Genetic Implications of Plant Sourcing Strategies for Salt Marsh Restoration

Ecosystem restoration aims to recreate the ecological structure, processes, and function of a reference native ecosystem. The structure and composition of restored ecosystems often differ from natural ecosystems, at least in part due to human decisions about which ecosystem characteristics and functions to prioritize. We generally lack an understanding of the precise steps in the restoration process that contribute to those differences, but decisions regarding how and where to source biological material are likely to play a role. Here, we use salt marshes as a system to test the potential for sourcing decisions to influence the genetic diversity and composition of two dominant plant species, Spartina alterniflora and S. patens, in restored salt marshes. We show that there is weak but detectable genetic differentiation across local populations that could serve as sources for restoration efforts, though the magnitude of this differentiation varied by analysis and across the two plant species. In addition, the degree of differentiation is generally greater among plant stocks produced from seed from these potential source populations than among the original populations themselves. Most clearly, plants from commercial nursery sources generally have higher genetic diversity and were highly differentiated from both the local populations and seedlings produced from seed from those local populations. These results are consistent with recent studies showing that restored marshes have distinct genetic characteristics from adjacent natural marshes. Given the demonstrated links between plant genetic variation and ecosystem function and resilience, differences in genetic variation resulting from sourcing decisions have the potential to impact the success of restoration efforts and should be an explicit component of restoration practice.