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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.

Johnson LC, Olsen JT, Tetreault H, DeLaCruz A, Bryant J, Morgan TJ, Knapp M, Bello NM, Baer SG, Maricle BR - Evol Appl (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Biology, Kansas State University Manhattan, KS, USA.

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.

No MeSH data available.


SPAD values (least squares mean estimates ± SE) for each planting site as a function of proportion of growing season elapsed. Higher numbers reflect higher chlorophyll content. A, B letters indicate significant differences among sites at a given GDD. Diamond = Carbondale, circle = Colby, square = Hays, triangle = Manhattan.
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fig06: SPAD values (least squares mean estimates ± SE) for each planting site as a function of proportion of growing season elapsed. Higher numbers reflect higher chlorophyll content. A, B letters indicate significant differences among sites at a given GDD. Diamond = Carbondale, circle = Colby, square = Hays, triangle = Manhattan.

Mentions: There was no evidence for any three-way interaction between planting site, ecotype, and GDD. However, a two-way interaction was apparent between planting site and the quadratic term for proportion GDD on the SPAD chlorophyll absorbance (P < 0.001, Fig.6, Table S2). This is indicative of a site-specific quadratic change in SPAD values over the growing season that was applicable to all ecotypes. Pairwise comparisons between sites (Fig.6) indicate that later in the season (i.e. GDD ≥ 0.6), SPAD index was maximum in Carbondale and minimum at the Manhattan and Hays sites, the latter of which were not significantly different from each other. For GDD ≥ 0.6, the Colby site showed SPAD values intermediate, yet significantly different from the remaining sites. Earlier in the growing season (i.e. GDD < 0.6), the Manhattan planting site showed lower SPAD values relative to the other planting sites, which were not significantly different from each other. Overall, each site showed a quadratic decline in SPAD values as the growing season progressed, except for Carbondale, where SPAD remained high throughout the season (Fig.6).


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.

Johnson LC, Olsen JT, Tetreault H, DeLaCruz A, Bryant J, Morgan TJ, Knapp M, Bello NM, Baer SG, Maricle BR - Evol Appl (2015)

SPAD values (least squares mean estimates ± SE) for each planting site as a function of proportion of growing season elapsed. Higher numbers reflect higher chlorophyll content. A, B letters indicate significant differences among sites at a given GDD. Diamond = Carbondale, circle = Colby, square = Hays, triangle = Manhattan.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4516422&req=5

fig06: SPAD values (least squares mean estimates ± SE) for each planting site as a function of proportion of growing season elapsed. Higher numbers reflect higher chlorophyll content. A, B letters indicate significant differences among sites at a given GDD. Diamond = Carbondale, circle = Colby, square = Hays, triangle = Manhattan.
Mentions: There was no evidence for any three-way interaction between planting site, ecotype, and GDD. However, a two-way interaction was apparent between planting site and the quadratic term for proportion GDD on the SPAD chlorophyll absorbance (P < 0.001, Fig.6, Table S2). This is indicative of a site-specific quadratic change in SPAD values over the growing season that was applicable to all ecotypes. Pairwise comparisons between sites (Fig.6) indicate that later in the season (i.e. GDD ≥ 0.6), SPAD index was maximum in Carbondale and minimum at the Manhattan and Hays sites, the latter of which were not significantly different from each other. For GDD ≥ 0.6, the Colby site showed SPAD values intermediate, yet significantly different from the remaining sites. Earlier in the growing season (i.e. GDD < 0.6), the Manhattan planting site showed lower SPAD values relative to the other planting sites, which were not significantly different from each other. Overall, each site showed a quadratic decline in SPAD values as the growing season progressed, except for Carbondale, where SPAD remained high throughout the season (Fig.6).

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Biology, Kansas State University Manhattan, KS, USA.

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.

No MeSH data available.