Genotypic and phenotypic variation in a Fallopia × bohemica population in north-eastern France.
The Japanese knotweed s.l. population of a riverine region of north-eastern France was examined for a variety of ecological and genetic parameters. The population was dominated by the hybrid Fallopia × bohemica, but the population was morphologically variable and unusual in its being comprised entirely of hermaphrodite 6× and 8× F. × bohemica plants, plus a single aneuploid adult. Chromosome counts are given, and these indicate that both aneuploid and euploid individuals are being produced and becoming established in the study area. It was also found that all plants examined had the F. japonica var. japonica chloroplast haplotype. Based on differences in morphology and phenology, the clones were divided into four main categories (1 to 4). Category 1 was widely distributed (nearly 90% of the area) with the other 3 being of more restricted occurrence. Category 1 produced little seed and was not the tallest plant nor the clone with the fastest growth. The other categories all produced seed and grew faster. From these results, we can conclude that from an ecological point of view, some clones are more aggressive than others with a similar chromosome composition. Aggressiveness can be linked to the absence of seed production and possession of large leaves, which might allow higher storage of nutrients and greater volume of rhizome in the soil.