Using climate-driven adaptive evolution to guide seed sourcing for restoration in a diverse North American herb-shrub species

Seeds zones are bounded geographic areas to guide seed sourcing for landscape scale restoration. Yet seed zones based on plant adaptative traits are lacking for most restoration species. Sulfur-flower buckwheat (Eriogonum umbellatum Torr) includes herbs, subshrubs, and shrubs adapted to a range of ecological regions within North America. Its widespread occurrence and diversity make it a suitable model species to explore seed zone development based on evolutionary plant adaptations. Within a common garden, 69 populations from diverse seed sources and 13 taxonomic varieties were evaluated for 17 phenological, morphological, and production traits in 2016 and 2017. Analyses of variance showed taxonomic varieties and seed source locations differed for all plant traits. Linear correlation revealed source locations with warmer mean temperature and more precipitation generally had later phenology, larger umbels, more leaf area, higher leaf dry weight, and more seed and shoot dry weight production. Canonical correlation strongly linked seed source climates at source locations with plant traits evaluated in the common garden, suggesting climate-driven adaptive evolution. Canonical variates 1 and 2, explaining 60% of the variation, were used to develop regression models that predicted their values from climate variables across the study area. Using geographic information technology these were mapped into 12 seed zones representing 1.31 million km(2) in the Western United States. These zones were designed to provide guidance to practitioners when sourcing sulfur-flower buckwheat for restoration projects. We expect this methodology can be successfully applied to other species to develop seed zones based on adaptive evolution.