02048nas a2200157   4500008004100000245011900041210006900160300000900229490000600238520149400244100001801738700001401756700002301770700001901793856007801812       2013                        eng d00aPopulation origin and genome size do not impact Panicum virgatum (switchgrass) responses to variable precipitation0 aPopulation origin and genome size do not impact Panicum virgatum  a37 -0 v43 a<p>Population-level adaptation to broad-scale regional climates or within-population variation in genome size of the genetically and phenotypically diverse C4 grass, Panicum virgatum (switchgrass), may influence the responses of this species to future precipitation variability associated with climate change. Therefore, we investigated P. virgatum responses to water variability between natural populations collected across a latitudinal gradient and among individuals spanning a range of genomes sizes within these populations. P. virgatum plants from natural populations originating from Kansas, Oklahoma, and Texas, U.S.A, received frequent, small precipitation events (&ldquo;ambient&rdquo;) or infrequent, large precipitation events (&ldquo;altered&rdquo;) to simulate contrasting rainfall variability expected for this region. We measured leaf-level physiology, aboveground biomass and genome size for each individual. Gas exchange rates and aboveground biomass varied significantly by population origin but did not differ by genome size. Altered precipitation treatments reduced leaf-level physiological rates; however this result did not vary by population or genome size. Our results suggest that trait variation in P. virgatum is primarily attributed to population-level adaptation across a latitudinal gradient, not genome size, and that neither population-level adaptation nor genome size may be important predictors of P. virgatum responses to future climatic conditions.</p>1 aO’Keefe, K.1 aTomeo, N.1 aNippert, Jesse, B.1 aSpringer, C.J.  uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/ES12-00339.1