Success of coastal sage scrub restoration is influenced by local adaptations of shrub species.

PREMISE: Restoring plant communities is increasingly challenging with climate change. While practitioners have traditionally used local seed sources, many are recommending assisted migration, possibly from more extreme environments such as inland rather than coastal environments, for restoration. METHODS: We compared the performance of four dominant Southern California shrub species, grown from seed from either coastal (mean 17.11°C) or inland (mean 19.28°C) populations, in a coastal common garden site under three levels of water availability. The goal was to test whether inland populations had higher survival, growth, and reproduction than coastal populations when experiencing the extreme highs and lows of water availability currently observed inland that mimic possible future climate conditions in coastal regions. RESULTS: Plants of most species generally grew less and had fewer flowers with water reduction, but neither flowering nor growth were strongly or consistently affected by seed source. Within our coastal common garden site, survivorship of coastal-sourced plants was higher than survivorship for inland-sourced plants. An interaction between seed source and water treatment influenced survivorship of all species, such that the negative effect of decreased water was more pronounced for inland-sourced plants. This effect might be explained by the physiological trait measurements which indicated stomatal conductance of Eriogonum and Salvia was higher for inland-sourced populations, suggesting increased water use. CONCLUSIONS: Collectively, these findings indicate that the dominant shrub species in this coastal Mediterranean ecosystem are sensitive to reduced water, and assisted migration from inland to coastal environments will not improve restoration outcomes.