Proceedings of the National Academy of Sciences of the United States of America | 2019
Adaptational lag to temperature in valley oak (Quercus lobata) can be mitigated by genome-informed assisted gene flow
Abstract
Significance Forested ecosystems provide many ecological, economic, and societal benefits, but those benefits are threatened by climate change. Conservation strategies often assume that plants are currently growing in conditions well-suited to their growth, survival, and reproduction, regardless of whether this assumption is valid. We show that an ecosystem-foundational species in California, valley oak (Quercus lobata), is already mismatched to current temperature and will likely experience further declines in growth rates as temperatures rise over the next century. Given this mismatch, new approaches to climate change management are needed. By using genomic information and identifying genotypes with faster growth rates under warmer temperatures, we present an approach to mitigate negative consequences of rising temperatures for species that may already be experiencing maladaptation. Climate change over the next century is predicted to cause widespread maladaptation in natural systems. This prediction, as well as many sustainable management and conservation practices, assumes that species are adapted to their current climate. However, this assumption is rarely tested. Using a large-scale common garden experiment combined with genome-wide sequencing, we found that valley oak (Quercus lobata), a foundational tree species in California ecosystems, showed a signature of adaptational lag to temperature, with fastest growth rates occurring at cooler temperatures than populations are currently experiencing. Future warming under realistic emissions scenarios was predicted to lead to further maladaptation to temperature and reduction in growth rates for valley oak. We then identified genotypes predicted to grow relatively fast under warmer temperatures and demonstrated that selecting seed sources based on their genotype has the potential to mitigate predicted negative consequences of future climate warming on growth rates in valley oak. These results illustrate that the belief of local adaptation underlying many management and conservation practices, such as using local seed sources for restoration, may not hold for some species. If contemporary adaptational lag is commonplace, we will need new approaches to help alleviate predicted negative consequences of climate warming on natural systems. We present one such approach, “genome-informed assisted gene flow,” which optimally matches individuals to future climates based on genotype–phenotype–environment associations.