Hydrochory, population dynamics and distribution of the clonal aquatic plant Ranunculus lingua

The dispersal and dynamics of the clonal aquatic plant Ranunculus lingua were studied in a marginal river population in northern Sweden, where this species is dispersed exclusively by vegetative diaspores (i.e. floating rhizome fragments). The study focused on (a) the extent and range of dispersal, (b) relationships between dispersal and distribution of established stands of R. lingua, and between dispersal and environmental characteristics of the river (i.e. 'river status'), (c) the establishment success of vegetative diaspores, and (d) the relative changes in ramet numbers between years. Between 0.8 and 2.9% of the total population of ramets was estimated to disperse each year. Most rhizomes were dispersed within 1.5 km in a leptokurtic pattern. A river lake functioned as a dispersal barrier, preventing dispersal distances greater than 3 km. Vegetative diaspores were mainly dispersed to river curves and obstacles, and the distribution of established stands was highly correlated with these features. Establishment was low and probably strongly influenced by water-level fluctuation and winter conditions. Relative changes in ramet numbers varied between years and were correlated with water-level fluctuations during the present and previous growing seasons, with winter low-water, and with duration of spring-flood. The predictability of change was high within but low between stands.