Assessing Local Adaptation in Four Native Grass Species

Abstract

Prairies in the Pacific Northwest have been reduced to less than l% of their presettlement distribution. Prairie restoration typically requires larger quantities of seeds than can be wild-collected on site, thus site managers often contract with fanners to produce seed. However, if selection pressures in fann fields are radically different than that of sites to be restored, then it is possible that the restoration will fail. We experimentally addressed these concerns with four species of grasses that are being used for restoration in a 956-hectare county park in the S. Willamette Valley. We sought to determine whether the distance between the site of seed production and the site of restoration was within a seed transfer zone by using a reciprocal transplant experiment. Seedlings were assessed for growth and mortality over fifteen-weeks from April-August 2013. We asked whether growing location and seed source affected growth and mortality. We found little evidence for local adaptation. However, we found significant growing location effects on growth and mortality between the two sites; on average plants survived better at Mt. Pisgah, but grew larger at Albany. Adult plants already growing at these sites for these species were also evaluated to determine whether growing location had an effect on damage to the adults and their reproductive output. Location did influence the amount of damage experienced by adults of four species. Festuca roemeri had less damage at Mt. Pisgah.