Global Change Conditions May Cause Different Effects Dependent on Phragmites’ Genotypes

Lyntana Brougham

Mentors: Dr Thomas Mozdzer & Dr Josh Caplan

Atmospheric carbon dioxide concentrations are increasing globally and are expected to reach 700 parts per million(ppm) by the end of the century. Simultaneously, anthropogenic activity has already doubled the amount of reactive nitrogen; this level is expected to increase. Both global change factors are known to affect wetland plant communities, and especially the success of the common reed, Phragmites australis. The invasive Eurasian lineage of Phragmites australis is among the most opportunistic (R-selected) plants, suggesting that, as the environment changes and becomes more favorable, more invasive Phragmites will spread along the Atlantic coast.

Prior studies suggest that near future levels of carbon dioxide and/or nitrogen may affect the frequencies of specific Phragmites’ genotypes in the field. To verify this field observation, we will investigate genotype phenotypic plasticity to factorial treatments of carbon dioxide (ambient or +300ppm) and nitrogen (ambient or +25g N m-2y-1) in 6 replicated CO2 chambers. Rhizome fragments were propagated from three genotypes, to be used in this experiment (a fourth genotype is involved, but only looking at elevated CO2 effects).  Two replicate plants from each genotype were placed in each chamber, and half of the plants within each genotype was also fertilized with nitrogen. Several plant traits, such as total biomass, the shoot-to-root ratio, and leaf area, will be analyzed to investigate if various genotypes of Phragmites australis respond to the conditions at different phenotypic extents, allowing for greater reproductive success.

We expect that certain genotypes be more responsive to a single global change factor, either carbon dioxide or nitrogen, but not both. If the results support this hypothesis, they would suggest that certain genotypes are more effective invaders, and that future invasions may be exacerbated with greater intraspecific genetic diversity. The presence of genotypic advantages would suggest that the invasive abilities of Phragmites australis will evolve and increase over time.