For colonization success, should hosts and microbes travel alone, together, or swap partners along the way?

Understanding what determines colonization success is a key challenge of global change ecology. Microbiomes that enhance host performance are likely to be co-introduced with hosts during colonization due to their intimate association. Yet, it is unclear how co-introduced microbes will impact host colonization, as both the microbiome and its effects could vary upon introduction into a new habitat. Here, we used duckweeds —a cosmopolitan, freshwater angiosperm— and their microbiome to track colonization dynamics during an experimental co-introduction in the wild. Notably, we found that host performance was substantially reduced when plants were co-introduced with microbes non-local to the introduced habitat, relative to hosts with a local microbiome. Moreover, negative impacts from the non-local microbiome persisted for multiple host generations despite a rapid turnover in microbiome composition during colonization. Overall, we suggest that considering the co-introduced microbiome can help predict host colonization success under global change.