Abiotic forces such as salinization and hurricanes threaten the ecology and function of Louisiana coastal ecosystems. In addition, biotic factors such as invasive species can dramatically alter these endangered communities. My study examines some abiotic and biotic forces that affect the seed ecology of native and invasive plant populations in coastal Louisiana. Iris hexagona, a Louisiana native, is widespread throughout Louisiana's wetlands. Iris pseudacorus is an invasive exotic in 43 of the lower 48 states. Both species are freshwater plants tolerant of salt water conditions. Although present in Louisiana, I. pseudacorus is not currently listed in the state as an invasive species. In order to predict the potential success of I. pseudacorus and prevent its expansion into natural areas, we need to understand its reproduction and dispersal abilities. Both the native and invasive species disperse via hydrochorous seeds, thus their successful germination and establishment depends on environmental conditions. I conducted experiments to investigate how dispersal via floatation might affect germination of I. hexagona and I. pseudacorus seeds. Preliminary results indicate that native iris seeds can remain afloat for much longer periods than I. pseudacorus seeds. However, the invasive seeds germinate much more rapidly during floatation, and form dense root and leaf mats on the water surface. These distinctly different dispersal mechanisms could have profound implications for colonization, habitat exploitation, and population persistence.
