Identifying the mechanisms underlying invasive plant establishment and native plant decline remains a central goal in ecology, particularly for biodiversity hotspots such as islands. We re-analyzed a previously published meta-dataset to test the prediction that neighbor effects are stronger on islands vs. continents because island plants are weaker competitors. Although we detected marginally stronger neighbor effects on islands than continents, this was due, at least in part, to stronger competition among native species. An absence of studies testing neighbor effects between native vs.invasive plants on islands prevents a rigorous test for competition effects on islands, highlighting an important knowledge gap. K E Y W O R D Sisland rules, meta-analysis, neighbor effects, plant invasions