Phenotypic plasticity of invasive Spartina densiflora (Poaceae) along a broad latitudinal gradient on the Pacific Coast of North America

Abstract

• Premise of the study: Phenotypic acclimation of individual plants and genetic differentiation by natural selection within invasive populations are two potential mechanisms that may confer fitness advantages and allow plants to cope with environmental variation. The invasion of Spartina 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 and other environmental variables. • Methods: We examined morphological and physiological leaf traits of Spartina densiflora plants in populations from invaded estuarine sites across broad latitudinal and climate gradients along the Pacific west coast of North America and in favorable conditions in a common garden experiment. • Key results: Our results show that key foliar traits varied widely among populations. Most foliar traits measured in the field were lower than would be expected under ideal growing conditions. Photosynthetic pigment concentrations at higher latitudes were lower than those observed at lower latitudes. Greater leaf rolling, reduced leaf lengths, and lower chlorophyll and higher carbon concentrations were observed with anoxic sediments. Lower chlorophyll to carotenoids ratios and reduced nitrogen concentrations were correlated with sediment salinity. Our results suggest that the variations of foliar traits recorded in the field are a plastic phenotypic response that was not sustained under common garden conditions. • Conclusions: Spartina densiflora shows wide differences in its foliar traits in response to environmental heterogeneity in salt marshes, which appears to be the result of phenotypic plasticity rather than genetic differentiation.

Low genetic diversity contrasts with high phenotypic variability in heptaploid Spartina densiflora populations invading the Pacific coast of North America

“…See Castillo et al. (, ) for a full description of sampling sites. The southernmost population analyzed was at Corte Madera Creek in San Francisco Bay Estuary (SF; 37°56′33″N, 122°30′55″W; California, USA) in a middle‐elevation salt marsh dominated by S. densiflora , which was intentionally introduced from Humboldt Bay to stabilize tidal creek banks in a wetland restoration project in the late 1970s (Faber, ).…”

“…49°20′N, Canada) provides a natural model system for an integrated study of the potential mechanisms underlying the response of species traits to substantial variation in climate and other environmental variables and an opportunity to investigate how species establish and succeed in novel and contrasted environments. Previous studies in the field and in common‐garden experiments on invasive S. densiflora populations sampled along the Pacific coast of North America revealed high levels of phenotypic plasticity for some foliar and tussock traits (Castillo, Grewell, Pickart, Figueroa, & Sytsma, ; Castillo et al., ; Grewell, Castillo, Skaer‐Thomason, & Drenovsky, ). However, the levels of genetic diversity in these S. densiflora populations along the Pacific coast of North America experiencing high variability in sedimentary and climatic conditions have not been studied.…”

“…Our overall objective was to assess whether trait responses were dependent on genetic differentiation or phenotypic plasticity or a combination of both factors. We hypothesized that (i) S. densiflora would show low genetic diversity and high phenotypic plasticity in response to contrasted environments and that they would be independent from each other, based on previous observations (Castillo et al., , ; Grewell et al., ); (ii) due to the polyploid and hybrid nature of S. densiflora , at least certain foliar traits would show both high plasticity and high intrapopulation variability, as leaf (the organ of photosynthesis and transpiration) is highly sensitive to environmental conditions (Stephenson, Oliver, Burgos, & Gbur, ); and (iii) genetically based and environmental‐based interpopulation differences in response to a changing environment would increase with geographic distance.…”

Physical stress modifies top‐down and bottom‐up forcing on plant growth and reproduction in a coastal ecosystem

“…This species is a perennial salt-tolerant grass native to South America (see Bortolus 2006) that can tolerate a wide range of environmental conditions (Nieva et al 2001), but is usually associated with strong phenotypic changes (Castillo et al 2014). This lagoon is affected by semidiurnal microtides (,1 m) and is characterized by mudflats in the low zone followed by a monoculture of the austral cordgrass Spartina densiflora Brongn.…”

Geographical variation in vegetative growth and sexual reproduction of the invasive Spartina alterniflora in China

“…; Davidson, Jennions & Nicotra ; Castillo et al . ). A better understanding of these two processes would allow us to better understand why some introductions of exotic species fail, others succeed but remain confined to a small geographic area, and others spread to cover wide geographic areas (Richardson & Pyšek ; Colautti, Eckert & Barrett ; Moran & Alexander ).…”