Collaborative Research: Linking phenotypes and genomes to environmental maladaptation in two contrasting oak species

Oaks dominate many ecosystems of California and the United States, making them crucial to biodiversity and economically valuable for timber products, such as lumber and furniture wood. Recent research has demonstrated that oaks are maladapted to current environmental conditions, being better adapted to cooler environments present 20,000 years ago. This unexpected maladaptation results in tree mortality, reduced growth, and increased susceptibility to pathogens. The project investigates the understudied concept of oak maladaptation by linking physiological traits, tree performance and fitness, and genomics. This project will investigate two widespread, ecologically important California tree oak species--Quercus lobata (valley oak) and Q. agrifolia (coast live oak)--which often grow together, but have different physiological responses to temperature and drought. Project goals are to understand how physiological traits determine tree growth, survival, and reproduction, whether these traits are genetically based, and how the underlying genetic gradients across the landscape can be used to predict which tree populations are most vulnerable and which are most resilient. Findings will both inform management strategies for oak restoration and conservation in areas where oaks have been removed by harvest or wildfire and also provide a case study for other forest tree species. The research will enhance the STEM workforce by educating students and postdoctoral scientists in cutting edge concepts and tools in integrative biology, ecology, evolution, and forestry. This project is an integrative study of the mechanistic and fitness response of trees to their environments using the understudied but ubiquitous phenomenon of maladaptation. Trees are particularly vulnerable to maladaptation due to their long generation time and long life span that can result in individuals being out of sync with current environments. Through these two contrasting California oaks, the project will first identify the physiological traits associated with response to high temperatures and drought through greenhouse and field experiments. Second, the studies will see whether traits contribute to the survival and growth across a tree’s life history of seedlings, saplings, and young adult trees, and determine how much key traits are genetically based. Third, a landscape genomic study will be conducted to identify geographic regions of maladaptation for each species based on genomic markers, and test whether these areas are the same as predicted to show maladaptation using empirical findings from physiological and fitness studies. This information can be used to identify seed sources for restoration and management of oak projects. This research will address the knowledge gap between selective processes and mechanisms affecting adaptation versus maladaptation. It will also demonstrate the innovative use of landscape genomics tools to detect maladaptation across a species range. By linking phenotypic mechanistic findings and relative fitness of trees with genomic information, this project will demonstrate how functional genomics can inform tree conservation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.