Intraspecific variation of a dominant grass and local adaptation in reciprocal garden communities along a US Great Plains' precipitation gradient: implications for grassland restoration with climate change

Abstract

Identifying suitable genetic stock for restoration often employs a ‘best guess’ approach. Without adaptive variation studies, restoration may be misguided. We test the extent to which climate in central US grasslands exerts selection pressure on a foundation grass big bluestem (Andropogon gerardii), widely used in restorations, and resulting in local adaptation. We seeded three regional ecotypes of A. gerardii in reciprocal transplant garden communities across 1150 km precipitation gradient. We measured ecological responses over several timescales (instantaneous gas exchange, medium-term chlorophyll absorbance, and long-term responses of establishment and cover) in response to climate and biotic factors and tested if ecotypes could expand range. The ecotype from the driest region exhibited greatest cover under low rainfall, suggesting local adaptation under abiotic stress. Unexpectedly, no evidence for cover differences between ecotypes exists at mesic sites where establishment and cover of all ecotypes were low, perhaps due to strong biotic pressures. Expression of adaptive differences is strongly environment specific. Given observed adaptive variation, the most conservative restoration strategy would be to plant the local ecotype, especially in drier locations. With superior performance of the most xeric ecotype under dry conditions and predicted drought, this ecotype may migrate eastward, naturally or with assistance in restorations.

Soil Quality and Region Influence Performance and Ranking of Switchgrass Genotypes

“…Grasses with the C 4 photosynthetic pathway tend to be fairly drought tolerant as a rule and this trait likely explains their dominance at the western edge of this cross-continental precipitation gradient (Lane et al, 1998;Knapp et al, 2001). Similar to observations from this study, big bluestem has demonstrated subtle genotypic differences in adaptive responses to a precipitation gradient that ranges from 470 to 1100 mm (Rouse et al, 2011;Johnson et al, 2015). Similar to observations from this study, big bluestem has demonstrated subtle genotypic differences in adaptive responses to a precipitation gradient that ranges from 470 to 1100 mm (Rouse et al, 2011;Johnson et al, 2015).…”

“…As mean annual precipitation increases, drought sensitivity of grasses that have evolved under those conditions also increases (Knapp et al, 2015). Genotypes from dryland environments have greater survivorship under dryland conditions and less diversity in functional disease resistance gene homologs, presumably because there is reduced disease pressure under dryland conditions (Rouse et al, 2011;Johnson et al, 2015). Genotypes from dryland environments have greater survivorship under dryland conditions and less diversity in functional disease resistance gene homologs, presumably because there is reduced disease pressure under dryland conditions (Rouse et al, 2011;Johnson et al, 2015).…”

Phenotypic distribution models corroborate species distribution models: A shift in the role and prevalence of a dominant prairie grass in response to climate change

“…Measurements were averaged across ~23 individuals per population prior to use in the PDMs (Table S3). To determine how well phenotypes of plants grown in the greenhouse reflected responses of plants grown in the field despite common conditions experienced by plants in the greenhouse, we calculated the correlation between the heights of field‐grown plants (13 sites from Johnson et al., ) with mean annual precipitation at those sites.…”

“…Consistent with these observations, A. gerardii increases in stature and productivity with increasing precipitation (Epstein et al., ; Johnson et al., ; McMillan, ; Olsen, Caudle, Johnson, Baer & Maricle, ). Tellingly, a reciprocal common garden experiment established across a ~1200 km transect from western Kansas to Illinois demonstrated local adaptation and strong genetic control over growth‐related traits in this species (e.g., biomass, height; Johnson et al., ; Mendola et al., ). The strong correlation between growth and climatic gradients (Gray et al., ; McMillan, ) suggests that adaptive, genetically controlled phenotypic differences could play an important role in predicting the distribution of A. gerardii in response to climate change.…”

Big bluestem as a bioenergy crop: A review

“…The westernmost ecotype exhibited drought-adapted features with dwarfed stature and significantly reduced canopy area, thus reducing transpiration water loss. The group's data demonstrated strong planting site and ecotype effects as well as interaction between ecotype and planting site [47]. Delucia et al studied the effects of soil temperature on big bluestem growth.…”