Phenotypic variability in native populations of Lythrum salicaria L. across geographical gradient:: between and within population differences.

The study deals with the variability and changes in growth characteristics in native populations of Lythrum salicaria L. across a geographical gradient. Plants from 15 populations originating from Sweden, Poland, Slovenia and Israel were cultivated in a garden experiment. Plant height, total plant mass and their components (dry weight of shoots, roots, lateral branches, leaves and inflorescence) as well as other plant growth characteristics (basal stem diameter, number of lateral branches and internodes etc.) were investigated at the end of the first growing season. The greatest proportion of total variability between the populations in plant height, aboveground shoot dry weight, dry weight of lateral branches, leaves and inflorescences, as well as basal diameter, leaf area, specific leaf area, flowering time and number of primary lateral branches can be explained by differences in latitude of geographical locations from which the populations originated. In some instances, variability in root dry weight, number of roots and number of internodes was higher both between and within the populations than between the geographical locations. Most of the growth characteristics, except for the number of roots, flowering time and number of internodes were well correlated with latitude of the plants' original location. This suggests that a natural gradient exists in phenotypic variability of L. salicaria within its native range.