• Energy Research

AbstractSpecies can respond to environmental pressures through genetic and epigenetic changes and through phenotypic plasticity, but few studies have evaluated the relationships between genetic differentiation and phenotypic plasticity of plant species along changing environmental conditions throughout wide latitudinal ranges. We studied inter‐ and intrapopulation genetic diversity (using simple sequence repeats and chloroplast DNA sequencing) and inter‐ and intrapopulation phenotypic variability of 33 plant traits (using field and common‐garden measurements) for five populations of the invasive cordgrass Spartina densiflora Brongn. along the Pacific coast of North America from San Francisco Bay to Vancouver Island. Studied populations showed very low genetic diversity, high levels of phenotypic variability when growing in contrasted environments and high intrapopulation phenotypic variability for many plant traits. This intrapopulation phenotypic variability was especially high, irrespective of environmental conditions, for those traits showing also high phenotypic plasticity. Within‐population variation represented 84% of the total genetic variation coinciding with certain individual plants keeping consistent responses for three plant traits (chlorophyll b and carotenoid contents, and dead shoot biomass) in the field and in common‐garden conditions. These populations have most likely undergone genetic bottleneck since their introduction from South America; multiple introductions are unknown but possible as the population from Vancouver Island was the most recent and one of the most genetically diverse. S. densiflora appears as a species that would not be very affected itself by climate change and sea‐level rise as it can disperse, establish, and acclimate to contrasted environments along wide latitudinal ranges.

AbstractSpecies can respond to environmental pressures through genetic and epigenetic changes and through phenotypic plasticity, but few studies have evaluated the relationships between genetic differentiation and phenotypic plasticity of plant species along changing environmental conditions throughout wide latitudinal ranges. We studied inter‐ and intrapopulation genetic diversity (using simple sequence repeats and chloroplast DNA sequencing) and inter‐ and intrapopulation phenotypic variability of 33 plant traits (using field and common‐garden measurements) for five populations of the invasive cordgrass Spartina densiflora Brongn. along the Pacific coast of North America from San Francisco Bay to Vancouver Island. Studied populations showed very low genetic diversity, high levels of phenotypic variability when growing in contrasted environments and high intrapopulation phenotypic variability for many plant traits. This intrapopulation phenotypic variability was especially high, irrespective of environmental conditions, for those traits showing also high phenotypic plasticity. Within‐population variation represented 84% of the total genetic variation coinciding with certain individual plants keeping consistent responses for three plant traits (chlorophyll b and carotenoid contents, and dead shoot biomass) in the field and in common‐garden conditions. These populations have most likely undergone genetic bottleneck since their introduction from South America; multiple introductions are unknown but possible as the population from Vancouver Island was the most recent and one of the most genetically diverse. S. densiflora appears as a species that would not be very affected itself by climate change and sea‐level rise as it can disperse, establish, and acclimate to contrasted environments along wide latitudinal ranges.

AbstractBackground and AimsSea level rise (SLR) associated with climate change is intensifying permanent submersion and salinity in salt marshes. In this scenario, hybridization between native and invasive species may result in hybrids having greater tolerance of abiotic stress factors than their parents. Thus, understanding the responses of native and invasive halophytes and their hybrids to interacting physiological stresses imposed by SLR is key to native species conservation. We analysed how salinity, inundation depth and their interaction impact the functional traits of native and invasive cordgrass species and their hybrid (genus Spartina; Poaceae).MethodsIn a mesocosm experiment, we evaluated interactive stress effects of three inundation depths (4.5, 35.5 and 55 cm) and four aqueous salinities (0.5, 10, 20 and 40 ppt) on 27 functional traits of native Spartina foliosa, invasive S. densiflora and their hybrid S. densiflora × S. foliosa from San Francisco Estuary.Key ResultsThe combined effect of salinity and inundation led to synergistic effects on leaf biochemical stress indicators. Spartina foliosa behaved as a stress-tolerant species, with high leaf sodium exudation rate and glycine betaine concentrations that also increased with stress. Spartina foliosa was less sensitive to salinity than S. densiflora and the hybrid but was highly growth-limited in response to increased inundation and salinity. Spartina densiflora was fast-growing in low-stress conditions and tolerated moderate interactive stresses. The hybrid produced more biomass, rhizome reserves and tillers than its parents, even under the most stressful conditions. Transgressivity improved the hybrid’s capacity to deal with flooding stress more so than its response to increasing salinity.ConclusionsBased on our observations, we predict that established populations of both native and invasive cordgrasses will experience reduced vegetative and sexual fitness in response to SLR. In particular, the combined effects of high salinity and deep inundation may decrease floret production in S. densiflora, a key trait for the spread of its invasive populations. In contrast, the hybrid likely will be able to sustain its invasiveness under SLR based on its ability to maintain growth and biomass production under stressful conditions.

AbstractBackground and AimsSea level rise (SLR) associated with climate change is intensifying permanent submersion and salinity in salt marshes. In this scenario, hybridization between native and invasive species may result in hybrids having greater tolerance of abiotic stress factors than their parents. Thus, understanding the responses of native and invasive halophytes and their hybrids to interacting physiological stresses imposed by SLR is key to native species conservation. We analysed how salinity, inundation depth and their interaction impact the functional traits of native and invasive cordgrass species and their hybrid (genus Spartina; Poaceae).MethodsIn a mesocosm experiment, we evaluated interactive stress effects of three inundation depths (4.5, 35.5 and 55 cm) and four aqueous salinities (0.5, 10, 20 and 40 ppt) on 27 functional traits of native Spartina foliosa, invasive S. densiflora and their hybrid S. densiflora × S. foliosa from San Francisco Estuary.Key ResultsThe combined effect of salinity and inundation led to synergistic effects on leaf biochemical stress indicators. Spartina foliosa behaved as a stress-tolerant species, with high leaf sodium exudation rate and glycine betaine concentrations that also increased with stress. Spartina foliosa was less sensitive to salinity than S. densiflora and the hybrid but was highly growth-limited in response to increased inundation and salinity. Spartina densiflora was fast-growing in low-stress conditions and tolerated moderate interactive stresses. The hybrid produced more biomass, rhizome reserves and tillers than its parents, even under the most stressful conditions. Transgressivity improved the hybrid’s capacity to deal with flooding stress more so than its response to increasing salinity.ConclusionsBased on our observations, we predict that established populations of both native and invasive cordgrasses will experience reduced vegetative and sexual fitness in response to SLR. In particular, the combined effects of high salinity and deep inundation may decrease floret production in S. densiflora, a key trait for the spread of its invasive populations. In contrast, the hybrid likely will be able to sustain its invasiveness under SLR based on its ability to maintain growth and biomass production under stressful conditions.

Restoration of salt marshes is critical in the context of climate change and eutrophication of coastal waters because their vegetation and sediments may act as carbon and nitrogen sinks. Our primary objectives were to quantify carbon (C) and nitrogen (N) stocks and sequestration rates in restored marshes dominated by Spartina maritima to provide support for restoration and management strategies that may offset negative aspects of eutrophication and climate change in estuarine ecosystems. Sediment C content was between ca. 13 mg C g(-1)and sediment N content was ca. 1.8 mg N g(-1). The highest C content for S. maritima was recorded in leaves and stems (ca. 420 mg C g(-1)) and the lowest in roots (361 ± 4 mg C g(-1)). S. maritima also concentrated more N in its leaves (31 ± 1 mg N g(-1)) than in other organs. C stock in the restored marshes was 29.6 t C ha(-1); ca. 16 % was stored in S. maritima tissues. N stock was 3.6 t N ha(-1), with 8.3 % stored in S. maritima. Our results showed that the S. maritima restored marshes, 2.5 years after planting, were sequestering atmospheric C and, therefore, provide some mitigation for global warming. Stands are also capturing nitrogen and reducing eutrophication. The concentrations of C and N contents in sediments, and cordgrass relative cover of 62 %, and low below-ground biomass (BGB) suggest restored marshes can sequester more C and N. S. maritima plantations in low marshes replace bare sediments and invasive populations of exotic Spartina densiflora and increase the C and N sequestration capacity of the marsh by increasing biomass production and accumulation.

Restoration of salt marshes is critical in the context of climate change and eutrophication of coastal waters because their vegetation and sediments may act as carbon and nitrogen sinks. Our primary objectives were to quantify carbon (C) and nitrogen (N) stocks and sequestration rates in restored marshes dominated by Spartina maritima to provide support for restoration and management strategies that may offset negative aspects of eutrophication and climate change in estuarine ecosystems. Sediment C content was between ca. 13 mg C g(-1)and sediment N content was ca. 1.8 mg N g(-1). The highest C content for S. maritima was recorded in leaves and stems (ca. 420 mg C g(-1)) and the lowest in roots (361 ± 4 mg C g(-1)). S. maritima also concentrated more N in its leaves (31 ± 1 mg N g(-1)) than in other organs. C stock in the restored marshes was 29.6 t C ha(-1); ca. 16 % was stored in S. maritima tissues. N stock was 3.6 t N ha(-1), with 8.3 % stored in S. maritima. Our results showed that the S. maritima restored marshes, 2.5 years after planting, were sequestering atmospheric C and, therefore, provide some mitigation for global warming. Stands are also capturing nitrogen and reducing eutrophication. The concentrations of C and N contents in sediments, and cordgrass relative cover of 62 %, and low below-ground biomass (BGB) suggest restored marshes can sequester more C and N. S. maritima plantations in low marshes replace bare sediments and invasive populations of exotic Spartina densiflora and increase the C and N sequestration capacity of the marsh by increasing biomass production and accumulation.