Ecophysiological differences between genetic lineages facilitate the invasion of non‐native Phragmites australis in North American Atlantic coast wetlands

Abstract

Summary1. Over the last century, native Phragmites australis lineages have been almost completely replaced along the North American Atlantic coast by an aggressive lineage originating from Eurasia. Understanding the mechanisms that facilitate biological invasions is critical to better understand what makes an invasive species successful. 2. Our objective was to determine what makes the introduced lineage so successful in the study area by specifically investigating if morphological and ecophysiological differences exist between native and introduced genetic lineages of P. australis. We hypothesized a priori that due to phenotypic differences and differences in plant nitrogen (N) content between lineages, the introduced lineage would have a greater photosynthetic potential. 3. In situ ecophysiological and morphological data were collected for 2 years in a mid-Atlantic tidal marsh and in a glasshouse experiment. We measured photosynthetic parameters (A max , water use efficiency, stomatal conductance) using infrared gas analysis, in conjunction with ecophysiological and morphological parameters [specific leaf area (SLA), leaf area, chlorophyll content, N content]. 4. Introduced P. australis maintained 51% greater rates of photosynthesis and up to 100% greater rates of stomatal conductance which are magnified by its 38-83% greater photosynthetic canopy compared to the native type. The introduced lineage also had a significantly greater SLA and N content. Glasshouse-grown plants and naturally occurring populations demonstrated similar trends in ecophysiological characteristics, verifying the heritability of these differences. These ecophysiological differences, when combined with an extended growing season, provide the mechanism to explain the success of introduced P. australis in North America. 5. Our findings suggest the native type is a low-nutrient specialist, with a more efficient photosynthetic mechanisms and lower N demand, whereas the introduced type requires nearly four times more N than the native type to be an effective competitor. 6. Synthesis. Our study is the first to combine field and laboratory data to explain a biological invasion attributed to ecophysiological differences between genetic lineages. Our data corroborates earlier work suggesting anthropogenic modification of wetland environments has provided the state change necessary for the success of introduced P. australis. Finally, our results suggest that genotypic differences within species merit further investigations, especially when related to biological invasions.

Increased Methane Emissions by an Introduced Phragmites australis Lineage under Global Change

“…elevated CO 2 and N) regardless of genotype. Based on this experiment and previous work showing that introduced Phragmites has traits that support relatively high productivity in field settings (Mozdzer and Zieman 2010;Mozdzer and Megonigal 2012;Tulbure et al 2012), we suggest that the spread of introduced Phragmites will increase CH 4 emissions from North American wetlands, and that methane emissions will increase as atmospheric CO 2 concentration continues to rise. These changes in CH 4 emissions will cause radiative forcing unless there is an equivalent increase in carbon sequestration (Poffenbarger et al 2011).…”

“…We previously demonstrated greater growth and productivity in the introduced lineage under ambient field conditions (Mozdzer and Zieman 2010) and under predicted global change conditions (Mozdzer and Megonigal 2012). As a consequence of greater growth in an elevated CO 2 environment, we hypothesized an increase in CH 4 emissions proportional to plant growth.…”

Long-term effects of a Phragmites australis invasion on birds in a Lake Erie coastal marsh

“…Introduced P. australis shoots emerge earlier in the growing season, produce double the total and leaf biomass, and transition faster from buds to root or shoot tissues (League et al, 2006). Compared with the native lineage, introduced P. australis has a 38 -83% larger photosynthetic canopy, higher specific leaf area, and maintains a 51% greater photosynthetic rate (Mozdzer and Zieman, 2010). Patches of introduced P. australis are also denser and taller than the native lineage.…”

Nitrogen Uptake by Native and Invasive Temperate Coastal Macrophytes: Importance of Dissolved Organic Nitrogen

“…Recent studies highlighting differences between the native and introduced types of Phragmites indicate that the shift from the native to the introduced lineage may have important ecosystem consequences. For example, the introduced types has been shown to have greater aboveground biomass (League et al 2006, Saltonstall and Stevenson 2007, Mozdzer and Zieman 2010, greater stem density (League et al 2006, Mozdzer andZieman 2010), greater height (League et al 2006), and greater photosynthetic rates (Mozdzer and Zieman 2010). However, the question still remains as to what makes the introduced Eurasian lineage so successful in invading North American tidal marshes.…”

“…Since pre-industrial times, anthropogenic N inputs have doubled along the North American Atlantic coast (Galloway et al 2004), and at the same time, introduced Phragmites has outcompeted the native type (Saltonstall 2002), and has expanded into historically unoccupied habitats throughout North American wetlands (Chambers et al 1999). Correlative studies have suggested that increased N availability is a factor facilitating the introduced Phragmites invasion (Bertness et al 2002, King et al 2007, and this shift in N availability is necessary for the invasion since the introduced lineage demands approximately four times more N than the native type in mid-Atlantic tidal marshes (Mozdzer and Zieman 2010). This suggests that there is a threshold of N beyond where the introduced Phragmites has an advantage in the field.…”