Abstract: Plants must rely on phenotypic changes to the environment, local adaptation, or migration to survive the changing climate and loss of suitable habitat due to development. Human interventions, such as habitat restoration and assisted migration can help ensure the survival of plant species, but their success is dependent on knowledge on the ability of the chosen individuals to survive in future climate conditions. Unfortunately, this information is not available for many species. Here we explore the extent of local adaptation and phenotypic plasticity in Heteromeles arbutifolia, toyon, an iconic chaparral species endemic to and widely distributed across the California Floristic Province. Individuals sampled from across the range display large phenotypic variation raising the question of whether the individuals are locally adapted to the widely varying environments in which it lives or if individuals are phenotypically plastic. To address these questions we collected leaves from 296 plants as well as seeds from 40 individuals, a subset of the total, capturing toyon’s geographic range in California. We germinated seeds, grew them in a greenhouse, and then outplanted at two experimental gardens: one at the northern and one at the southern part of toyon’s range– Blue Oak Ranch Reserve in San Jose, CA and Stunt Ranch Reserve in Calabasas, CA – to determine if individuals were adapted to their local conditions. We analyzed variation in seed size, germination time, growth rate, branching patterns, survivorship, and leaf morphology across the geographic range correlated with climatic variables sourced from the WorldClim data source, finding expected trends correlated with climate variables, but that only toothing pattern is genetically inherited. Survivorship in the southern location was much lower than in the northern garden, but maternal lines did not differ in survivorship. We also did not observe differences between maternal lines in leaf shape, size, and growth rate, but we did observe differences between the two gardens. The variation we observed was due to plastic differences in measured traits, thus the environment from which seeds were sourced does not impact their chances of survival or phenotype. Since plasticity is the main driver of phenotypic differences between individuals sourced across toyon’s wide range in the California ecosystem, conservation managers can be confident that the source of seeds for restoration projects will have little effect on the success of their restoration.
