Intraspecific and phenotypic variation in salinity responses of invasive Spartina densiflora from Pacific estuaries of North America

Authors: Grewell, Brenda; CASTILLO, JESUS - University Of Sevilla; SKAER THOMASON, MEGHAN - University Of California; DRENOVSKY, REBECCA - John Carroll University

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/19/2014
Publication Date: 12/16/2016
Citation: Grewell, B.J., Castillo, J.M., Skaer Thomason, M.J., Drenovsky, R.E. 2016. Intraspecific and phenotypic variation in salinity responses of invasive Spartina densiflora from Pacific estuaries of North America. In: Ainouche, M. (ed.)Proceedings 4th International Conference on Invasive Spartina, July 7/10, 2014 Universite de Rennes 1, Rennes, France, p. 101-106.

Interpretive Summary: It is important to link functional trait-based responses of invaders to environmental changes to improve our understanding of mechanisms that promote invasiveness. Spartina densiflora (austral cordgrass), native to southern South America, is an aggressive invader of estuarine ecosystems in North America and Europe. The invasion of S. densiflora across a wide latitudinal gradient from California (USA) to British Columbia (Canada) provides a natural model system to study the potential mechanisms underlying the response of invasive populations to substantial variation in climate change, sea level rise and predicted salinity increases in coastal aquatic ecosystems. We collected rhizomes of this invasive weed species from four invasive populations latitudinally distributed along the Pacific Coast from California to Vancouver Island, Canada. We measured functional plant traits associated with growth, and allocation, photosynthesis, leaf pigments, and leaf chemistry and calculated plasticity indices across three imposed salinity treatments in a glasshouse experiment. Our results demonstrate the capacity for S. densiflora plants to adjust to increasing salinity regimes through adjustments in leaf chemistry, leaf pigment, leaf morphology and physiology. The phenotypic plasticity expressed by this plant species contributes to its invasiveness across changing environmental conditions. Understanding potential niche breadth via plasticity or adaptation may help improve assessments of invasion risk and management strategies in this time of rapid climate change.

Technical Abstract: Salinity and tidal inundation induce physiological stress in vascular plant species and influence their distribution and productivity in estuarine wetlands. Plants in these wetlands are subjected to climate change and magnified physiological stresses as these key abiotic processes increase with sea level rise. Understanding the potential of invasive plants to respond to predicted salinity increases improve understanding of their potential niche breadth. To examine potential phenotypic plasticity and mechanisms underlying responses to variation in salinity stress in Spartina densiflora, we collected rhizomes from four invasive populations occurring from California (USA) to Vancouver Island (Canada) on the Pacific Coast of North America. In a common garden experiment, we measured plant traits associated with growth and allocation, photosynthesis, leaf pigments, and leaf chemistry and calculated plasticity indices across imposed salinity treatments. Leaf chemistry, leaf pigments, leaf morphology and physiology all expressed strong plastic responses to salinity, and population was also an important factor for several measured plant traits. Growth and allocation measures were less plastic, with the exception of total leaf area. Salinity-induced changes in leaf chemistry and physiology may compensate to support invasive plant growth with rising estuarine salinity.