Warming conditions reduce the impacts of an aquatic invasive macrophyte across a latitudinal gradient

Abstract Climate change and biological invasions represent two of the most important drivers of global ecological change. While the ecological effects of each have been extensively studied, there is limited empirical research evaluating how they are likely to interact with each other. Multiple mechanisms have been hypothesized that could lead to synergistic interactions between climate change and invasions. Tests of these interactions have been focused on small scale mechanistic studies or ecological niche models which generally ignore the role of species interactions with a complete native community. In situ studies are critical for incorporating these interactions but have been limited because of logistical challenges. To empirically assess the potential effects of climate change on invasions of Nitellopsis obtusa , an invasive freshwater macroalga, we established monitoring sites across a latitudinal gradient as a proxy for future climate change. We then monitored peak annual biomass, benthic cover and seasonal phenology over multiple years to assess if climate conditions influenced N. obtusa invasion dynamics. Populations of N. obtusa were significantly negatively correlated with temperature in terms of both biomass and benthic cover and we observed an advancement of seasonal phenology in warmer years. Benthic cover of native plants increased with warmer winter temperatures. Synthesis . Together, these results suggest that native communities, potentially because of the broader range of trait diversity represented across multiple species, may be more resilient to shifting climate conditions than N. obtusa . As a result, there could be an antagonistic, rather than synergistic, interaction between climate change and N. obtusa invasion.