Species with shared geographic history may co-evolve, with interactions leading to niche differentiation and improved resource capture. Thus, plant communities assembled from sympatric sources (shared geographic origins) are predicted to be more productive and invasion resistant than those from allopatric sources (different origins), even with identical species composition. We compared performance among communities of four species from 15 locations, assembled from allopatric or sympatric sources. Unexpectedly, allopatric-sourced communities had 29-35% more inflorescences, 19% higher survival, 19% longer growing season, 26-53% greater size, and 108% lower invader biomass than sympatric-sources. Sympatric populations showed trait convergence consistent with strong environmental selection, with trait variation higher in allopatric communities. Variation was associated with higher productivity and invasion resistance, suggesting an advantage of allopatric sources for community reassembly when environmental filters are strong. These findings challenge assumptions about the advantages of shared origins and have implications for understanding competition, community assembly, and ecosystem restoration.