Population genomic & trait diversity assessment of a common shrub highlights the importance of species-specific data for restoration seed sourcing.

Planting native species to restore ecological function is a key ecosystem conservation strategy. Increased impacts from human and climate disturbances can make restoration from seed fail more often, making seed source selection an increasingly important consideration. However, selecting appropriate plant materials for successful ecological restoration can be challenging. Seed sourcing for rapidly establishing, self-sustaining native plant communities is complicated by the fact that not all seed sources are equal. Understanding genetic and trait diversity between different seed source collections is important for seed selection and project outcomes. Here, we investigate population genomics and variation in performance traits, as measured in a common garden, of a widely distributed sub-shrub, Artemisia frigida Willd. (fringed sage), that is commonly used in grassland restoration. Our results show population genetic structure, albeit relatively weak (max pairwise FST<0.1), across 11 focal seed source collection sites in the U.S. Mountain West. Variation in genomic loci and traits both showed some alignment with geography that could be clustered into three groups; the genotypic and trait groups are distinct with some overlap. We provide an example of how genotypic and trait diversity support relaxing provisional seed zone recommendations, which divide the focal populations into 6 groups. We also provide a counter example where our genomic analysis identifies a distinct genetic cluster, which would be lumped based on provisional seed zone guidance, but distinguished based on ecoregion. We highlight the value of species-specific data for restoration seed sourcing, while also providing insight into the benefits and drawbacks of using provisional seed zones when species data is lacking.