Contrasting trait responses to latitudinal climate variation in two lineages of an invasive grass

Mozdzer, T. J., Caplan, J. S., Hager, R. N., Proffitt, C. E., & Meyerson, L. A. (2016). Contrasting trait responses to latitudinal climate variation in two lineages of an invasive grass. Biological invasions, 18(9), 2649-2660. PDF.

Summary

Some plants will respond to climate change by shifting ranges and altering growth habits.  Mozdzer et al. uses a common garden approach across a wide latitudinal gradient to test how Phragmites australis might respond to warming temperatures.  Specifically, investigators were curious whether different Phragmites lineages (Type I: subspecies berlandieri, or the Gulf Coast lineage vs. Type M: the introduced lineage found throughout the northeastern US) respond differently to warming.  Phragmites rhizomes were collected from multiple sites in each state and planted in three sites along the eastern seaboard (in Rhode Island, Maryland, and Florida). Researchers measured a variety of metrics of plant growth and production (including height, above and below-ground weights, number of flowering stems, stem density, and measures of photosynthesis) to detect differences in responses among lineages and source populations. 

Take home points

  • Type I produced taller shoots with on average higher above-ground, below-ground, and total biomass relative to Type M, whereas Type M had greater stem density and shorter shoots.

  • Type M flowered with greater frequency and number of flowering stems at all sites.  Type I did not produce flowers in the Rhode Island or Maryland locations, suggesting limited capacity for sexual reproduction at northern latitudes.

  • For Type M Phragmites, aboveground biomass was greatest in middle latitudes, suggesting that the current optimum for aboveground growth is the mid-Atlantic region.

  • Type I was more adaptable to new conditions than Type M.

Management implications

  • Subspecies of Phragmites matter for predicting likealy outcomes with climate change.

  • Type I, (the Gulf Coast lineage, Phragmites australis ssp. berlandieri) is limited by colder temperatures and predicted to expand northward as the climate warms. 

  • Populations of Type M Phragmites may exhibit increased propagule pressure in response to warmer climates

Keywords

Shifting Seasons; Range Shifts; Experiment; Invasive Plant; Aquatic Habitat; Phragmites australis; Phragmites