HOLLINGSWORTH, M. L., P. M. HOLLINGSWORTH, G. I. JENKINS, J. P. BAILEY, AND C. FERRIS. 1998. The use of molecular markers to study patterns of genotypic diversity in some invasive alien Fallopia spp. (Polygonaceae). Molecular Ecology 7: 1681-1691.
JAGER, C. 1994. Repartition, écologie et possibilités de contrôle de l'expansion de la renouée du Japon en Lorraine. Mémoire de Maîtrise, Université de Metz, Metz, France.
KIM, J. Y., AND C.-W. PARK. 2000. Morphological and chromosomal variation in Fallopia section Reynoutria (Polygonaceae) in Korea. Brittonia 52: 34-48.
LAMBINON, J., L. DELVOSALLE, AND J. DUVIGNEAUD. 2004. Nouvelle flore de la Belgique, du grand-duché de Luxembourg, du nord de la France et des régions voisines (Ptéridophytes et Spermaphytes). Jardin Botanique National de Belgique, Meise, Belgique.
LOPEZ, M. G., A. F. WULFF, L. POGGIO, AND C. C. XIFREDA. 2005. Chromosome numbers and meiotic studies in the species of Senecio (Asteraceae) from Argentina. Botanical Journal of the Linnean Society 148: 465-474.
MALLET, J. 2005. Hybridization as an invasion of the genome. Trends in Ecology and Evolution 20: 229-237.
MANDÁK, B. B. C., K. B. E. BÍMOVÁ, P. PYŠEK, J. ŠTEPÁNEK, AND I. PLACKOVÁ. 2005. Isoenzyme diversity in Reynoutria (Polygonaceae) taxa: escape from sterility by hybridization. Plant Systematics and Evolution 253: 219-230.
MANDÁK, B. B. C., P. PYŠEK, M. LYSAK, J. SUDA, A. KRAHULCOVA, AND K. B. E. BÍMOVÁ. 2003. Variation in DNA-ploidy levels of Reynoutria taxa in the Czech Republic. Annals of Botany 92: 265-272.
MARUTA, E. 1976. Seedling establishment of Polygonum cuspidatum on Mount Fuji, Japan. Journal of Ecology 26: 101-105.
MÜLLER-SCHÄRER, H., U. SCHAFFNER, AND T. STEINGER. 2004. Evolution in invasive plants: implications for biological control. Trends in Ecology and Evolution 19: 417-422.
OZKAN, H., A. AVRAHAM, AND M. FELDMAN. 2001. Allopolyploidy-induced rapid genome evolution in the wheat (Aegilops-Triticum) group. Plant Cell 13: 1735-1747.
PASHLEY, C. H., J. P. BAILEY, AND C. FERRIS. 2003. Further evidence of the role of Dolgellau, Wales, in the production and dispersal of Japanese knotweed s. l. In L. Child, J. H. Brock, G. Brundu, K. Prach, P. Pyšek, M. P. Wade, and M. Williamson [eds.], Plant invasions: ecological threats and management solutions, 197-211. Backhuys Publishers, Leiden, Netherlands.
PASHLEY, C. H., J. P. BAILEY, AND C. FERRIS. 2007. Clonal diversity in British populations of the alien invasive giant knotweed, Fallopia sachalinensis (F. Schmidt) Ronse De Craene, in the context of European and Japanese plants. Watsonia 26: 359-371.
PEAKALL, R., AND P. E. SMOUSE. 2006. GENALEX 6: genetic analysis in Excel. Population genetic software for teaching and research. Molecular Ecology Notes 6: 288-295.
PERSSON, H. A., AND B. A. GUSTAVSSON. 2001. The extent of clonality and genetic diversity in lingonberry (Vaccinium vitis-idaea L.) revealed by RAPDs and leaf-shape analysis. Molecular Ecology 10: 1385-1397.
PETIT, R. J. 2004. Biological invasions at the gene level. Diversity and Distributions 10: 159-165.
PRITCHARD, J. K., M. STEPHENS, AND P. DONNELLY. 2000. Inference of population structure from multilocus genotype data. Genetics 155: 945-959.
PYŠEK, P., J. H. BROCK, K. BÍ MOVÁ, B. MANDÁK, V. JAROSÍK, I. KOUKOLÍKOVÁ, J. PERGL, AND J. STEPÁNEK. 2003. Vegetative regeneration in invasive Reynoutria (Polygonaceae) taxa: the determinant of invasibility at the genotype level. American Journal of Botany 90: 1487-1495.
SAKAI, A. K., F. W. ALLENDORF, J. S. HOLT, D. M. LODGE, J. MOLOFSKY, K. A. WITH, S. BAUGHMAN, R. J. CABIN, J. E. COHEN, N. C. ELLSTRAND, D. E. MCCAULEY, P. O'NEIL, I. M. PARKER, J. N. THOMPSON, AND S. G. WELLER. 2001. The population biology of invasive species. Annual Review of Ecology and Systematics 32: 305-332.
SALMON, A., M. L. AINOUCHE, AND J. F. WENDEL. 2005. Genetic and epigenetic consequences of recent hybridization and polyploidy in Spartina (Poaceae). Molecular Ecology 14: 1163-1175.
SIMBERLOFF, D. 2003. How much information on population biology is needed to manage introduced species? Conservation Biology 17: 83-92.
SOLTIS, D. E., P. S. SOLTIS, J. C. PIRES, A. KOVARIK, J. A. TATE, AND E. MAVRODIEV. 2004. Recent and recurrent polyploidy in Tragopogon (Asteraceae): cytogenetic, genomic and genetic comparisons. Biological Journal of the Linnean Society 82: 485-501.
TANAKA, H. 1966. The insect visitors of Polygonum cuspidatum Sieb. and Zucc. Collecting and Breeding 28: 141-143.
TIÉBRÉ, M.-S., S. VANDERHOEVEN, L. SAAD, AND G. MAHY. 2007. Hybridization and sexual reproduction in the invasive alien Fallopia (Polygonaceae) complex in Belgium. Annals of Botany 99: 193-203.
TORIMARU, T., N. TOMARU, N. NISHIMURA, AND S. YAMAMOTO. 2003. Clonal diversity and genetic differentiation in Ilex leucoclada M. patches in an old-growth beech forest. Molecular Ecology 12: 809-818.
VANDERHOEVEN, S., N. DASSONVILLE, AND P. MEERTS. 2005. Increased topsoil mineral nutrient concentrations under exotic invasive plants in Belgium. Plant and Soil 275: 169-179.
VERLOOVE, F. 2002. Ingeburgerde plantensoorten in Vlaanderen. Brussels. Mededeling van het Instituut voor Natuurbehoud 20.
VILÀ, M., E. WEBER, AND C. M. D'ANTONIO. 2000. Conservation implications of invasion by plant hybridization. Biological Invasions 2: 207-217.
VITOUSEK, P. M., C. M. D'ANTONIO, L. L. LOOPE, M. REJMANEK, AND R. WESTBROOKS. 1997. Introduced species: a significant component of human-caused global change. New Zealand Journal of Ecology 21: 1-16.
WEBER, E. 2003. Invasive plants in the world: a reference guide to environmental weeds. CABI Publishing, Wallingford, UK.
WILCOVE, D. S. 1998. Quantifying threats to imperiled species in the United States. BioScience 48: 607-615.
ZIKA, P. F., AND A. L. JACOBSON. 2003. An overlooked hybrid Japanese knotweed (Polygonum cuspidatum Xachalinense; Polygonaceae) in North America. Rhodora 105: 143-152. 1853-1859
