Assessing Stream-Mediated Seed and Shoot Dispersal of Invasive Plants in an Urban Riparian Wetland

Résumé du livre

Ruellia simplex and Tradescantia fluminensis were introduced to Florida and elsewhere and are now considered invasive plants. Millions of dollars are spent annually on the control of invasive plants in Florida alone. The goals of this study were to determine the importance of stream dispersal in invasive plants such as R. simplex (by seed) and T. fluminensis (by shoots) in riparian wetlands. The 13,269 seeds and 179 shoots intercepted during net deployments in a Florida stream included 131 seeds and 20 shoots of R. simplex and 6 shoots of T. fluminensis. Net verification tests showed low retention of R. simplex seeds while retention of T. fluminensis shoots was 100%. The low seed retention values for R. simplex suggested that the actual number of seeds transported downstream during net deployments may have been in the thousands. Numbers of propagules per year transported downstream are estimated at 18,000 to 30,000 R. simplex seeds, 8,000 to 10,000 R. simplex shoots, and 2,000 to 8,000 T. fluminensis shoots. Capture rates of marked propagules showed mobility to be low for R. simplex seeds but high for T. fluminensis shoots. Ruellia simplex seeds are negatively buoyant while T. fluminensis shoots are somewhat positively buoyant but become negatively buoyant within 15 days of submergence. Percent germination of net-captured R. simplex seeds was 6.9% in a germination chamber and 21.8% inside a glasshouse. Survivorship with growth of net-captured shoots amounted to 22.2% for R.