Evolution during seed production for ecological restoration? A molecular analysis of 19 species finds only minor genomic changes.
A growing number of restoration projects require large amounts of seeds. As harvesting natural populations cannot cover the demand, wild plants are often propagated in large-scale monocultures. There are concerns that this cultivation process may cause genetic drift and unintended selection, altering the genetic properties of the cultivated populations and reducing their genetic diversity. Such changes could reduce the pre-existing adaptation of restored populations and limit their adaptability to environmental change. We used single nucleotide polymorphism (SNP) markers and a pool-sequencing approach to test for genetic differentiation and changes in gene diversity during cultivation in 19 wild grassland species, comparing source populations and up to four consecutive cultivation generations. We linked the magnitudes of genetic changes to the species' breeding systems and seed dormancy to understand the roles of these traits in genetic change. Cultivation changed the genetic composition across cultivated generations only moderately. The genetic differentiation resulting from cultivation was much lower than the natural genetic differentiation between different source regions. The propagated generations harboured even higher gene diversity than wild-collected seeds. Genetic change was stronger in self-compatible than self-incompatible species, probably due to increased outcrossing in monocultures. Synthesis and applications. Our study suggests that large-scale seed production maintains the genetic integrity of natural populations. Increased genetic diversity may even indicate increased adaptive potential of propagated seeds, which would make them especially suitable for ecological restoration. Yet, it remains to be tested whether these molecular patterns will be mirrored also by plant phenotypes. Further, we used seeds from Germany and Austria, where the seed production is regulated and certified, and we do not know yet whether other seed production systems perform equally well.