We have studied the genetic diversity of three plant species: Angelica archangelica (Apiacieae), Bistorta vivipara (Polygonaceae) and Viscaria alpina (Caryophyllaceae) along the free-flowing Vindel River in northern Sweden. The plants differ in reproductive strategy. A. archangelica and V. alpina are insect pollinated outbreeders while B. vivipara reproduces with apomixis through bulbils. The seeds of A. archangelica may float for over a year, while the propagules (seeds and bulbils, respectively) of V. alpina and B. vivipara float for less than two days. Genetic diversity was assessed using starch gel electrophoresis. The clonal diversity of B. vivipara measured by Simpson's index (D) ranged between 0.78 and 0.99. Only a few clones were shared between localities. The average percentages polymorphic loci and mean He based on polymorphic loci for V. alpina over all localities were 23.1 and 0.15, respectively. Wright's F-statistics showed a significant overall deficit of heterozygotes. The diversity of A. archangelica was found to increase downstream. Genetic diversity of each species is sufficiently high to be used in studies on hydrochory. Dispersal appears to be related to the floating ability of progagules.