Greater performance of introduced vs. native range populations of Microstegium vimineum across different light environments

Non-native plant invaders may undergo evolutionary changes through founder effects, hybridization, adaptation to novel environments, or other processes. Genetic changes in introduced populations may promote invasiveness by increasing plant vigor and plasticity. To determine if introduced populations of the annual grass Microstegium vimineum exhibit greater growth than populations from the native range, we grew plants from 10 native (China) and 10 introduced (U.S.) populations in the greenhouse under two light environments and evaluated growth and morphological traits across two harvest dates. Microstegium from introduced populations had on average 50% and 35% greater biomass in the shade and sun, respectively, than native populations at the first harvest and 59% and 33% greater biomass by the second harvest date. We found no difference in plasticity for growth across the light treatments between native and introduced populations. There were significant morphological differences in resource allocation with native populations producing greater leaf area and leaf mass per stem mass than introduced populations. However, introduced populations produced more biomass overall, despite lower allocation to leaves, which suggests greater efficiency of photosynthesis or lower respiration. These results demonstrate significant genetic differences between introduced and native populations of Microstegium for growth and morphological characteristics. Evolution of Microstegium and other introduced species may complicate the prediction and management of biological invasions.