In this blog post Associate Editor Brian Wilsey discusses a paper he recently handled by Kate Gallagher and Stuart Wagenius ‘Seed source impacts germination and early establishment of dominant grasses in prairie restorations’
Growing propagules from wild populations in cultivation could alter their genetics. For example, it has long been known that the selection pressures differ between hatchery-raised salmon and wild salmon (Waples 1991). Similar differences may exist between native plants grown in production fields by seed companies and wild populations. Native seeds produced by seed companies provide a valuable source of seeds for restorations, but are there differences in seed germination and other phenotypic characteristics compared to wild sources? What about differences between seed from restorations vs. remnants? A new paper by Gallagher and Wagenius tested these ideas in a study of three common grasses.
The authors compared seed germination, early survival, and plant height in the common grasses Andropogon gerardii (big bluestem), Bouteloua curtipendula (side-oats grama), and Sorghastrum nutans (Indian grass) across seed provenance types and among sources within types. Provenance types denoted seeds collected from 1) small unplowed remnants, 2) restorations, or 3) seed company propagation fields. Differences in germination and survival during the first two months were found among provenance types for two of the species. In Bouteloua curtipendula, germination and survival were highest in plants from nurseries and restorations, and were lower in plants from remnants. In Andropogon gerardii, germination and survival were highest in plants from nursery seeds, intermediate in plants from restoration seeds, and lowest in seeds from remnants. Plants from nursery seeds were taller in field plots compared to plants from remnant seed sources. The third species gave a more variable response. A possible explanation for these differences is that there are different selection pressures among propagation fields at seed companies, restorations, and in the small isolated remnants sampled. Further research will be necessary to pinpoint the genetic mechanism behind these differences.
The authors followed the plants only over the first growing season, and it will be important to determine if these effects affect restorations over longer time frames (Kettenring et al. 2014). Sometimes early differences can subside with time, and sometimes they can become enhanced (i.e. when priority effects are important). There were also important differences in the response of the three species used. Grasses can be rhizomatous (sod grass) or bunch-grasses, can be tall or short (Wilsey 2010). Grasslands are delineated into short, mixed and tallgrass prairie based on the height of the dominant grasses present. Their results also point out that C4 grasses are not all ecologically equivalent. Overall, the results of Gallagher and Wagenius suggest an additional way that restoration plantings can be different from the remnant areas that we are using as references.
Kettenring, K.M., Mercer, K.L., Reinhardt Adams, C. and J. Hines. 2014. Application of genetic diversity-ecosystem function research to ecological restoration. Journal of Applied Ecology 51:339-348
Waples, W. S. 1991. Genetic interactions between hatchery and wild salmonids: lessons from the Pacific Northwest. Can. ]. Fish. Aquat. Sci. 48 (Suppl. 1): 124-1 33.
Wilsey, B.J. 2010. Productivity and subordinate species response to dominant grass species and seed source during restoration. Restoration Ecology 18:628-637