PREMISE:Hydrological regime influences wetland plant species distribution and performance. Global warming and extreme weather events are magnifying flooding patterns, and understanding how invasive taxa respond across life stages (establishment vs. established phase) is important for predicting and managing their colonization and spread. Our objective was to measure flood trait responses at contrasting life stages in closely related congeners (Ludwigia peploides, diploid; L. hexapetala, decaploid; Onagraceae) differing in their invasiveness in the field. METHODS:In the field, we assessed phenological responses to seasonal hydrological changes, and in mesocosms, we assessed flood stress responses of establishing shoot fragments under deep-flooded, shallow-flooded, and gradual drawdown hydrological treatments. RESULTS:Counter to expectations, establishing L. peploides expressed more flood tolerance traits in mesocosms than L. hexapetala. For example, L. peploides had greater total leaf area and aerenchyma production than L. hexapetala, supporting its growth under flooding, whereas L. hexapetala expressed more flood escape traits (higher shoot elongation rates, trend for longer shoot internode length). Although L. hexapetala expressed some traits associated with drought tolerance, these trends were not significant. In the field, longer-established plants had a reversed pattern for flood escape versus tolerance traits. Ludwigia peploides rapidly shifted to sexual reproduction as soils began to dry, whereas L. hexaetala flowered regardless of soil moisture availability. CONCLUSIONS:These contrasting patterns of flood tolerance versus escape traits demonstrate that invasive Ludwigia congeners have differing strategies to counter physiological stress induced by flooding and emphasize the importance of life stage in response to environmental variation.

Biological soil crust communities (biocrusts) establishing on gypsum soils have been well-documented for their prolific appearance and rich diversity of lichens and bryophytes. However, studies characterizing gypsum biocrusts have occurred primarily outside of the U.S., most of which lack comparisons to other soil types. We conducted intensive field surveys to evaluate the ground cover and frequency of biocrust functional groups and moss species on gypsum and non-gypsum soils in the U.S. regions with the most extensive gypsum outcrops, the northern Chihuahuan and eastern Mojave Deserts. Study sites were stratified by geomorphology and paired, so that every gypsum site was matched with a non-gypsum site in the same region. We employed canonical correspondence analysis (CCA) to relate the observed differences in biocrust abundance and composition across soil types to distinct environmental variables. Additionally, we assessed species richness of biocrust mosses on gypsum versus non-gypsum soils, as well as in the Chihuahuan versus Mojave Deserts. Our results indicate that differences in biocrust communities on gypsum and non-gypsum soils are predominantly due to gypsum’s profuse dark algal (mostly cyanobacteria-formed) rather than lichen and moss biocrusts in these two hot desert biomes. Biocrust functional groups did not exhibit distinct associations with environmental variables. However, moss species appear to be strongly influenced by environmental variables and exhibited differential preferences for substrate parent material. Moss species richness was greater on gypsum soils and, surprisingly, in the hottest and driest North American Desert, the Mojave. Differences in species richness across deserts were strongly correlated to mean annual and seasonal temperatures, as well as mean winter precipitation. Overall, our data suggest that environmental and climate conditions all play important roles in the ecology of biocrusts, specifically moss diversity and distribution, in the northern Chihuahuan and eastern Mojave Deserts of the U.S. More importantly, we emphasize that gypsum soils of the U.S. are unique refugia for moss-forming biocrusts.

Sea level rise is having major impacts on estuaries due to salinity intrusion. These changes in stress profiles have ripple effects in ecosystems, including altering the invasibility of these wetlands depending on the salt tolerance of the invading species. Alternanthera philoxeroides Mart. (Griseb.) (alligator weed), native to South America and long recognized as one of the world’s worst freshwater aquatic weeds, recently invaded tidal wetlands in California’s San Francisco Bay–Delta Estuary. Generally considered a freshwater-limited glycophyte, observations suggested this invasive macrophyte may have some degree of salinity tolerance, though its degree of tolerance and capacity to spread with increased salinity intrusion were unknown. In two full-factorial greenhouse experiments, we assessed responses of emergent (soil-rooted) and free-floating growth forms of A. philoxeroides to four salinity concentrations (freshwater to euhaline) at the whole-plant (growth, biomass production and allocation, fitness), physiological, and biochemical levels. We also conducted a third experiment exploring the recovery potential of free-floating A. philoxeroides in freshwater following extended exposure to mesohaline to euhaline aqueous salinity. Although sensitivity of A. philoxeroides to increasing salinity was documented, the survival of both growth forms in the full range of salinity treatments was notable and unexpected. Our results indicate A. philoxeroides is a facultative halophyte well adapted to oligohaline–mesohaline salinity levels. Results also revealed the invasive weed’s multiple strategies to survive salinity-induced physiological stress, supporting its survival even at elevated polyhaline to euhaline conditions. The macrophyte expressed functional trait responses spanning stress tolerance, avoidance, and escape strategies that may sustain its spread as estuarine salinity intrusion increases with sea level rise.

Background and Aims Soil endemics have long fascinated botanists owing to the insights they can provide about plant ecology and evolution. Often, these species have unique foliar nutrient composition patterns that reflect potential physiological adaptations to these harsh soil types. However, understanding global nutritional patterns to unique soil types can be complicated by the influence of recent and ancient evolutionary events. Our goal was to understand whether plant specialization to unique soils is a stronger determinant of nutrient composition of plants than climate or evolutionary constraints.Methods We worked on gypsum soils. We analysed whole-plant nutrient composition (leaves, stems, coarse roots and fine roots) of 36 native species of gypsophilous lineages from the Chihuahuan Desert (North America) and the Iberian Peninsula (Europe) regions, including widely distributed gypsum endemics, as specialists, and narrowly distributed endemics and non-endemics, as non-specialists. We evaluated the impact of evolutionary events and soil composition on the whole-plant composition, comparing the three categories of gypsum plants.Key Results Our findings reveal nutritional convergence of widely distributed gypsum endemics. These taxa displayed higher foliar sulphur and higher whole-plant magnesium than their non-endemic relatives, irrespective of geographical location or phylogenetic history. Sulphur and magnesium concentrations were mainly explained by non-phylogenetic variation among species related to gypsum specialization. Other nutrient concentrations were determined by more ancient evolutionary events. For example, Caryophyllales usually displayed high foliar calcium, whereas Poaceae did not. In contrast, plant concentrations of phosphorus were mainly explained by species-specific physiology not related to gypsum specialization or evolutionary constraints.Conclusions Plant specialization to a unique soil can strongly influence plant nutritional strategies, as we described for gypsophilous lineages. Taking a whole-plant perspective (all organs) within a phylogenetic framework has enabled us to gain a better understanding of plant adaptation to unique soils when studying taxa from distinct regions.

Fungi and bacteria are the two dominant groups of soil microbial communities worldwide. By controlling the turnover of soil organic matter, these organisms directly regulate the cycling of carbon between the soil and the atmosphere. Fundamental differences in the physiology and life history of bacteria and fungi suggest that variation in the biogeography of relative abundance of soil fungi versus bacteria could drive striking differences in carbon decomposition and soil organic matter formation between different biomes. However, a lack of global and predictive information on the distribution of these organisms in terrestrial ecosystems has prevented the inclusion of relative abundance of soil fungi versus bacteria and the associated processes in global biogeochemical models. Here, we used a global-scale dataset of > 3000 distinct observations of abundance of soil fungi versus bacteria in the surface topsoil (up to 15 cm) to generate the first quantitative and high-spatialresolution (1 km(2)) explicit map of soil fungal proportion, defined as fungi/fungi + bacteria, across terrestrial ecosystems. We reveal striking latitudinal trends where fungal dominance increases in cold and high-latitude environments with large soil carbon stocks. There was a strong nonlinear response of fungal dominance to the environmental gradient, i.e., mean annual temperature (MAT) and net primary productivity (NPP). Fungi dominated in regions with low MAT and NPP and bacteria dominated in regions with high MAT and NPP, thus representing slow vs. fast soil energy channels, respectively, a concept with a long history in soil ecology. These high-resolution models provide the first steps towards representing the major soil microbial groups and their functional differences in global biogeochemical models to improve predictions of soil organic matter turnover under current and future climate scenarios. Raw datasets and global maps generated in this study are available at https://doi.org/10.6084/m9.figshare.19556419 (Yu, 2022).

The biogeography of relative abundance of soil fungi

Extreme soils often have mineral nutrient imbalances compared to plant nutritional requirements and co-occur in open areas where grazers thrive. Thus, plants must respond to both constraints, which can affect nutrient concentrations in all plant organs. Gypsum soil provides an excellent model system to study adaptations to extreme soils under current grazing practices as it harbours two groups of plant species that differ in their tolerance to gypsum soils and foliar composition. However, nutrient concentrations in organs other than leaves, and their individual responses to simulated herbivory, are still unknown in gypsum plants. We studied plant biomass, root mass ratio and nutrient partitioning among different organs (leaves, stems, coarse roots, fine roots) in five gypsum endemics and five generalists cultivated in gypsum and calcareous soils and subjected to different levels of simulated browsing. Gypsum endemics tended to have higher elemental concentration in leaves, stems and coarse roots than generalist species in both soil types, whereas both groups tended to show similar high concentrations in fine roots. This behaviour was especially clear with sulphur (S), which is found in excess in gypsum soils, and which endemics accumulated in leaves as sulphate (>50% of S). Moreover, plants subjected to clipping, regardless of their affinity to gypsum, were unable to compensate for biomass losses and showed similar elemental composition to unclipped plants. The accumulation of excess mineral nutrients by endemic species in aboveground organs may be a constitutive nutritional strategy in extreme soils and is potentially playing an anti-herbivore role in grazed gypsum outcrops.

Gypsum-exclusive species (gypsophiles), are restricted to gypseous soils in natural environments. However, it is unclear why gypsophiles display greater affinity to gyspeous soils than other soils. These plants are edaphic endemics, growing in alkaline soils with high Ca and S. Gypsophiles tend to show higher foliar Ca and S, lower K and, sometimes, higher Mg than non-exclusive gypsum species, named gypsovags. Our aim was to test if the unique leaf elemental signature of gypsophiles could be the result of special nutritional requirements linked to their specificity to gypseous soils. These nutritional requirements could hamper the completion of their life cycle and growth in other soil types. To test this hypothesis, we cultivated five gypsophiles and five gypsovags dominant in Spanish gypsum outcrops on gypseous and calcareous (non-gypseous) field soil for 29 months. We regularly measured growth and phenology, and differences in leaf traits, final biomass, individual seed mass, seed viability, photosynthetic assimilation and leaf elemental composition. We found all the gypsophiles studied were able to complete their life cycle in non-gypseous soil, producing viable seeds, attaining greater biomass and displaying higher photosynthetic assimilation rates than in gypseous soil. The leaf elemental composition of some species (both gypsophiles and gypsovags) shifted depending on soil, although none of them showed leaf deficiency symptoms. Regardless of soil type, gypsophiles had higher leaf S, Mg, Fe, Al, Na, Mn, Cr and lower K than gypsovags. Consequently, gypsophiles have a unique leaf chemical signature compared to gypsovags of the same family, particularly due to their high leaf S regardless of soil conditions. However, these nutrient requirements are not sufficient to explain why gypsophiles are restricted to gypsum soil in natural conditions.

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 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). METHODS:In 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 RESULTS:The 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. CONCLUSIONS:Based 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.

Premise 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 provide a useful framework to assess species responses to climate change and the variability of these responses among source populations. Much research on macrophytes has focused on establishment from clonal fragments; however, colonization from sexual propagules has rarely been studied. Our objective was to compare trait responses of plants generated from sexual propagules sourced from three climatic regions but grown under common environmental conditions, using L. peploides subsp. montevidensis as a model taxon. Methods We grew seedlings to reproductive stage in experimental mesocosms under a mediterranean California (MCA) climate from seeds collected in oceanic France (OFR), mediterranean France (MFR), and MCA. Results Seed source region was a major factor influencing differences among invasive plants recruiting from sexual propagules of L. peploides subsp. montevidensis. Trait responses of young individual recruits from MCA and OFR, sourced from geographically distant and climatically distinct source regions, were the most different. The MCA individuals accumulated more biomass, flowered earlier, and had higher leaf N concentrations than the OFR plants. Those from MFR had intermediate profiles. Conclusions By showing that the closer a seedling is from its parental climate, the better it performs, this study provides new insights to the understanding of colonization of invasive plant species and informs its management under novel and changing environmental conditions.

Aim Leaf nutrient resorption is a key nutrient conservation trait, which also influences nutrient cycling rates and pools. Most global biogeochemical models assume that resorption is non‐varying at a temporal scale. However, this trait can differ substantially within populations among years. We assessed the commonality of attaining proficient resorption, the factors associated with proficient resorption, as well as the variability of this trait and the factors controlling trait variability. Location Global. Time period 1965–2009. Major taxa studied Plants. Methods We compiled multi‐year nutrient resorption data from the literature, representing 50 studies, 94 unique study locations, and 141 species from 53 families and 29 orders. We used multiple linear regression to relate resorption data, as well as the variability in this trait, expressed as the coefficient of variation, to environmental factors. Results Resource availability was a key driver of resorption, with nutrient‐poor soils associated with more complete resorption and lower resorption plasticity. Nitrogen and phosphorus resorption differentially responded to some drivers, such as leaf habit, soil order and mycorrhizal status. Main conclusions Overall, environmental and biological factors representing a strong selective force for nutrient conservation, such as nutrient‐poor soil orders, semi‐arid soil moisture regimes, or lack of plant mutualists, were associated with complete resorption, whereas incomplete resorption was associated with weak selective forces, such as nutrient‐rich soil orders, or factors impeding this physiological process (e.g., drought). Inter‐annual variability in resorption was common, particularly for phosphorus. This plasticity has implications for ecosystem nutrient cycling and plant productivity, and accounting for this plasticity in dynamic models of nutrient cycling will improve predictions of nutrient limitations and productivity under future climate conditions.

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 clonal aquatic plant species from shoot fragmentation is well documented, regeneration from rhizome bud banks, although common, often is overlooked. It is further unclear how interactions among ploidy and resource availability influence regeneration success of rhizome fragments. We conducted a full factorial experiment in aquatic mesocosms to compare trait responses of Ludwigia congeners differing in ploidy (diploid, decaploid) grown from clonal rhizome fragments under contrasting soil nutrient availability (low, high). Similar to previous work with shoot fragments, the diploid congener had a higher relative growth rate and produced more biomass than the decaploid during this establishment stage of growth. High growth rates and biomass production were associated with greater rhizome N and P and reduced investment in belowground structures. Comparing these results to previous shoot fragment studies with Ludwigia, rhizome fragments appear to have much greater growth potential, suggesting that management strategies should minimize disturbance to prevent fragmentation and dispersal of belowground structures. Furthermore, rapid response to newly colonizing diploid invaders will be essential to minimizing spread, and reductions in nutrient loads to aquatic environments may be more effective toward controlling establishment of the diploid congener than the decaploid.

Hybridization might promote offspring 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 subjects hybrids, and their parents, to longer tidal submergence and higher salinity. We analyzed the phenotypic expression patterns in the hybrid Spartina densiflora x foliosa relative to its parental species, native S. foliosa, and invasive S. densiflora, from the San Francisco Estuary when exposed to contrasting salinities and inundations in a mesocosm experiment. 37% of the recorded traits displayed no variability among parents and hybrids, 3% showed an additive inheritance, 37% showed mid-parent heterosis, 18% showed best-parent heterosis, and 5% presented worst-parent heterosis. Transgressivity, rather than phenotypic plasticity, in key functional traits of the hybrid, such as tiller height, conveyed greater stress tolerance to the hybrid when compared to the tolerance of its parents. As parental trait variability increased, phenotypic transgressivity of the hybrid increased and it was more important in response to inundation than salinity. Increases in salinity and inundation associated with sea level rise will amplify the superiority of the hybrid over its parental species. These results provide evidence of transgressive traits as an underlying source of adaptive variation that can facilitate plant invasions. The adaptive evolutionary process of hybridization is thought to support an increased invasiveness of plant species and their rapid evolution.

Worldwide drylands are threatened by changes in resource availability associated with global environmental change. Functional traits may help predict which species will be most responsive to these alterations in nutrient and water availability. Current functional trait work focuses on tissue construction and nutrient concentrations, but plant performance in low resource environments also may be strongly influenced by traits related to nutrient budgets and allocation. Our overall objective was to compare trait responses in a suite of serpentine and nonserpentine congener pairs from the California chaparral, a biodiverse region facing nutrient deposition and future changes in precipitation. In a common garden greenhouse environment, we grew small plants of Arctostaphylos manzanita, A. viscida, Ceanothus cuneatus, C. jepsonii, Quercus berberidifolia, and Q. durata in contrasting soil nutrient and moisture treatments. We measured a suite of traits representing physiological, growth, and mineral nutrient responses to these treatments. Overall, plant growth rate and leaf-level phosphorus use efficiency were greatest in the low water, high nutrient treatment, and lowest in the high water, low nutrient treatment. Variation in growth rate and plasticity among species and treatments was primarily associated with differences in mineral nutrition-based traits as opposed to differences in biomass allocation or specific leaf area. Namely, faster growing species and species with greater plasticity allocated more nitrogen and phosphorous to leaves and demonstrated greater photosynthetic phosphorus use efficiency. Overall, nonserpentine species had greater plasticity and biomass response to resource addition than serpentine species, and congener pairs responded to these resource additions more similarly to each other than species across congener pairs. This study extends our general understanding of how functional traits may influence species responses to environmental change and highlights the need to integrate mineral nutrition-based traits, including allocation of nutrient pools and nutrient use efficiency into this larger trait framework. Ultimately, this insight can help identify, in part, why coexisting species may vary in sensitivity to anthropogenic driven changes in soil resource availability.

PREMISE OF THE STUDY:Gypsum endemism in plants (gypsophily) is common on gypsum outcrops worldwide, but little is known about the functional ecology of Chihuahuan Desert gypsophiles. We investigated whether leaf chemistry of gypsophile lineages from the northern Chihuahuan Desert are similar to leaves of related nonendemic (gypsovag) species relative to their soil chemistry. We expected widely distributed gypsophiles (hypothesized to be older lineages on gypsum) would have distinct leaf chemistry from narrowly distributed, relatively younger lineages endemic to gypsum and gypsovags, reflecting adaptation to gypsum.METHODS:We collected leaves from 23 gypsophiles and related nonendemic taxa growing on nongypsum soils. Soils and leaves were analyzed for Ca, S, Mg, K, N, and P. Leaf gypsum was assessed using Fourier transform infrared spectroscopy.KEY RESULTS:Most widespread gypsophile lineages that are hypothesized to be relatively old accumulate foliar S, Ca, and gypsum, but younger gypsophile lineages and closely related gypsovags do not. Young, narrowly distributed gypsophile lineages have leaf chemical signatures similar to nonendemic congeners and confamilials.CONCLUSIONS:Our data suggest multiple adaptive mechanisms support life on gypsum in Chihuahuan Desert gypsophiles. Most widespread gypsophiles are specialized for life on gypsum, likely due to shared abilities to accumulate and assimilate S and Ca in leaves. In contrast, narrowly distributed gypsophiles may have mechanisms to exclude excess S and Ca from their leaves, preventing toxicity. Future work will investigate the nutrient accumulation and exclusion patterns of other plant organs to determine at what level excess S and Ca uptake is restricted for young-lineage gypsophiles and gypsovags.

Soil microbial communities control critical ecosystem processes such as decomposition, nutrient cycling, and soil organic matter formation. Continental scale patterns in the composition and functioning of microbial communities are related to climatic, biotic, and edaphic factors such as temperature and precipitation, plant community composition, and soil carbon, nitrogen, and pH. Although these relationships have been well explored individually, the examination of the factors that may act directly on microbial communities vs. those that may act indirectly through other ecosystem properties has not been well developed. To further such understanding, we utilized structural equation modeling (SEM) to evaluate a set of hypotheses about the direct and indirect effects of climatic, biotic, and edaphic variables on microbial communities across the continental United States. The primary goals of this work were to test our current understanding of the interactions among climate, soils, and plants in affecting microbial community composition, and to examine whether variation in the composition of the microbial community affects potential rates of soil enzymatic activities. A model of interacting factors created through SEM shows several expected patterns. Distal factors such as climate had indirect effects on microbial communities by influencing plant productivity, soil mineralogy, and soil pH, but factors related to soil organic matter chemistry had the most direct influence on community composition. We observed that both plant productivity and soil mineral composition were important indirect influences on community composition at the continental scale, both interacting to affect organic matter content and microbial biomass and ultimately community composition. Although soil hydrolytic enzymes were related to the moisture regime and soil carbon, oxidative enzymes were also affected by community composition, reflected in the abundance of soil fungi. These results highlight that soil microbial communities can be modeled within the context of multiple interacting ecosystem properties acting both directly and indirectly on their composition and function, and this provides a rich and informative context with which to examine communities. This work also highlights that variation in climate, microbial biomass, and microbial community composition can affect maximum rates of soil enzyme activities, potentially influencing rates of decomposition and nutrient mineralization in soils.

Background and aims Competition from the annual grass Bromus tectorum threatens aridland perennial bunchgrass communities. Unlike annuals, perennials must allocate part of their first year nitrogen (N) budget to storage rather than growth, potentially placing them at a competitive disadvantage. Methods We evaluated N acquisition and conservation for two perennial bunchgrasses, Agropyron desertorum and Pseudoroegneria spicata , at the seedling stage to investigate potential trade-offs between storage and growth when grown with and without B. tectorum under two levels of soil N. Results Agropyron desertorum had higher growth rates, N uptake, and N productivity than P. spicata when grown without B. tectorum , but trait values were similarly low for both species under competition. Without competition, N resorption was poor under high soil N, but it was equally proficient among species under competition. Conclusions A. desertorum had higher growth rates and N productivity than P. spicata without competition, suggesting these traits may in part promote its greater success in restoration programs. However, B. tectorum neighbors reduced its trait advantage. As plant traits become more integral to restoration ecology, understanding how N capture and conservation traits vary across candidate species and under competition may improve our ability to select species with the highest likelihood of establishing in arid, nutrient-limited systems.

PREMISE OF THE STUDY:Functional trait plasticity in resource capture traits has been suggested as an underlying mechanism promoting invasive species establishment and spread. Earlier studies on this mechanism treat invasiveness as a discrete characteristic (i.e., invasive vs. noninvasive) and do not consider the potential impacts of evolutionary history. In the present study, we used a continuous measure of invasiveness and a phylogenetic framework to quantify the relationship between functional trait expression, plasticity, and invasiveness in Rosa.METHODS:In a manipulative greenhouse experiment, we evaluated how light availability affects functional traits and their plasticity in Rosa sp. and the out-group species, Potentilla recta, which vary in their invasiveness.KEY RESULTS:Across functional traits, we found no significant relationship between plasticity and invasiveness. However, more invasive roses demonstrated an ability to produce a more branched plant architecture, promoting optimal light capture. Invasiveness also was linked with lower photosynthetic and stomatal conductance rates, leading to increased water-use efficiency (WUE) in more invasive roses.CONCLUSIONS:Our results suggest that functional trait values, rather than plasticity, promote invasive rose success, counter to earlier predictions about the role of plasticity in invasiveness. Furthermore, our study indicates that invasive roses demonstrate key functional traits, such as increased WUE, to promote their success in the high-light, edge habitats they commonly invade.

Maintaining self-sustaining populations of desired plants is fundamental to rangeland management, and understanding the relationships among plant growth, seed production, and seedling recruitment is critical to these efforts. Our objective was to evaluate how changes in maternal plant soil resource environment influences maternal plant biomass and seed production and seedling fitness in three widespread perennial bunchgrass species (Elymus elymoides [Raf.] Sezey, bottlebrush squirreltail; Festuca idahoensis Elmer, Idaho fescue; and Pseudoroegneria spicata [Pursh] A. Löve, bluebunch wheatgrass). We supplied water and nutrients to adult plants growing in the field and measured their productivity and fecundity. Then, in the laboratory, growth chamber, and field we assessed effects of the maternal water and nutrient additions on offspring performance. Across the three study species, vegetative traits were more plastic than reproductive traits, with resource addition measurably increasing plant growth but not seed production. Germination was high in both the laboratory and field across treatments, although seeds from irrigated maternal plants tended to have higher field germination. Seedling relative growth rate, leaf mass ratio, and relative root elongation rate (RRER) were highly variable, although RRER tended to be higher in seedlings derived from irrigated maternal plants. In the field, seedling survivorship was low across all species, but survivorship doubled in seedlings produced by P. spicata plants that received additional water through the growing season. Overall, our results suggest that biomass production and fecundity responses to nutrients are decoupled in the species and environment tested but maternal effects can have significant, although variable, impacts in some grassland species. As a result, biomass responses to natural and anthropogenic changes in resource availability may not be strong predictors of how altered resource supply may ultimately influence plant community dynamics in aridland systems.

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 lowresource availability following establishment from asexual fragments. Because polyploids are expected to have wider niche breadths than diploid ancestors, we predicted that a decaploid species would have superior ability to maximize resource uptake and use, and outperform a diploid congener when colonizing environments with contrasting light and nutrient availability. A mesocosm experiment was designed to test the main and interactive effects of ploidy (diploid and decaploid) and soil nutrient availability (low and high) nested within light environments (shade and sun) of two invasive aquatic plant congeners. Counter to our predictions, the diploid congener outperformed the decaploid in the early stage of growth. Although growth was similar and low in the cytotypes at low nutrient availability, the diploid species had much higher growth rate and biomass accumulation than the polyploid with nutrient enrichment, irrespective of light environment. Our results also revealed extreme differences in time to anthesis between the cytotypes. The rapid growth and earlier flowering of the diploid congener relative to the decaploid congener represent alternate strategies for establishment and success.