An inventory of adaptive genomic diversity of Joshua tree (Yucca brevifolia sensu lato)

Joshua tree, an iconic keystone species of the Mojave Desert, is expected to see dramatic reductions in its suitable habitat under projected climate change. The trees are unlikely to be able to migrate to track more suitable climates, but they encounter a range of extreme climatic conditions across their existing range, and populations may harbor genetic variation that could support adaptation to changing climate. Knowledge of genetic variants that predict Joshua tree adaptation to particular climates could help to identify such populations and prioritize them for protection, and could inform conservation projects to restore Joshua tree populations by matching seed sources to projected future climates. While we have led efforts with Mojave regional conservation organizations to produce a complete reference genome (the Joshua Tree Genome Project, JTGP), a comprehensive genomic inventory of natural Joshua tree populations is lacking. Here, we propose whole-exome sequencing of 300 Joshua trees across the species? range. We will closely work with JTGP collaborators, including USGS, and conservation partner organizations, to strategically sample populations attending to density, phenotypic and climatic diversity, and areas of especial conservation concern. The resulting genomic dataset will be the first large-scale sequencing of a keystone desert species. This will likely enable discovering new genes related to the evolution of extremophile plants, allow us to map genetic variants for climate adaptation, and predict climate change susceptibility of extant natural Joshua tree populations. The scope and scale of this work would serve as a model for genetically-informed desert species conservation. We will make the resulting dataset readily available via the NCBI Sequence Read Archive, and as a core element of a developing public database built by the JTGP to inform conservation of Joshua trees. We propose a genetic inventory of Joshua tree populations that can predict populations? adaptation to current and future climates.