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Grime's strategies (competitor, stress tolerator, ruderal; CSR) represent viable trait combinations with which species deal with environmental conditions. CSR strategies are broadly used to understand plant adaptation to the environment, yet their plastic responses have received little attention. A globally‐calibrated tool (StrateFy) estimates CSR strategies using specific leaf area (SLA), leaf dry matter content (LDMC) and leaf area (LA) data, but these three traits can hardly characterise whole‐plant responses to the environment individually. CSR strategies reflect tradeoffs among growth, survival and reproduction, at both leaf and whole‐plant levels, thus integrating several functions. We hypothesised that CSR strategies and the three constituent traits would show independent plasticity patterns, and that CSR strategies would be more likely to show adaptive responses, i.e. to fit expected functional responses to environmental gradients. We compared phenotypic plasticity to drought in single traits (SLA, LDMC and LA) with the integrated plasticity of the resulting CSR strategy. The study species was the invasive plant Mesembryanthemum crystallinum, which is distributed in arid and semiarid Chile. We found that trait plasticity was rather idiosyncratic and contrary to what would be expected from a functional adjustment to drought: LDMC did not change (expected response: increase) and SLA increased (expected response: decrease). Conversely, plastic responses of CSR strategy and LA were consistent with functionally adaptive responses to drought in all populations: S‐strategy increased, while C‐strategy and LA decreased. We advocate the use of Grime's CSR theory as an integrative approach to further our understanding of adaptive plasticity in plants. [ABSTRACT FROM AUTHOR]

Climate change is expected to promote biological invasions. Invasive species often undergo adaptive evolution, but whether invasive species show greater evolutionary potential than their native counterparts under climate change has rarely been evaluated. We conducted experimental evolution trials comparing the evolution of physiological performance (light‐saturated photosynthetic rate, Amax) of coexisting and closely related (1) invasive‐native species pairs from Arid, Alpine, and Antarctic ecosystems, and (2) an invasive‐naturalized species pair from a Mediterranean ecosystem differing in invasiveness. Experiments were conducted over three generations and under four environments of temperature and water availability resembling typical and climate change conditions in each ecosystem. Amax increased across generations for most species. Invasive species from Arid, Alpine, and Antarctic ecosystems showed similar, greater, and lesser evolution of Amax than their native counterparts, respectively. The Mediterranean invasive species showed greater evolution of Amax than its naturalized congener. Similar patterns were observed in all four experimental environments for each ecosystem, suggesting that comparable responses may be expected under climate change scenarios. All study species showed a positive association between Amax and reproductive output. Results suggest that invasive plants and their native (or naturalized) counterparts would show similar evolutionary responses of physiological performance to global warming and drought. [ABSTRACT FROM AUTHOR]

A key process determining community assembly is habitat filtering, which reduces the range of trait values and thus leads to trait convergence. Habitat filtering is often assumed to involve a reduction in species richness, but such trait convergence could also result from phenotypic plasticity. By allowing more species in the community to show the 'right' phenotype and pass the filter, phenotypic plasticity could maintain species richness despite trait convergence. If phenotypic plasticity plays this role, environmental changes should modify trait distribution but not species composition or richness. We tested this hypothesis in a forest edge community recently invaded by the alien shrub Rubus praecox. We measured functional traits beneath Rubus canopy (Rubus‐invaded community) and in adjacent microsites naturally free from Rubus (original community), comparing trait dispersion and community structure parameters. We also characterized the microenvironments to seek functional explanations for the observed phenotypic changes. The functional dispersion parameter FDis showed habitat filtering in the Rubus‐invaded community (trait convergence), while in the original community it did not differ from a null model. Species richness and composition did not differ between the two communities. Soil characteristics were similar in both communities but light availability was greatly reduced in the Rubus‐invaded community. A principal component analysis of community‐weighted means of functional traits showed that phenotypic changes between communities were mostly consistent with functional responses to shading, including an increase in specific leaf area and a reduction in flavonoid concentration in the Rubus‐invaded community. We verified the conditions necessary to infer that phenotypic plasticity mediates the outcome of habitat filtering driven by Rubus in the study system, i.e. plasticity would explain species persistence despite trait convergence. Phenotypic plasticity, often subsumed within intraspecific variation in community assembly studies, should be considered individually to improve our understanding of the causes and consequences of habitat filtering. [ABSTRACT FROM AUTHOR]

The biotic resistance hypothesis asserts that native species may hinder the invasion of exotic species, which can occur either directly or indirectly by influencing interactions between exotic and local species. Aphid-tending ants may play a key role in the indirect biotic resistance to plant invasion. Ants may protect aphids, thus increasing their negative effect on exotic plants, but may also deter chewing herbivores, thus benefiting exotic plants. We studied native aphid-tending ants (Dorymyrmex tener, Camponotus distinguendus, and Dorymyrmex richteri) on exotic nodding thistles (Carduus thoermeri), which are attacked by thistle aphids (Brachycaudus cardui) and thistle-head weevils (Rhinocyllus conicus). We evaluated the impact of ants, aphids, and weevils on thistle seed set. We compared ant species aggressiveness towards aphid predators and weevils and performed ant-exclusion experiments to determine the effects of ants on aphid predators and weevils. We analysed whether ant species affected thistle seed set through their effects on aphids and/or weevils. The ant D. tener showed the most aggressive behaviour towards aphid predators and weevils. Further, D. tener successfully removed aphid predators from thistles but did not affect weevils. Excluding D. tener from thistles increased seed set. Analyses supported a negative indirect pathway between the aggressive D. tener and thistle seed set through aphid populations, while the other ant species showed no indirect effects on thistle reproduction. Therefore, aggressive aphid-tending ants may enhance biotic resistance by increasing aphid infestation on exotic invasive plants. This study highlights the importance of indirect biotic resistance in modulating the success of invasive species. [ABSTRACT FROM AUTHOR]

Aims Successful invasive plants are often assumed to display significant levels of phenotypic plasticity. Three possible strategies by which phenotypic plasticity may allow invasive plant species to thrive in changing environments have been suggested: (i) via plasticity in morphological or physiological traits, invasive plants are able to maintain a higher fitness than native plants in a range of environments, including stressful or low-resource habitats: a 'Jack-of-alltrades' strategy; (ii) phenotypic plasticity allows the invader to better exploit resources available in low stress or favorable habitats, showing higher fitness than native ones: a 'Master-of-some' strategy and (iii) a combination of these abilities, the 'Jack-and-Master' strategy. Methods We evaluated these strategies in the successful invader Taraxacum officinale in a controlled experiment mimicking natural environmental gradients. We set up three environmental gradients consisting of factorial arrays of two levels of temperature/light, temperature/water and light/water, respectively. We compared several ecophysiological traits, as well as the reaction norm in fitness-related traits, in both T. officinale and the closely related native Hypochaeris thrincioides subjected to these environmental scenarios. Important Findings Overall, T. officinale showed significantly greater accumulation of biomass and higher survival than the native H. thrincioides, with this difference being more pronounced toward both ends of each gradient. T. officinale also showed significantly higher plasticity than its native counterpart in several ecophysiological traits. Therefore, T. officinale exhibits a Jack-and-Master strategy as it is able to maintain higher biomass and survival in unfavorable conditions, as well as to increase fitness when conditions are favorable. We suggest that this strategy is partly based on ecophysiological responses to the environment, and that it may contribute to explaining the successful invasion of T. officinale across different habitats. [ABSTRACT FROM AUTHOR]

Questions The impact of invasive species on community structure and function varies, yet it is difficult to predict. Different hypotheses have been proposed to predict invasive species establishment and impact on resident communities, based on characteristics of the resident community and/or environmental conditions. Invasive species, however, interact with both native and exotic species. The interaction with exotic species is important, as it can result in secondary invasion or greater impact on native species. Smooth brome ( Bromus inermis Leyss.) is a widely planted forage crop, but also a harmful invasive species in North American grasslands, yet little is known about the variability of its impact on resident communities. We ask (1) whether smooth brome has a consistent impact on community structure and function; (2) which biotic and abiotic conditions are associated with smooth brome's impact on resident communities; and (3) whether smooth brome has a similar impact on native and exotic species, and which biotic or abiotic conditions drive the interaction of smooth brome with native and exotic species. Location Eight grasslands throughout Alberta, Canada. Methods We used space-for-time substitutions to quantify smooth brome's impact on different aspects of community structure and function, and whether it varies depending on species richness, productivity, temperature, precipitation and variation in precipitation. Results Smooth brome had a consistent negative impact on community structure and function. However, the strength of the effect depended on aspects of the local community. Smooth brome impacts on species richness were higher in species-rich areas, while impact on resident species biomass was larger in productive, warmer and more variable sites. In most sites the negative effect of smooth brome on species richness was higher for native species, compared to exotics. Impact on native and exotic species richness was larger in species-rich and more variable sites, respectively. Conclusions Understanding and predicting smooth brome's impact on community structure and function can help managers prescribe management plans to reduce negative impacts of smooth brome on native communities. Predicting the interaction of smooth brome with exotic species may be just as important when planning management strategies, to avoid secondary invasion and/or the accumulation of exotic species. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity is commonly considered as a trait associated with invasiveness in alien plants because it may enhance the ability of plants to occupy a wide range of environments. Although the evidence of greater phenotypic plasticity in invasive plants is considerable, it is not yet conclusive. We used a meta-analysis approach to evaluate whether invasive plant species show greater phenotypic plasticity than their native or non-invasive counterparts. The outcome of such interspecific comparisons may be biased when phylogenetic relatedness is not taken into account. Consequently, species pairs belonged to the same genus, tribe or family. The meta-analysis included 93 records from 35 studies reporting plastic responses to light, nutrients, water, CO2, herbivory and support availability. Contrary to what is often assumed, overall, phenotypic plasticity was similar between invasive plants and native or non-invasive closely related species. The same result was found when separate analyses were conducted for trait plasticity to nutrients, light and water availability. Thus, invasive plant species and their native or non-invasive counterparts are equally capable of displaying functional responses to environmental heterogeneity. The colonization of a wide range of environments by invasive plants could be due to their capacity to undergo adaptive ecotypic differentiation rather than to their ability to display plastic responses. Alternatively, phenotypic plasticity might play a role in plant invasion, but only during the initial phases, when tolerance of the novel environment is essential for plant survival. Afterwards, once alien plants are identified as invaders, the magnitude of phenotypic plasticity might be reduced after selection of the optimum phenotypes in each habitat. The identification of plant traits that consistently predict invasiveness might be a futile task because different traits favor invasiveness in different environments. Approaches at the local scale, focusing on the ecology of specific invasive plants, could be more fruitful than global macro-analyses. [ABSTRACT FROM AUTHOR]

Global change drivers create new environmental scenarios and selective pressures, affecting plant species in various interacting ways. Plants respond with changes in phenology, physiology, and reproduction, with consequences for biotic interactions and community composition. We review information on phenotypic plasticity, a primary means by which plants cope with global change scenarios, recommending promising approaches for investigating the evolution of plasticity and describing constraints to its evolution. We discuss the important but largely ignored role of phenotypic plasticity in range shifts and review the extensive literature on invasive species as models of evolutionary change in novel environments. Plasticity can play a role both in the short-term response of plant populations to global change as well as in their long-term fate through the maintenance of genetic variation. In new environmental conditions, plasticity of certain functional traits may be beneficial (i.e., the plastic response is accompanied by a fitness advantage) and thus selected for. Plasticity can also be relevant in the establishment and persistence of plants in novel environments that are crucial for populations at the colonizing edge in range shifts induced by climate change. Experimental studies show taxonomically widespread plastic responses to global change drivers in many functional traits, though there is a lack of empirical support for many theoretical models on the evolution of phenotypic plasticity. Future studies should assess the adaptive value and evolutionary potential of plasticity under complex, realistic global change scenarios. Promising tools include resurrection protocols and artificial selection experiments. [ABSTRACT FROM AUTHOR]

Invasive species can alter the structure and function of the communities they invade, as well as lead to biotic homogenization across their invasive range, thus affecting large‐scale diversity patterns. The mechanisms by which invasive species can lead to biotic homogenization are poorly understood. We argue that invasive species acting as strong, deterministic, and consistent filters within and across invaded communities are likely to cause biotic homogenization at multiple spatial scales. We studied Bromus inermis Leyss. invasion into eight grasslands covering most of the grassland and parkland natural regions of Alberta (western Canada). Specifically, we tested whether B. inermis (1) has a strong impact on species richness and composition, (2) consistently alters resources (nutrients, light, and soil moisture), imposing the same ecological filter to species establishment and persistence across sites, and hence (3) whether it leads to biotic homogenization within and across sites. We recorded plant cover and resources across native‐to‐invaded transition areas combining space‐for‐time substitutions with time‐series data analyses. Bromus inermis invasion was associated with rapid biotic homogenization of communities, within and among the eight grasslands. The sharp changes in species relative abundances following invasion was the initial driver of biotic homogenization, and species loss was delayed. Supporting the idea that biotic homogenization can occur when an invasive species presents a broad and consistent filter, resources modified by B. inermis invasion (particularly light and certain nutrients) were altered rather consistently within and across sites. The 50% reduction in light was likely the initial driver of biotic homogenization, and the increase in nutrient availability probably facilitates the displacement of species from the invaded areas and could lead to the establishment of self‐reinforcing dynamics. Overall, our results support the idea that invaders acting as strong, deterministic, and consistent ecological filters are likely to cause biotic homogenization of the communities they invade. [ABSTRACT FROM AUTHOR]

Rapid local adaptation frequently occurs during the spread of invading species. It remains unclear, however, how consistent, and therefore potentially predictable, such patterns of local adaptation are. One approach to this question is to measure patterns of local differentiation in functional traits and plasticity levels in invasive species in multiple regions. Finding consistent patterns of local differentiation in replicate regions suggests that these patterns are adaptive. Further, this outcome indicates that the invading species likely responds predictably to selection along environmental gradients, even though standing genetic variation is likely to have been reduced during introduction. We studied local differentiation in the invasive annual plant Erodium cicutarium in two invaded regions, California and Chile. We collected seeds from across strong gradients in precipitation and temperature in Mediterranean-climate parts of the two regions (10 populations per region). We grew seeds from maternal families from these populations through two generations and exposed the second generation to contrasting levels of water and nutrient availability. We measured growth, flowering time and leaf functional traits across these treatments to obtain trait means and plasticity measures. We found strong differentiation among populations in all traits. Plants from drier environments flowered earlier, were less plastic in flowering time and reached greater size in all treatments. Correlations among traits within regions suggested a coordinated evolutionary response along environmental gradients associated with growing season length. There was little divergence in traits and trait intercorrelations between regions, but strongly parallel divergence in traits within regions. Similar, statistically consistent patterns of local trait differentiation across two regions suggest that local adaptation to environmental gradients has aided the spread of this invasive species, and that the formation of ecotypes in newly invaded environments has been relatively consistent and predictable. [ABSTRACT FROM AUTHOR]

Several interspecific studies have related functional traits to alien plant invasiveness. Few studies have explicitly addressed how intraspecific variation in functional traits influences alien plant distribution across environments. In an old-growth temperate rainforest, we evaluated alien plant distribution across the light gradient, its relationship with native plant diversity and abundance, and variation in functional traits related to light capture that could explain the ecological breadth of alien plant species across the light gradient. In addition, we estimated possible ecological and phylogenetic constraints to intraspecific variation in these functional traits. In sixty 8-m 2 plots we recorded light availability together with richness and abundance of alien and native plant species. We measured in 14 alien plant species three functional traits (specific leaf area, chlorophyll content and root/shoot ratio) and calculated their coefficient of variation. We estimated ecological constraints by measuring correlations among traits that could limit functional responses to light. We assessed phylogenetic constraints by calculating the phylogenetic signal of those functional traits. Richness and abundance of alien plant species were positively associated with light availability, while abundance was negatively related to native plant species abundance. Dominance of alien species increased with light availability, but some of them were dominant even in the shade. Phenotypic variation of functional traits was positively associated with ecological breadth and dominance of alien plant species. We found little evidence of ecological or phylogenetic constraints on functional trait variation. Light availability and functional trait variation correlated with the distribution and dominance of alien plants in this temperate rainforest. Alien plant species showed considerable phenotypic variation in low light, which may facilitate colonization of the forest understory. This process would not be hindered by ecological or phylogenetic constraints. Intraspecific variation in functional traits can render insightful information on current and future alien plant distribution across environmental gradients. [ABSTRACT FROM AUTHOR]