Natural selection for resistance to the allelopathic effects of invasive plants

1 Exotic plant invasions often cause high mortality in native populations and therefore have the potential to be a powerful selective force. 2 We found that surviving individuals from North American communities that have experienced extensive invasion by Centaurea maculosa have higher tolerances to the Eurasian invader than individuals from communities that did not experience invasion. 3 Some native species grown from the seed of individuals that survived Centaurea invasion were more resistant to the general competitive effects of Centaurea, the root exudates from Centaurea, and to a chemical specific to the root exudates of Centaurea (+/-)-catechin. 4 Although these results may be confounded by maternal effects, they provide initial evidence that native plant species may evolve to tolerate the effects of an exotic invader, and in particular an invader's novel allelochemistry. 5 Such effects may have long-term implications for plant invasions and the organization of plant communities. Evolved tolerance may ultimately contribute to coexistence among natives and invaders, with our results suggesting that natural plant communities may be more coevolved and less individualistic than currently thought.