Plants cultivated for ecosystem restoration can evolve towards a domestication syndrome

Abstract

The UN Decade on Ecosystem Restoration calls for upscaling restoration efforts, but many terrestrial restoration projects are constrained by seed availability. To overcome these constraints, wild plants are increasingly propagated on farms to produce seeds for restoration projects. During on-farm propagation, the plants face non-natural conditions with different selection pressures, and they might evolve adaptations to cultivation that parallel those of agricultural crops, which could be detrimental to restoration efforts. To test this, we compared traits of 19 species grown from wild-collected seeds to those from their farm-propagated offspring of up to four cultivation generations, produced by two European seed growers, in a common garden experiment. We found that some plants rapidly evolved across cultivated generations towards increased size and reproduction, lower within-species variability, and more synchronized flowering. In one species, we found evolution towards less seed shattering. These trait changes are typical signs of the crop domestication syndrome, and our study demonstrates that it can also occur during cultivation of wild plants, within only few cultivated generations. However, there was large variability between cultivation lineages, and the observed effect sizes were generally rather moderate, which suggests that the detected evolutionary changes are unlikely to compromise farm-propagated seeds for ecosystem restoration. To mitigate the potential negative effects of unintended selection, we recommend to limit the maximum number of generations the plants can be cultivated without replenishing the seed stock from new wild collections. Significance StatementGlobally upscaling demands for native seeds for ecosystem restoration can be covered by agricultural seed propagation. Yet, agricultural practice can unintentionally select for specific traits and reduce adaptive variability, which could affect plant performance once sown back to the wild. We show, across 19 wild species, two seed producers and up to four consecutive cultivated generations, that some plants under cultivation evolved higher vigor, reduced adaptive variability, synchronized flowering and in one case, reduced seed shattering. Yet, there were substantial differences among cultivation lineages, with negligible changes in most, and large changes only in a few cases. Substantial unintended evolution in cultivation is thus rather an exception than the rule.