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.
Highlights
Climate models predict that atmospheric warming will alter global air circulation patterns and result in more variable inter-annual and intra-annual precipitation events over the century, in the North American Great Plains (Christensen et al 2007)
The current study examined the influence of population origin and genome size on the performance of P. virgatum individuals, both within and among natural populations, grown under future climatic conditions
P. virgatum physiology varies extensively among ecotypes and geographically separated populations (Stroup et al 2003, Sanderson et al 2006), it is unknown if within-population variation in genome size is a more important driver of population responses to environmental change than population-level adaptations to regional climates
Summary
Climate models predict that atmospheric warming will alter global air circulation patterns and result in more variable inter-annual and intra-annual precipitation events over the century, in the North American Great Plains (Christensen et al 2007). Altered precipitation variability associated with global climate change may have significant consequences for mesic grassland systems within the Great Plains (Knapp et al 2008). A mechanistic understanding of how dominant C4 grasses respond to variable precipitation will help forecast future ecosystem dynamics because these species have high abundance and impact ecosystem structure and function more than subdominant C3 grasses and forbs (McNaughton and Wolf 1970, Callaway et al 2003, Smith and Knapp 2003, Hughes et al 2008). It is important to understand how dominant species such as Panicum virgatum L. (switchgrass) will respond to future environmental changes
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