Considering ploidy when producing and using mixed‐source native plant materials for restoration

There is a clear need to maximize the genetic diversity of plant material used in restorations to ensure restored populations are equipped to handle current and future conditions. This increasingly translates to focused efforts to intentionally increase the genetic diversity of seed sources in production and/or restoration settings. For example, multiple populations may be brought together to create plant materials with more genetic diversity than is present in any single population. Recent literature showing minimal risk of outbreeding depression and extensive benefits of genetic rescue has helped justify this approach, with the exception of mixing populations with fixed chromosomal differences. In these cases, extensive loss of fertility may occur after mixing. Some types of incompatible chromosomal differences are difficult to detect and therefore have unknown occurrence and distribution within and among species. However, the most extreme form of chromosomal differences—intraspecific ploidy variation (IPV)—is relatively easy to quantify with current technology and known to be fairly common in angiosperms. To encourage more systematic consideration of IPV in native plant restoration, we used available data on IPV to estimate its incidence in 115 species widely used for restoration in the United States. Over one‐third have IPV. Additional focused research is needed to understand the consequences of IPV for restoration, particularly given the current trend toward mixing natural collections for materials development and use. We provide recommendations to explicitly incorporate the reality of IPV into the production and use of genetically diverse plant materials for restoration.