Spartina alterniflora genotype influences facilitation and suppression of high marsh species colonizing an early successional salt marsh

Abstract

Summary1 Genetically based phenotypic and ecotypic variation in a dominant plant species can influence ecological functions and patterns of recruitment by other species in plant communities. However, the nature and degree of importance of genotypic differences is poorly understood in most systems. 2 The dominant salt marsh species, Spartina alterniflora , is known to induce facilitative and competitive effects in different plant species, and the outcomes of interactions can be affected by nutrients and flooding stress. Clonal genotypes, which maintained their different plant architecture phenotypes throughout 31 months of a field experiment, underwent considerable genet-specific senescence in their centres over the last 12 months. 3 Different clonal genotypes and different locations (robust edges vs. senescent centres) permitted significantly different levels of light penetration of the canopy (14.8-77.6%), thus establishing spatial heterogeneity for this important environmental factor. 4 S. alterniflora clonal genotype influenced the degree of suppression of the previously dominant Salicornia bigelovii as well as facilitation of recruitment and growth by other plant species. Aster subulatus and Atriplex patula performed better in Spartina clone centres, and experienced reduced growth in Salicornia -dominated areas. 5 Four other high marsh species ( Borrichia frutescens , Aster tenuifolius , Iva frutescens and Limonium carolinianum ) colonized only into Spartina clones but not into the Salicornia -dominated area. 6 These results suggest that differences in clone size, centre senescence, stem density, height, total stem length and biomass in different genotypes of a dominant marsh plant species can influence recruitment and growth of other plant species. The spatial pattern of habitat heterogeneity is, at least in part, dependent on the genotypic diversity, and possibly the genetic diversity, of such foundation species. 7 We hypothesize that as genotypic diversity increases in populations of a dominant plant species like S. alterniflora , the number and diversity of interactions with other species will increase as well.

Cordgrass Biomass in Salt Marshes

“…As we have shown above cordgrass above-ground biomass accumulation depends on clone architecture and shoot morphology. These traits show high intraspecific variation as described for S. alterniflora (Lessmann et al, 1997;Proffitt et al, 2005), S. densiflora (Nieva et al, 2001a;Castillo et al, 2008b), S. maritima (Sanchez et al, 1997;Castellanos et al, 1998;Otero et al, 2000;Castillo et al 2005a;Castillo et al, 2008a,b) and S. patens (Silander & 7 Antonovics, 1979). Intraspecific changes in growth form may be based on phenotypic plasticity or genotypic differences.…”

“…Among cordgrasses with a "guerrilla" growth-form, S. alterniflora in western Atlantic low salt marshes accumulates between 100 and 1100 g DW m -2 . Changes in S. alterniflora biomass between populations are related mainly with its short and tall forms, varying its shoot height between 20 and 140 cm, also with a highly variable shoot density that changes markedly between 100 and 4000 shoot m -2 (Craft et al, 1999(Craft et al, , 2002(Craft et al, , 2003Proffitt et al, 2005;Culbertson et al, 2008;Darby & Turner 2008b;McFarlin et al, 2008;Sala et al, 2008;Tyrrell et al, 2008;Buchsbaum et al, 2009;Gonzalez Trilla et al, 2009;Krull & Craft, 2009;Michel et al, 2009;Holdredge et al, 2010). One year after invading Chinese marshes, S. alterniflora accumulated ca.…”

“…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).…”

“…Thus, Spartina biomass influences on the carbon content of marsh sediments (Tanner et al, 2010), the marsh carbon stock (Wieski et al, 2010), marsh methane emissions (Cheng et al, 2010), salt marsh microbial community (First & Hollibaugh, 2010;Lyons et al, 2010), grazing (Burlakova et al, 2009), sediment dynamic (Neumeier & Ciavola, 2004;Salgueiro & Cacador, 2007;Li & Yang, 2009), etc. Cordgrass biomass affects the emergent of the habitat structure, facilitating succession development by providing a base for habitat development (Castellanos et al, 1994;Figueroa et al, 2003;Proffitt et al, 2005;Castillo et al, 2008b). For example, S. maritima in European low salt marshes, S. alterniflora in western Atlantic low salt marshes and S. foliosa in Californian low salt marshes are important pioneers and ecosystem autogenic engineers (Castellanos et al, 1994;Castillo et al, 2000;Proffitt et al, 2005).…”

Abiotic modulation of Spartina maritima photobiology in different latitudinal populations

“…The Spartina genus is one of the more successful halophytes, being present in a wide range of latitudes across the globe. Some works have already described latitudinal population differentiation of Spartina species (Lessmann et al, 1997;Daehler et al, 1999;Otero et al, 2000;Seliskar et al, 2002;Proffitt et al, 2005;Álvarez et al, 2010). The members of the Spartina genus have C4 photosynthesis using phosphoenolpyruvate carboxylase (PEPC) to concentrate CO 2 at higher amounts than it would be observed in a C3 organism (Hatch, 1992;Álvarez et al, 2010).…”