Wetland habitats are besieged by abiotic and biotic disturbance such as invasive species, fragmentation, and salinization. Predicting how these forces will alter local population dynamics and community structure is a central challenge to ecologists. Using stage-structured matrix models, we examined the potential effects of abiotic disturbance on native blue (Iris hexagona) and invasive yellow (Iris pseudacorus) iris populations. Iris is an ideal model for testing these questions because of its clonal/sexual mating system and tolerance of diverse wetland conditions; comparing ecologically comparable iris congeners can help elucidate key life-history traits underlying demographic responses.
Results/Conclusions
Our models, parameterized with empirical data and field observations, predict dichotomous responses of native and invasive iris to salinity stress. Colonization of freshwater or brackish habitat by both species rarely led to coexistence. In 66% of freshwater marsh simulations, invasive iris populations excluded the native within 50 years. However, in 96% of brackish marsh simulations, the native species excluded the invasive within 25 years. Coexistence of species only occurred when we introduced periodic hurricane salt pulses into the freshwater marsh. Our results indicate that abiotic disturbance can limit the spread of invasives in some circumstances. As disturbances such as invasive species and salinization of habitat become more widespread, modeling can become a valuable tool in managing critical habitats and plant communities.
