Brenda J. Grewell

United States Department of Agriculture | USDA · Agricultural Research Service (ARS), Invasive Species and Pollinator Health Research Unit UC Davis, California

Aims Sea level rise and increases in species invasions are impacting estuarine ecosystems, but physiological tolerances of invasive plants are poorly understood. We investigated the responses of invasive Iris pseudacorus to increasing salinity, inundation and their interaction. We hypothesized that I. pseudacorus would show poor tolerance to salini...

Premise: Understanding recruitment processes of invasive species is central to conservation and management strategies. Iris pseudacorus, an emergent macrophyte, has established invasive populations across a broad global range, and reduces biodiversity in wetland ecosystems. Climate change is altering germination cues, yet studies on the invasion o...

Aim: Tidal wetlands are greatly impacted by climate change, and by the invasion of alien plant species that are being exposed to salinity changes and longer inundation periods resulting from sea level rise. To explore the capacity for the invasion of Iris pseudacorus to persist with sea level rise, we initiated an intercontinental study along estua...

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 Columb...

Global environmental change will affect non-native plant invasions, with profound potential impacts on native plant populations, communities and ecosystems. In this context, we review plant functional traits, particularly those that drive invader abundance (invasiveness) and impacts, as well as the integration of these traits across multiple ecolog...

Intraspecific variation in functional traits between native and introduced plant species may underlie resilience and invasiveness of introduced species. We explored if observed phenotypic variation of Iris pseudacorus L. between populations in the native vs. introduced ranges results from genetic differentiation and/or phenotypic plasticity. Seeds...

Intraspecific variation in functional traits between native and alien plant species may underlie resilience and invasiveness of aliens. We explored if observed phenotypic variation of Iris pseudacorus L. between populations in the native vs. introduced ranges results from genetic differentiation and/or phenotypic plasticity. Seeds were collected fr...

The U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS) has been a leader in weed science research covering topics ranging from the development and use of integrated weed management (IWM) tactics to basic mechanistic studies, including biotic resistance of desirable plant communities and herbicide resistance. ARS weed scientists...

Seed burial under wrack, mats of water-transported plant debris, can limit recruitment of seedlings in wetlands. In a greenhouse experiment, we studied the effects of wrack burial (0, 1, 2, 4, 8 cm depths) on germination and emergence of the macrophyte Iris pseudacorus, native to Europe, Mediterranean Basin, and western Asia, that has invaded wetla...

Climate change and biological invasions by plant pests (weeds), agriculture and forest insect pests (insects), and microbial pests (plant pathogens) are complex interactive components of global environmental change. The influence of pest distribution and prevalence across landscapes are challenging the conservation and sustainability of natural res...

Seed banks play an important role in determining the spatial and temporal distribution of halophytes in salt marshes. We tested the ability of native Spartina maritima and invasive S. densiflora spikelets to disperse by flotation on water with different salinity concentrations, and the longevity of spikelet viability relative to environmental condi...

South American invasive plants in the genus Ludwigia (Onagraceae) degrade many riparian and aquatic ecosystems worldwide. Biological control may aid in the management of these exotic weeds, but data on the host specificity of Ludwigia natural enemies is limited. The biology and host range of Sudauleutes bosqi Hustache (Coleoptera: Curculionidae), a...

We conducted an intercontinental biogeographic survey to analyze the effects of an invasive plant species in its native and invaded ranges. Our study system included tidal wetlands colonized by Iris pseudacorus L. (yellow flag iris, Iridaceae) along salinity gradients in two estuaries in its native European (Guadalquivir Estuary) and invaded North...

Efforts to understand why some species become successful invaders and why some habitats are more at risk from invasive species is an important research focus in invasion ecology. With current global climate change, evaluation of the effects of shade and drought on cohabiting native and invasive species from extreme ecosystems is especially importan...

Edited by L Sebastiani Efforts to understand why some species become successful invaders and why some habitats are more at risk from invasive species is an important research focus in invasion ecology. With current global climate change, evaluation of the effects of shade and drought on cohabiting native and invasive species from extreme ecosystems...

Exotic water primroses are aggressive invaders in both aquatic and riparian ecosystems worldwide. Water primrose [Ludwigia hexapetala (Hook. & Arn.) Zardini, Gu & P. H. Raven], floating primrose-willow [Ludwigia peploides (Kunth) P. H. Raven subsp. peploides], floating primrose-willow [Ludwigia peploides (Kunth) P. H. Raven subsp. montevidensis (Sp...

Supplementary material includes statistical analyses (GLM), and data on traits of Iris pseudacorus including biomass production and allocation, leaf morphological traits, leaf chemical traits, leaf gas exchange traits, below ground macronutrient storage, and functional plant trait relationships from a greenhouse experiment investigating salinity an...

Invasive alien plant species impart considerable impacts that contribute to the decline of biodiversity worldwide. The ability of an invasive species to overcome barriers to establish and spread in new environments, and the long-term effects of plant invasions supporting their persistence are keys to invasion success. The capacity of introduced spe...

Exotic water primroses (Ludwigia spp.) are aggressive invaders in aquatic ecosystems worldwide. To date, management of exotic Ludwigia spp. has been limited to physical and chemical control methods. Biological control provides an alternative approach for the management of invasive Ludwigia spp. but little is known regarding the natural enemies of t...

Estuarine ecosystems are threatened by climate change and biological invasions. Among global changes, sea-level rise is broadly impacting tidal wetlands, through increases in salinity and alteration of inundation regimes. Extant freshwater plant species are often presumed to be limited to reaches of estuaries with low salinity and narrow tidal rang...

Flowering rush (Butomus umbellatus) is an invasive aquatic plant in northern USA and southern Canada. To better understand the pattern of invasion in North America and implications for management, we investigated genetic diversity and population structure of the more recent western North American invasion and compared it to the earlier eastern Nort...

Biological invasions are impacting the Bay-Delta ecosystem, and compromise regional tidal wetland restoration goals. Global environmental changes, including sea-level rise and frequent droughts, increase salinity and alter inundation regimes that also impact wetland biota. Establishment of new invasive plant populations will depend on their toleran...

Sexual reproduction can enhance the colonization and spread of invasive plants. We aimed to evaluate ecological factors influencing sexual reproduction and dispersal capacity of exotic Spartina taxa. Density of inflorescences, spikelets per inflorescence, percentage of spikelets with caryopses, and density of caryopses were recorded for North Ameri...

The distribution of genetic diversity in invasive plant populations can have important management implications. Alligator weed ( Alternanthera philoxeroides (Mart.) Griseb.) was introduced into the United States around 1900 and has since spread throughout much of the southern U.S. and California. A successful biological control program was initiate...

See the published article related to this research: https://doi.org/10.1002/ecs2.3486

Closely-related species co-occur within heterogeneous habitats by occupying separate ecological niches as the result of divergent selection that maintains adaptive differentiation. Soil salinity is one of the most important factors influencing vegetation distribution in salt marshes, where germination is a critical stage in the life cycle of many h...

Seed germination and seedling establishment are the stages most sensitive to abiotic stress in the plant life cycle. We analyzed the effects of copper, zinc and nickel on seed germination and early seedling growth of native Spartina maritima and invasive S. densiflora from polluted and non-polluted estuaries. Germination percentages for either spec...

Sexual reproduction, a critical life history process in plants, can be altered by heat stress derived from global warming. Sexual reproduction increases genetic diversity, and the ability of plants to respond to environmental changes and dispersal. The capacity for these responses is especially relevant as plants are exposed to rising environmental...

See the published article related to this research: https://doi.org/10.1002/ecs2.3486

Sea level rise (SLR) imposes increasing salinity and inundation stresses in salt marshes which simultaneously face invasions by exotic plant species. We aimed to improve and apply knowledge on the ecophysiological responses of halophytes to SLR to conservation management of salt marshes. In a mesocosm experiment, we measured and compared phosphoeno...

The host range of the thrips Liothrips ludwigi was investigated using single- and multi-generational no-choice nymphal development and oviposition tests. Development, oviposition, and egg viability were quantified when L. ludwigi were fed three exotic Ludwigia species and seven USA native plant species. Liothrips ludwigi completed development and o...

Worldwide, ecosystems are threatened by global changes, including biological invasions. Invasive species arriving in novel environments experience new climatic conditions that can affect their successful establishment. Determining the response of functional traits and fitness components of invasive populations from contrasting environments can prov...

Hybridization might promote o�spring fitness via a greater tolerance to environmental stressors due to heterosis and higher levels of phenotypic plasticity. Thus, analyzing the phenotypic expression of hybrids provides an opportunity to elucidate further plant responses to environmental stress. In the case of coastal salt marshes, sea level rise su...

Hybridization is a relevant evolutionary mechanism linked to the invasiveness of plant species, but little is known about its effect on enzymatic activities in response to stress. We analyzed the effects of salinity on key mechanistic traits of phosphoenolpyruvate carboxylase (PEPC) enzyme for two hybrid taxa derived from native Spartina maritima (...

Knowledge of factors that influence species colonization and abundance during ecological succession is key for conservation and restoration efforts. The tolerance of species to environmental stresses and interspecific interactions influence stages of ecological succession. Species with high tolerance to stress or high competitive ability, such as i...

Soil seed banks play a critical role in the maintenance of wetland plant communities and contribute to revegetation following disturbances. Analysis of the seed bank can therefore inform restoration planning and management. Emergence from seed banks may vary in response to hydrologic conditions and sediment disturbances. To assess the community-lev...

Background and aims: Sea 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...

Non-native aquatic Ludwigia species from a polyploid complex are among the world’s most problematic invasive plants. These emergent, floating-leaved species respond to disturbance through fragmentation of shoots and/or rhizomes, spreading rapidly by hydrochorous dispersal and posing challenges for invasive plant management. While recruitment of clo...

Soil salinity is a key environmental factor influencing germination and seedling establishment in salt marshes. Global warming and sea level rise are changing estuarine salinity, and may modify the colonization ability of halophytes. We evaluated the effects of increasing salinity on germination and seedling growth of native Spartina maritima and i...

Interspecific hybridization is a major mechanism for generating evolutionary novelty in plants. Halophytic Spartina species are often abundant in coastal salt marshes around the world, and they frequently hybridize. Despite a large body of knowledge on the ecology and evolution of Spartina species, taxonomic resources for distinction of complex tax...

Spartina maritima is the only native cordgrass in Europe and Africa and plays an important role in European salt marshes as a primary colonizer. Many aspects of its reproductive biology are unknown. Viable seed production has been described as potentially very low to non-existent. Our primary objective was to evaluate the seed viability of S. marit...

Alternanthera philoxeroides (common name alligatorweed; basionym Bucholzia philoxeroides Mart., synonyms Achyranthes philoxeroides [Mart.] Standl., Telanthera philoxeroides [Mart.] Moq.) is native to South America, invasive, and a noxious weed. In North America, A. philoxeroides occurs in México and the United States. In the USA, A. philoxeroides h...

Climate change can induce temporary, spatial or behavioral changes in species, so that only some species can adapt to the new climatic conditions. In the case of invasive species, it is expected that they will be promoted in a context of global change, given their high tolerance to environmental factors and phenotypic plasticity. Once in the invade...

Edited by L Sebastiani Efforts to understand why some species become successful invaders and why some habitats are more at risk from invasive species is an important research focus in invasion ecology. With current global climate change, evaluation of the effects of shade and drought on cohabiting native and invasive species from extreme ecosystems...

Interspecific hybridization represents an evolutionary force resulting in novel genotypes. The genomic changes that occur as a result of hybridization affect both genome structure and gene expression and consequently determine hybrid phenotypes and ecology. This study provides new data on the dynamics of hybrid invasions, integrating effects of the...

Interspecific hybridization is an important and common evolutionary mechanism, but field-based evaluations of changes in realized niches and zonation patterns of native and exotic hybrids relative to those of their parental plant species are rare. Would native hybrids forming hybrid zones between their parental species show realized niches similar...

Rivers are vulnerable to biological invasion due to hydrologic connectivity, which facilitates post-entry movement of aquatic plant propagules by water currents. Ecological and watershed factors may influence spatial and temporal dispersal patterns. Field-based data on dispersal could improve risk assessment models and management responses. Ludwigi...

Hybridization is a frequent process that leads to relevant evolutionary consequences, but there is a lack of studies regarding the relationships of the variability of the response of parental plant species to environmental gradients and the responses of their hybrids at a phenotypic level. We designed an experiment in which we exposed two reciproca...

Management of riverine ecosystems often requires mitigation of alien plant invasions. Understanding how environmental variation within watersheds influences distribution and spread of invasive plants is essential for restoration of impacted ecological functions. Ludwigia hexapetala, an emergent macrophyte from South America, has aggressively invade...

Species 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 intrapo...

Aquatic ecosystems are vulnerable to biological invasions, and will also be strongly impacted by climate change, including temperature increase. Understanding the colonization dynamics of aquatic invasive plant species is of high importance for preservation of native biodiversity. Many aquatic invasive plants rely on clonal reproduction to spread,...

Environmental temperature is the primary regulator of germination. Global climatic warming may substantially change seed dormancy and germination responses of wetland and riparian plant species. The potential for increased germination capacity, seed dispersal and geographic range expansion of invasive plant species is a particular concern relevant...

Some introduced species spread rapidly beyond their native range and into novel habitats mediated by a high degree of phenotypic plasticity and/or rapid evolutionary responses. In this context, clonality has been described as a significant factor contributing to invasiveness. We studied the abiotic environment and the responses of different tussock...

Salinity and tidal inundation induce physiological stress in vascular plant species and influence their distribution and productivity in estuarine wetlands. Climate change-induced sea level rise may magnify these abiotic stressors and the physiological stresses they can cause. Understanding the potential of invasive plants to respond to predicted s...

Understanding traits underlying colonization and niche breadth of invasive plants is key to developing sustainable management solutions to curtail invasions at the establishment phase, when efforts are often most effective. The aim of this study was to evaluate how two invasive congeners differing in ploidy respond to high and low resource availabi...

Creeping water primroses and water primrose-willows are among the most aggressive aquatic invasive plant invaders in the world. These aquatic Ludwigia species can impart severe ecological, economic, and human health impacts in aquatic ecosystems and threaten critical ecosystem functions. The authors expect these impacts to increase with greater glo...

Dense infestations of invasive perennial pepperweed (Lepidium latifolium L.) are recognized threats to tidal wetland habitat that undermine ecosystem restoration goals in California's San Francisco Bay-Delta Estuary. Pervasive weed invasions are costly and extremely detrimental to natural areas. Careful management is required to achieve effective w...

Water primroses (Ludwigia spp., Onagraceae) native to South America are among the most aggressive aquatic invasive plant invaders in the world and are recognized as the most invasive aquatic plants in France. Their recent aggressive spread is also impacting freshwater ecosystems in California, Oregon, and the southeastern United States. These invas...

The invasion of Spartina densiflora across a wide latitudinal gradient provides a natural model system to study potential mechanisms influencing invasive plant success in response to changes in climate and resulting physiological stress. Linking functional trait-based responses of invaders to environmental variation can elucidate their potential ni...

Ecological restoration and creation of salt marshes is needed to compensate for their degradation and loss, but little is known about halophytes as plant biotools in restoration projects. The aim of this study was to evaluate Sarcocornia perennis spp. perennis, a common halophyte in European, Southern Africa and South America salt marshes, as a res...

Background/Question/Methods Understanding the drivers of plant invasiveness is critically important to identifying and managing potential invaders. Current theories suggest that polyploidy provides an advantage to the establishment and spread of some invasive plant species. Our objective was to compare growth responses to variation in nutrient av...

ABSTRACT Salinity and tidal inundation regimes induce physiological stress in vascular plant species and influence their distribution and productivity in estuarine wetlands. These physico-chemical drivers are expected to increase in intensity with sea level rise. Phenotypic plasticity of ecologically important plant traits may promote invasiveness...

Shifting mosaics of vegetation are a defining feature of Suisun Marsh wetlands. Seasonal changes of plant communities are familiar, but less obvious are changes to vegetation structure and composition that have varied over millennia. In this chapter, we describe contemporary plant communities by the hydrogeomorphic settings that link flora to physi...

Suisun Marsh is the largest tidal wetland in California and a major component of the San Francisco Estuary. It is a refuge for native plants and animals and is major area of “open space” in an increasingly urban region. Suisun Marsh has a long history of being managed for its wildlife, beginning with the native peoples. It persists as a wetland tod...