Limits to Local Sourcing in Herbaceous Plant Restoration

The appropriate collection zone for seeds and transplants is a key concern for plant restoration ecology, with local sourcing thought to be the “gold standard.” Local sourcing is based on the premise that most plant species are genetically adapted to the local environment through the action of natural selection, and that non-local ecotypes will disrupt this adaptation. However, a number of factors may allow practitioners to expand sourcing. These include genetic variation that is non-adaptive, phenotypic plasticity, climate change, disturbance, and a host of practical issues. These factors are reflected in the range of collection zone protocols that have been developed by practitioners, ranging from local sourcing to bypassing species identity in favor of function. In addition, phenotypic plasticity, because it allows a single genotype to produce different phenotypes in response to environmental variation, may also allow for a broadened collection zone. Little is known about the degree of genetic variation and local adaptation for most plant species. More evidence-based sourcing could result from collaboration between researchers and practitioners, including tracking seed and plant sources, their performance at restoration sites, and conducting reciprocal transplant studies. Inferring the degree of gene flow based on morphological characters has also shown some promise for inferring genetic variation among populations. Research that includes more robust sampling of populations within species would lead to more precise estimates of gene flow in relation to plant traits.