| Invasive exotic species are a recognized threat to native ecosystems because they lower biodiversity and change community and ecosystem processes. There are many theories concerning how a non-native species becomes established and out-competes native species. This study investigates the ability of one invasive, Iris pseudacorus, to more efficiently assimilate resources and produce more biomass than a native congener, I. hexagona , in the same environment. I. pseudacorus is native to Eurasia and can be found across a broad range of habitats in both fresh and brackish water. Its habitat preferences and environmental tolerance overlaps I. hexagona, which is native to wetland habitats in the Lower Mississippi River Valley and the Gulf Coast of North America. Although it has become a pest in much of North America since its introduction in the 1800s and is widely planted in horticultural settings in Coastal Louisiana, a field survey presented here shows that it has not yet become a threat to wetland habitats in the area. The experimental studies explore the establishment and growth capabilities of both seed and rhizome propagules in fresh and salt water, as well as the effects of multiple stressors including temperature and salinity on the performance of the invasive relative to the native species. Data from all studies support the hypothesis that I. pseudacorus may be experiencing a lag time in the invasion process along coastal Louisiana. We also found that freshwater populations can be expected to thrive in Louisiana while brackish water populations are expected to maintain a low population and persist without threatening the native ecosystem. |
