Earlier phenology of a nonnative plant increases impacts on native competitors

Significance Adaptation to climate can promote the spread of nonnative species, but its wider impacts on native species have rarely been studied. Prickly lettuce ( Lactuca serriola ), an annual plant that has been introduced from Europe around the world, flowers earlier in arid climates such as those of southern California. By comparing L. serriola populations differing in flowering time within common garden experiments, we demonstrated that native California annual plants experienced stronger competition from the local early flowering L. serriola than later flowering plants from the ancestral European range, making their predicted persistence with L. serriola more difficult. Our study suggests that climate adaptation can have cascading effects on ecological communities, potentially increasing the impacts of biological invasions.