Assessing global trends, biases, and knowledge gaps in research on ecological interactions in goldenrod (Solidago spp.) invasions

North American goldenrods ( Solidago spp.) rank among the most ecologically impactful invasive plants in Europe, Asia, and other regions. Their spread is driven by high ecological plasticity, rapid growth, and allelopathic effects. While the number of publications on Solidago invasions has grown substantially in recent decades, existing reviews tend to be narrative and focus on single species or few mechanisms. In this systematic review, we analyze 180 peer-reviewed empirical studies to assess global trends, methodological approaches, and research biases in studies addressing interactions between invasive Solidago and the environment. Most studies applied a single methodological approach, with ex situ experiments dominating, while field observations and in situ manipulative experiments were less common. Long-term studies were rare, and research primarily addressed current conditions rather than future scenarios. The taxonomic focus was centered on S. canadensis L., with other species being much less studied. Geographically, research was concentrated in Europe and Asia, with field-based studies more common in Europe and ex situ experiments dominating in Asia. Solidago spp. served as either a response or an explanatory variable, reflecting both its response to environmental conditions and its impact on the invaded ecosystem.