The use of molecular markers to study patterns of genotypic diversity in some invasive alien Fallopia spp. (Polygonaceae)

Random amplified polymorphic DNA (RAPDs) and inter-simple sequence repeats (inter-SSRs) have been used to study clonal growth and hybridization in some non-native, gynodioecious, invasive weeds from the genus Fallopia (Polygonaceae). At the study site (the River Kelvin, Glasgow, UK) a single genotype of Japanese knotweed ( Fallopia japonica ) was detected, consistent with all the individuals sampled being ramets of a single clone. Two genotypes of giant knotweed ( F. sachalinensis ) were detected, with one genotype accounting for all but one of the samples, again indicative of widespread clonal growth. Five genotypes of the hybrid between Japanese and giant knotweed ( F. × bohemica ) were recovered. F. × bohemica is the only male-fertile taxon present at the site and it seems probable that at least some of this genetic variation is attributable to hybrid fertility. A single plant identified using morphological methods as a backcross between F. japonica and F. × bohemica was analysed, and the molecular data were consistent with this theory. A comparison of RAPDs and inter-SSRs showed that the two techniques gave data that are broadly congruent, and both techniques showed a similar sensitivity in the number of genotypes detected.