Population origin and genome size do not impactPanicum virgatum(switchgrass) responses to variable precipitation

Abstract

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 (“ambient”) or infrequent, large precipitation events (“altered”) 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.

Adaptations between Ecotypes and along Environmental Gradients inPanicum virgatum

“…Physiology is well known to change throughout the development of a plant, and thus mistiming in phenology can have consequences for how plants respond physiologically to major environmental stresses, such as drought and freezing temperatures (Araus et al 2002;McKay et al 2003;Fowler and Limin 2004;Bigras and Bertrand 2006;Roux et al 2006;Lovell et al 2013;Savage and Cavender-Bares 2013). Recent studies suggest a possible association of leaf-level physiological traits with latitude of origin in P. virgatum (Hartman et al 2012;Aspinwall et al 2013), but more studies are needed to clarify the strength of these relationships (O'Keefe et al 2013).…”

“…Both ecotype status (upland vs. lowland) and latitude have been established as important sources of variation responsible for adaptation in P. virgatum (Porter 1966;McMillan 1969b;Sanderson et al 1999b;Casler et al 2004Casler et al , 2007Kiniry et al 2013). The effect of ploidy (tetraploid vs. octoploid) on adaptive trait divergence has also been evaluated in many studies but has rarely been found to have a major effect on phenotype or fitness in the field (Nielsen 1947;McMillan and Weiler 1959;Warner et al 1987;Wullschleger et al 1996;O'Keefe et al 2013). Further, ploidy is often confounded with ecotype (Warner et al 1987;Wullschleger et al 1996) or latitude of origin (Nielsen 1947;McMillan and Weiler 1959;O'Keefe et al 2013), making it difficult to determine the effects these three major sources of variation have on adaptation.…”

“…The effect of ploidy (tetraploid vs. octoploid) on adaptive trait divergence has also been evaluated in many studies but has rarely been found to have a major effect on phenotype or fitness in the field (Nielsen 1947;McMillan and Weiler 1959;Warner et al 1987;Wullschleger et al 1996;O'Keefe et al 2013). Further, ploidy is often confounded with ecotype (Warner et al 1987;Wullschleger et al 1996) or latitude of origin (Nielsen 1947;McMillan and Weiler 1959;O'Keefe et al 2013), making it difficult to determine the effects these three major sources of variation have on adaptation. Future studies need to include many more replicates from across all three potential sources of variation to distinguish their relative importance.…”

Effects of precipitation changes on switchgrass photosynthesis, growth, and biomass: A mesocosm experiment

“…Different switchgrass varieties show different leaf photosynthetic rates, ranging from 25.4 to 35.4 μmol CO 2 m -2 s -1 [ 33 ]. Compared to other crop types, the effects of climate change, such as water stresses on switchgrass, have not been well investigated [ 21 , 34 , 35 ]. Some studies compared differences in annual precipitation and temperature and found that inter-annual precipitation influences soil water availability and then the physiology of switchgrass [ 21 , 29 ].…”

“…The soil water stress significantly reduced switchgrass aboveground biomass, establishment rates of stands, and physiological responses [ 36 – 39 ]. But few experimental studies have been conducted to investigate the responses of switchgrass physiology and growth to climate changes [ 21 , 35 , 39 ].…”