Genetic variation and structure change when producing and using mixed‐source seed lots for restoration

Abstract

Large-scale ecological restoration efforts increasingly require large quantities of genetically diverse seeds adapted to a range of potential sites. To meet this demand, there is a growing emphasis on mixing multiple, regionally sourced source populations in production settings to produce large quantities of genetically diverse seeds. However, because few empirical studies are available, it is unclear how source population representation and genetic diversity shift through production and restoration use of mixed-source seed lots. We used neutral genetic markers and assays of variation in seed germination requirements to investigate how genetic diversity and source population representation shift following the use of a mixed-source seed lot to establish a seed production field and 10 restoration sites. Our mixed-source seed lot contained 19 source populations of the perennial forb, Penstemon pachyphyllus, from six mountain ranges in the Great Basin, U.S.A. We found that, while populations from all six mountain ranges used in the mixed-source seed lot were present in production and restoration sites, representation of each source mountain range shifted unpredictably. Populations from one mountain range were particularly overrepresented at the production site relative to its composition in the original seed mix. We also found that, despite using the same mixed-source seed lot for production and restoration sites, resulting source population composition varied greatly, suggesting that local conditions favored some populations over others. Significant among-population variation in seed germination requirements may, in part, explain shifts in source population representation in the production and restoration sites.

Evolution during seed production for ecological restoration? A molecular analysis of 19 species finds only minor genomic changes

“…Higher gene diversity may provide a higher chance of evolution during cultivation. For example, the contribution of individual source populations to the gene pool of the seed lot can shift during the propagation process (Kucera et al, 2022; St. Clair et al, 2020). The observed stronger differentiation across generations in the material of Producer 1 is thus potentially caused by the more diverse starting material.…”

“…Other studies documented evolutionary changes in ex situ cultivation in botanical gardens (Ensslin & Godefroid, 2019; Rauschkolb et al, 2019), but ex situ populations are usually very small, whereas the cultivation of plants for ecosystem restoration usually involves much larger populations. The few studies that focused specifically on the evolution of plants for ecological restoration worked with individual species and/or documented cultivation only across a single generation (Dyer et al, 2016; Kucera et al, 2022; Pizza et al, 2021; St. Clair et al, 2020). Only one previous study focused on multiple cultivation generations across multiple species, and it found rather minor cultivation effects which differed between species (Nagel et al, 2019).…”

Species‐specific effects of production practices on genetic diversity in plant reintroduction programs

“…While the unintentional loss of genetic diversity through propagation has been a longstanding concern of restoration ecologists (Basey et al., 2015; Espeland et al., 2017; Havens et al., 2004), most studies have documented genetic shifts rather than decreases in genetic diversity (Dyer et al., 2016; Nagel et al., 2019; St. Clair et al., 2020). On the other hand, large scale seed production for restoration has not led to major changes in genetic diversity in other studied species (Kucera et al., 2022; St. Clair et al., 2020), even in those that experience dormancy (Conrady et al., 2022). In some cases, propagation practices can lead to ex situ populations harboring greater levels of genetic diversity compared to in situ populations (Conrady et al., 2022; St. Clair et al., 2020), demonstrating that cultivation, when applied appropriately, can benefit species that are to be restored in harsh in situ conditions (Chivers et al., 2016).…”

“…Clair et al, 2020). On the other hand, large scale seed production for restoration has not led to major changes in genetic diversity in other studied species (Kucera et al, 2022;St. Clair et al, 2020), even in those that experience dormancy (Conrady et al, 2022).…”

Plants cultivated for ecosystem restoration can evolve towards a domestication syndrome

“…The potential evolution of wild plants during cultivation for ecological restoration has been intensely debated, but experimental evidence is scarce and inconclusive (10,11). Some previous studies used molecular markers to understand genetic drift during the seed production (18,19), yet none of these focused on adaptive genetic variation and thus, were unable to test for selection (20). Common garden studies that tested for heritable phenotypic changes were so far limited to individual species, only one cultivated generation, or they lacked adequate comparisons to the wild ancestors (21)(22)(23), and the obtained results vary.…”