Rapid evolution can contribute to species’ responses to changing climates, both for native species experiencing climate change and for non-native species spreading in a new region. Whilst the benefit for the evolving species is normally clear, the wider implications for the community with which it interacts are less well understood. For example, evolution could tend to reduce the potential for coexistence if it contributes to greater fitness inequalities among competitors, or promote coexistence by increasing niche differentiation. Evolution could therefore influence the impacts that non-native species have on the communities they invade, and also shape community structure following climate change.
Lactuca serriola is an annual plant native to Eurasia, which has a global distribution and has evolved its flowering phenology as it spread along climate gradients in its new range. We combined field experiments with coexistence theory to ask how the evolution of phenology in Lactucahas affected its potential for coexistence with a novel native plant community in California. Knowledge of the introduction history of this species makes it possible to demonstrate the impact of evolution on competitive outcomes by comparing ancestral and descendent populations.
Lactuca populations originating from different climates varied greatly in their phenology in a common garden in California. Populations from the regions with the warmest climate, including the local non-native population from California, bolted and flowered earlier than those from cooler climates from the native range – except for a few individuals, plants from the population originating from the coolest climate (Switzerland) failed to bolt at all. Variation in phenology affected the ability of Lactuca to suppress native competitors, with early flowering plants exerting a much stronger competitive effect on native species than late phenology plants (from native range). This suggests that evolution of phenology during invasion reduced the potential for native and introduced species to coexist. As well as affecting the outcome of interactions among native and non-native species, we might therefore also expect evolution to influence the outcome of interactions among resident and range-expanding species under a changing climate.