Submitted to: New Phytologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/19/2013
Publication Date: 8/1/2013
Publication URL: http://handle.nal.usda.gov/10113/58767
Citation: Aspinwall, M.J., Lowry, D.B., Taylor, S.H., Juenger, T.E., Hawkes, C.V., Johnson, M.V., Kiniry, J.R., Fay, P.A. 2013. Genotypic variation in traits linked to climate and aboveground productivity in a widespread C4 grass: Evidence for a functional trait syndrome. New Phytologist. 199:966-980. Interpretive Summary: Natural variation in growth and function among plants of a given species is important for understanding how and why plants become adapted to their local environment. In this study, we examined how switchgrass, a native tallgrass prairie species, collected from sites ranging from Nebraska to south Texas, differed in growth and function. We found that switchgrass from cooler sites started growing later in the season, flowered early, used water less efficiently, and were smaller than switchgrass from warmer sites. These results have implications for natural and managed grasslands under predicted changes in climate.
Technical Abstract: Growth and leaf functional trait variation among genotypes of a geographically widespread dominant species could provide insight into mechanisms of local adaptation and may be important for predicting species and ecosystem responses to environmental change. Under common garden conditions, we grew nine genotypes of the dominant C4-tallgrass prairie species Panicum virgatum L. (switchgrass) representing latitudes from Nebraska to south Texas. We hypothesized that genotype productivity, morphology, and leaf functional traits would align with latitude of origin, thus providing evidence for local adaptation. Genotypes from warmer latitudes began growth earlier, flowered later, produced more aboveground biomass, and had greater leaf lamina thickness, leaf mass per area (LMA), intrinsic water-use efficiency (iWUE), efficiency of photosystem II (Phi PSII), and C:N ratios, yet lower leaf nitrogen per unit mass (Nm) and chlorophyll (Chl) compared to genotypes from cooler latitudes. Moreover, genotype leaf thickness showed high broad-sense heritability (0.60) and was genetically correlated with iWUE, Phi PSII, Nm, and Chl. Overall, productivity and leaf functional trait variation among P. virgatum genotypes was largely determined by growing season length. These results provide strong evidence for local adaptation in P. virgatum with broad implications for natural and managed grassland ecosystem function under climate change.