Native plant species exhibit consistent drought advantage over introduced species until additional global change drivers are included: A grassland meta‐analysis

Abstract Drought is predicted to increase in frequency and intensity because of human‐induced climate change. Grassland ecosystems, many of which are water‐limited but adapted to drought, may be particularly impacted by climate change‐driven droughts. Simultaneously, invasion by non‐native species (hereafter referred to as introduced species) threatens grasslands around the world. Forecasted increases in drought occurrence are expected to alter invasion both by changing the invasibility of a system and the competitive dynamics between already established introduced species and the native plant community. Comparing the response of introduced and native plant species to drought is complex, with individual studies reporting contradictory outcomes. A synthesis across grassland systems is needed to identify consistent patterns. Understanding how introduced and native plant species respond to drought will allow us to speculate how the competitive landscape of native and introduced species may shift in grasslands under future climate scenarios. We used a meta‐analysis to synthesize results across 66 peer‐reviewed journal articles with 1205 datapoints. We found that introduced species in grasslands are, on average, 25.9% more negatively affected by drought than native species, with this pattern holding across a variety of local climate and drought conditions. Introduced woody species, in particular, tend to perform worse than native woody species under drought. Synthesis. While competitive dynamics are complex, our findings suggest that drought may shift the competitive balance in favour of native species over introduced species in grasslands. However, climate change‐induced drought will co‐occur with other global change factors (e.g. nutrient addition, grazing, elevated temperature) on grasslands. Under drought, in the context of another global change factor, native and introduced plants responded equally poorly, meaning that other global change drivers can somewhat alleviate the effect of drought on introduced species and negate the competitive advantage of native plants over introduced species.