The contribution of seeds and turions towards population growth and persistence of Hydrocharis morsus-ranae L.

This thesis presents the result of a study that examined the relative contribution of seeds and turions towards the population growth of Hydrocharis morsus-ranae L. (Hydrocharitaceae), a free-floating invasive aquatic macrophyte. A lifecycle study was conducted, that compared propagules at the following stages: production, germination, recruitment, and growth. Standing crop/m$\backslash sp2$ was a significant variable that explained the pattern of production, and the results contradicted earlier models. Propagules had different germination rates after various storage and growing treatments. Approximately, 26% of turions were recruited compared to only 0.0002% of seeds in the field. A growth experiment indicated that the high relative growth rate of seedlings does not produce a larger plant. Instead, larger turions were able to produce larger plants than were smaller turions and seeds. A model was produced which predicted that seedling contribution to the adult population is minute, (0.0002%) because of low recruitment, survivorship and growth.