16Evolution might mitigate negative effects of environmental change on diversity by rescuing 17 populations from extinction. However, biotic interactions could affect adaptation to abiotic 18 change, and conversely, adaptation to an abiotic stressor could influence biotic interactions. 19We used experimental evolution of microalgae to investigate reciprocal effects of competition 20 and adaptation to salt stress. We found that evolutionary history influenced competitive 21 interactions and community properties. In high-salt environments, communities assembled 22 from lines with a history of salt stress declined more slowly in diversity than communities 23 assembled from lines without prior exposure to salt. We also found that a history of salt stress 24 can lead to reduced competitive ability in the ancestral environment. While competition had 25 no effect on adaptation to salt, we found that competition can hinder evolutionary rescue by 26 preventing that adaptation translates into population persistence. Collectively, our results 27 highlight the importance of considering evolutionary rescue in a community context. 28