DIFFERENCES IN PHENOTYPIC PLASTICITY AMONG GENOTYPES OF INVASIVE PHRAGMITES AUSTRALIS IN RESPONSE TO ELEVATED CO² AND NITROGEN

Emily Geoghegan

Mentors: Dr. Thomas Mozdzer & Dr. Josh Caplan

Increases in nitrogen and atmospheric carbon dioxide have caused significant changes in the diversity and productivity of tidal wetlands by creating an environment favorable to invasion.  A Eurasian strain of the common reed (Phragmites australis) has aggressively invaded tidal marshes on the North American Atlantic Coast, threatening the interspecific diversity, and therefore stability, of wetland ecosystems.  Recent studies have shown that certain Phragmites genotypes become more frequent under varying levels of carbon dioxide or nitrogen.  While invasive Phragmites is known to outperform the native strain due to greater phenotypic plasticity, it is unknown which invasive genotypes will respond more effectively to near climate change conditions.  We are investigating the effects of factorial treatments of increased nitrogen and carbon dioxide on invasive Phragmites genotypes to determine how intraspecific diversity may be affected by shifting environmental conditions.  In order to do this, we will observe changes in functional traits—such as biomass and specific leaf area—of four invasive Phragmites genotypes placed in one of six CO2 controlled chambers representing ambient and near future (+300ppm CO2) conditions (n=3), with half of the plants being exposed to elevated nitrogen (25g N/m² per year) levels over the course of ten weeks.  We predict that there will be differences in growth and productivity between genotypes when exposed to the same conditions, which could suggest that certain genotypes of Phragmites could become more prevalent in certain environments.  As individuals thrive under these new conditions and produce more seeds, the number of individuals in each genotype could increase.  This would greatly increase the amount of intraspecific diversity among invasive Phragmites populations.