The Role of Population-based Diversity on Productivity: Considerations for Restored Spartina alterniflora Salt Marshes

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Dominant plant species, Texas coasts, reestablished habitat, smooth cordgrass, restoration practices
thesis / dissertation description
Plant genetic diversity can augment ecosystem functions in habitats with low plant species diversity. Salt marshes are typically species-depauperate, a condition that is exacerbated when marshes are restored with a single species such as Spartina alterniflora (Poaceae, smooth cordgrass). Often, these transplants are from a single cultivar or donor bed, which can decrease genetic diversity and cause proliferation of maladapted genes and inbreeding depression. Increasing genetic diversity could enhance the ecological and economical potential of restored marshes. Distinct S. alterniflora genotypes and ecotypes can exhibit unique canopy features but the effects of increasing plant genetic diversity have not been tested. The study objective was to determine if increasing S. alterniflora population diversity could augment plant performance in restored salt marshes. I quantified growth and reproduction among transplants from three Texan populations in field and mesocosm experiments. I also compared plant performance in low and high population diversity assemblages in mesocosms across a range of salinities. Overall transplant growth and reproduction patterns among populations or between diversity assemblages did not differ significantly. This lack of differences might indicate that phenotypic plasticity allowed the plants to adjust to the field and mesocosm conditions. However, populations and diversity treatments might perform differently under atypical, natural stresses where the plants do not have the potential for plastic responses. Collecting different S. alterniflora populations has no foreseeable short term benefits towards augmenting productivity. Instead, restoration protocols should ensure collection of native, neighboring plants or multiple, cultivated plants to mimic genetic diversity of local marshes.

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