Genotype and Elevation Influence Spartina Alterniflora Colonization and Growth in a Created Salt Marsh

Abstract

Colonization, growth, and clonal morphology differ with genotype and are influenced by elevation. Local adaptation of Spartina alterniflora to environmental conditions may lead to dominance by different suites of genotypes in different locations within a marsh. In a constructed marsh, we found reduced colonization in terms of density of clones with increasing distance from edge in a 200‐ha mudflat created in 1996; however, growth in diameter was not different among three 100‐m‐long zones that differed in distance from site edge. Distance from edge was confounded by elevation in this comparison of natural colonization. The rate of clonal expansion in diameter was 3.1 m/yr, and clonal growth was linear over the 28 mo of the study. The area dominated by S. alterniflora in the three distance zones increased concomitantly with clonal growth. However, the lower initial clonal densities and colonization by other plant species resulted in reduced overall dominance by S. alterniflora in the two more‐interior locations. Seedling recruitment was an important component of S. alterniflora colonization at all elevations and distances from edge two years after site creation. Seedlings were spatially very patchy and tended to occur near clones that probably produced them. A field experiment revealed that S. alterniflora height and total stem length varied with genotype, while stem density and flowering stem density did not. Differences between edge and center of clonal patches also occurred for some response variables, and there were also significant interactions with genotype. Differences between edge and center are interpreted as differences in clone morphology. Elevation differences over distances of a few meters influenced total stem length and flowering stem density but not other response variables. Clones that were larger in diameter also tended to have greater stem heights and total stem lengths. A number of plant morphological measures were found to vary significantly among the five genotypes and had broad‐sense heritabilities ranging up to 0.71. These results indicate that S. alterniflora populations developing on new substrata colonize broadly, but growth and reproduction vary with genotype and are influenced by changes in elevation (range: 11.8 cm), and probably other environmental factors, over relatively small distances. Differences in growth and clone morphology of different genets, and the frequent occurrence of seedlings throughout the site, underscore the importance of genetic variability in natural and created populations. Corresponding Editor: J. B. Zedler.

Prediction of velocity profiles and longitudinal dispersion in salt marsh vegetation

“…Finally, vegetation morphology or density may also vary across the horizontal plane over a length-scale L a ϭ O(10-100 m) (Christiansen et al 2000;Proffitt et al 2003). When clouds grow to this scale, the horizontal heterogeneity contributes another mechanism of dispersion similar to the macrodispersion observed in groundwater flow through an array of lenses of varying conductivity (e.g., Cherblanc et al 2003;Russo 2003).…”

Cordgrass Biomass in Salt Marshes

“…Thus, several species of Spartina, such as S. alterniflora or S. maritima, show clearly distinguishable tall and short growth forms (Shea et al, 1975;Mendelssohn, 1979;Anderson & Treshow, 1980;Howes et al, 1986;Pezeshki & DeLaune, 1991;Castillo et al, 2005a). Some studies have concluded that the observed variability in growth forms among Spartina populations may be the result of genetic differentiation (Gallagher et al, 1988;Sanchez et al, 1997;Proffitt et al, 2003), identifying ecotypes with different canopy heights and biomass accumulation (Lessmann et al, 1997;Daehler, 1999;Otero et al, 2000;Seliskar et al, 2002;Proffitt et al, 2005). In contrast, other studies have attributed different growth forms to phenotypic plasticity in response to differences in environmental factors (Anderson & Treshow, 1980), such as the availability of nutrients (Dai & Wiegert, 1997;Wigand et al, 2003;Zhao et al, 2010), salinity (Phelger et al, 1971;Trnka & Zedler, 2000) or sediment anoxia (Castillo et al, 2005a).…”

The emerging role of genetic diversity for ecosystem functioning: Estuarine macrophytes as models

“…The importance of genetic diversity should increase as the genetic differentiation between genotypes grows. Findings of strong genotype differences in the salt marsh plant Spartina alterniflora (Proffitt 2003) make it highly plausible that similar aggregate diversity responses would occur if genotypic diversity had been a treatment factor.…”