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

Abstract

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.Key words: chromosomal differences, genetic diversity, intraspecific ploidy variation, mixed-source native plant materials development and use, outbreeding depression Implications for Practice• Intraspecific ploidy variation (IPV) was found in one-third of 115 common restoration species in the United States, highlighting the importance of incorporating it in restoration sourcing decisions.• For species with IPV, declines in seed set and offspring fitness are likely when populations with different ploidy levels are planted together. To minimize these negative consequences for species with known or suspected IPV, the ploidy of populations being considered for mixing should be investigated using flow cytometry, and individuals with different cytotypes should not be mixed in production beds or restoration settings.• If IPV is suspected but not known for all populations being mixed, small trial plots should be used to identify and mitigate potential fitness consequences before mixing over large scales.

Intraspecific variation mediates density dependence in a genetically diverse plant species

“…Newly arisen tetraploid recruits in diploid neighborhoods face genetic (Kramer et al. 2018), demographic, and ecological establishment constraints (Rodriguez 1996, Fowler and Levin 2016); thus, high tolerance to competition from neighboring plants may be critical for their establishment. Our results demonstrate greater neighborhood tolerance in tetraploid plants across a range‐wide gradient of environmental conditions.…”

Collection and production of native seeds for ecological restoration

“…For taxa with known polyploidy, such as many grasses, it is important (where possible or where the information exists) to determine the ploidy number of the potential source populations and avoid establishing seed production plots with seed from multiple populations with different ploidy levels, because the seed produced by cross fertilization will not produce fertile plants and thus would not persist in restoration plantings (Kramer et al ).…”

Intraspecific Variation in Plant-Plant Interactions and Belowground Zone of Influence of Big Sagebrush (Artemisia tridentata)

“…Specifically, A.t. tridentata:4x had higher neighbor tolerance compared to its diploid variant when the effect on the latter was observable. In agreement with other studies (Hahn et al, 2012;Maceira et al, 1993;Schlaepfer et al, 2010), polyploids generally have higher competitive capacity as young recruits are likely to face competition from established populations of diploid plants (Rodriguez, 1996) or extensive loss of fertility (Kramer et al, 2018). Accounting for neighbor interactions in space explicitly will provide insights into evolutionary origins and mechanisms of polyploidy in plant species.…”