The Success of an Invasive Poaceae Explained by Drought Resilience but not by Higher Competitive Ability

Abstract Invasions are occurring very rapidly and they may be enhanced by alterations associated with climate change. Environments exposed to stronger droughts (supposed to occur in some regions in response to climate change) may become more susceptible to the invasion of certain species of plants. We experimentally measured the recovery of a native (Hymenachne pernambucensis) and a non-native invasive (Urochloa arrecta) macrophyte to extreme drought, and we evaluated whether the interspecific competition is affected by the drought stress or not. We found that the invasive species recovered biomass from drought more efficiently than the native species when they grew in monocultures. In contrast, the data of aboveground biomass showed that the invasive species was more negatively affected by interspecific competition than the native one. These results indicate that the invasive species is more resilient to droughts than the native, but the native species has a greater competitive ability than the invasive. Thus, the high dominance of U. arrecta observed in several aquatic ecosystems can be explained by its resilience to drought disturbances. Our findings also demonstrate the importance of biotic resistance since the invasive species does not grow well in the presence of native neighbors.