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Background and Aims In the subfamily Poöideae (Poaceae), certain grass species possess anti-herbivore alkaloids synthesized by fungal endophytes that belong to the genus Epichloë (Clavicipitaceae). The protective role of these symbiotic endophytes can vary, depending on alkaloid concentrations within specific plant–endophyte associations and plant parts. Methods We conducted a literature review to identify articles containing alkaloid concentration data for various plant parts in six important pasture species, Lolium arundinaceum , Lolium perenne , Lolium pratense , Lolium multiflorum | Lolium rigidum and Festuca rubra , associated with their common endophytes. We considered the alkaloids lolines (1-aminopyrrolizidines), peramine (pyrrolopyrazines), ergovaline (ergot alkaloids) and lolitrem B (indole-diterpenes). While all these alkaloids have shown bioactivity against insect herbivores, ergovaline and lolitrem B are harmful for mammals. Key Results Loline alkaloid levels were higher in the perennial grasses L. pratense and L. arundinaceum compared to the annual species L. multiflorum and L. rigidum , and higher in reproductive tissues than in vegetative structures. This is probably due to the greater biomass accumulation in perennial species that can result in higher endophyte mycelial biomass. Peramine concentrations were higher in L. perenne than in L. arundinaceum and not affected by plant part. This can be attributed to the high within-plant mobility of peramine. Ergovaline and lolitrem B, both hydrophobic compounds, were associated with plant parts where fungal mycelium is usually present, and their concentrations were higher in plant reproductive tissues. Only loline alkaloid data were sufficient for below-ground tissue analyses and concentrations were lower than in above-ground parts. Conclusions Our study provides a comprehensive synthesis of fungal alkaloid variation across host grasses and plant parts, essential for understanding the endophyte-conferred defence extent. The patterns can be understood by considering endophyte growth within the plant and alkaloid mobility. Our study identifies research gaps, including the limited documentation of alkaloid presence in roots and the need to investigate the influence of different environmental conditions. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity can increase the extent of the environmental gradient occupied by a species (niche breadth) and modify the portion of niche space shared among co‐occurring species (niche overlap). Thus, phenotypic plasticity may play a role in community assembly processes. Given that plants deal with a multivariate environment, and that functional traits are often correlated, plastic responses to different environmental factors are likely correlated. However, the implications of correlations of plasticities for niche overlap remain unexplored. Here, we present and evaluate a conceptual framework that links correlations of plasticities and niche overlap patterns among co‐occurring plant species. We specifically tested in an arid shrubland whether positive, negative, or null correlations between plasticity to light and water availability would be associated with patterns of high, low, or random niche overlap, respectively. Field data identified light and water availability as key factors shaping herbaceous plant community structure. We estimated species' niche breadth and niche overlap using two‐dimensional kernel–density estimations (NOK) and standardised effect sizes of Pianka's niche overlap index (OSES). We measured phenotypic plasticity to light and water availability in the six most abundant species in a greenhouse experiment. We used the plasticity index (PI) to test 1) the relationship between plasticity to light and water availability, and 2) the association between overall plasticity (average PI across traits) and niche breadth. We found a positive relationship between plasticity to light and water availability. Increased overall plasticity was associated with a broader niche breadth. Both NOK and OSES estimations indicated a significant niche overlap pattern. Results supported one of the predictions of our conceptual framework: that a positive correlation of plasticities would lead to increased niche overlap. The verified conceptual framework broadens our understanding of the role of phenotypic plasticity in plant community coexistence. [ABSTRACT FROM AUTHOR]

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]

Parasitic plants and herbivores show similarities in their interactions with host plants. Herbivore‐induced resistance/susceptibility in plants can scale up to the arthropod community. Similar evidence regarding parasitic plants is scarce. We evaluated the indirect effects initiated by the mistletoe Tristerix aphyllus on the arthropod community of the cactus Echinopsis chiloensis in the Chilean coastal desert. Field observations suggested that a stem‐borer beetle bores more brood chambers in mistletoe‐parasitised cacti than in non‐parasitised cacti, and that arthropods colonise these chambers.We compared tissue toughness, chamber density and morphology in mistletoe‐parasitised and non‐parasitised cacti. We also compared richness, total abundance, abundance per taxa, diversity and composition of the colonising arthropod community.Parasitised cacti showed a 14% reduction in tissue toughness. Chamber density in parasitised cacti was four times greater and chambers were larger: 35% more volume, an entrance‐opening area 30% greater, and twice the area of the maximum‐width section. Arthropod species richness and diversity were higher in chambers of parasitised cacti. Arthropod community composition was different in chambers of parasitised and non‐parasitised cacti. Thus, spiders and moths were more abundant in parasitised cacti, and pseudoscorpions, scolopendras, ants and flies were exclusively present there, while non‐parasitised cacti had no exclusive taxa.Mistletoe infection results in a richer, more diverse and distinct arthropod community on its cactus host, which occurs through induced susceptibility to stem‐borers whose brood chambers are colonised by arthropods. Tristerix aphyllus could be a key‐stone species in these arid ecosystems, where arthropod diversity is relatively low. [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]

Disturbance by small mammals and shrub canopies are ecological factors typical of arid ecosystems that may influence plant invasion through environmental and community changes. Whereas disturbance beneath shrub canopies may promote invasion by removing dominant species, disturbance in open areas may hinder plant invasion by increasing environmental harshness. However, we are unaware of studies explicitly addressing the interactive effects of disturbance by mammals and shading by shrubs on community assembly processes to understand plant invasion. In an arid shrubland, disturbance and shading were caused by the fossorial rodent Spalacopus cyanus and the shrub Flourensia thurifera, respectively. We used functional dispersion data (trait convergence vs. divergence) and Grime´s theory (competitive, stress‐tolerant and ruderal strategies, CSR) to gain insights into the underlying assembly processes.We compared environmental conditions, richness and abundance of native and exotic species, as well as functional dispersion and prevalence of CSR‐strategies across four microsites (60 × 60 cm plots): undisturbed/open, undisturbed/shaded, disturbed/open and disturbed/shaded. We tested for functional differences between native and exotic species.Species richness was similar among microsites for both native and exotic species. Shading ameliorated environmental conditions, promoted trait divergence and increased prevalence of C‐ and R‐strategies. Disturbance increased the abundance of exotic species and removed dominant species in shaded microsites. Exotic and native species were functionally different: exotics showed shorter life span, lower height, thinner stems and smaller leaves than natives.Synthesis. Disturbance, by removing plant biomass, favoured exotic species in shaded microsites, where shrub canopy ameliorated environmental conditions and—by relaxing habitat filtering—promoted niche partitioning processes as well as C‐ and R‐strategies. We illustrate the value of linking trait‐based ecology approaches to micro‐environmental conditions, as it may provide insights into the underlying community processes when studying plant invasions at the local and microsite scales. Disturbed microsites beneath shrub canopies could be 'hotspots' where to concentrate efforts to manage plant invasions in arid ecosystems. [ABSTRACT FROM AUTHOR]

Background and Aims There is a paucity of empirical research and a lack of predictive models concerning the interplay between spatial scale and disturbance as they affect the structure and assembly of plant communities. We proposed and tested a trait dispersion-based conceptual model hypothesizing that disturbance reinforces assembly processes differentially across spatial scales. Disturbance would reinforce functional divergence at the small scale (neighbourhood), would not affect functional dispersion at the intermediate scale (patch) and would reinforce functional convergence at the large scale (site). We also evaluated functional and species richness of native and exotic plants to infer underlying processes. Native and exotic species richness were expected to increase and decrease with disturbance, respectively, at the neighbourhood scale, and to show similar associations with disturbance at the patch (concave) and site (negative) scales. Methods In an arid shrubland, we estimated species richness and functional dispersion and richness within 1 m2 quadrats (neighbourhood) nested within 100 m2 plots (patch) along a small-scale natural disturbance gradient caused by an endemic fossorial rodent. Data for the site scale (2500 m2 plots) were taken from a previous study. We also tested the conceptual model through a quantitative literature review and a meta-analysis. Key Results As spatial scale increased, disturbance sequentially promoted functional divergence, random trait dispersion and functional convergence. Functional richness was unaffected by disturbance across spatial scales. Disturbance favoured natives over exotics at the neighbourhood scale, while both decreased under high disturbance at the patch and site scales. Conclusions The results supported the hypothesis that disturbance reinforces assembly processes differentially across scales and hampers plant invasion. The quantitative literature review and the meta-analysis supported most of the model predictions. [ABSTRACT FROM AUTHOR]

Premise of research. Herbivore damage is generally higher in the sun than in the shade. The influence of shade tolerance on herbivory has been mainly related to the fact that light-demanding plant species show lower defense investments—and hence higher herbivory—than shade-tolerant species. The pattern of increased herbivory with increasing light availability may take different forms, depending on the drivers of herbivore damage across the light gradient: (1) herbivory pressure alone, (2) herbivory pressure together with plant resistance associated with shade tolerance, or (3) the two drivers seen in scenario 2 added to a differential effect of light availability on plant resistance depending on shade tolerance. Elucidating the specific patterns behind the general pattern of increased herbivory with increasing light availability may contribute to understanding and aid prediction of herbivory patterns in forest communities under natural or anthropogenic disturbance. Methodology. In a field study with 15 tree species distributed across the light gradient in a temperate rainforest (1.6%–26.2% canopy openness), we evaluated the relationship between canopy openness and seedling herbivory, with 755 seedlings surveyed for herbivore damage. Specifically, we evaluated the consistency between the observed herbivory–canopy openness relationship and the three scenarios described above. Pivotal results. We found steeper slopes for the herbivory–canopy openness relationship in tree species with lower shade tolerance; that is, we verified scenario 3. Conclusions. Shade tolerance determined the slope of the herbivory–canopy openness relationship across the light gradient. This finding expands our understanding of the recognized influence of shade tolerance on the interplay between herbivory and the light environment. [ABSTRACT FROM AUTHOR]

Background and Aims Disturbance often drives plant invasion and may modify community assembly. However, little is known about how these modifications of community patterns occur in terms of taxonomic, functional and phylogenetic structure. This study evaluated in an arid shrubland the influence of disturbance by an endemic rodent on community functional divergence and phylogenetic structure as well as on plant invasion. It was expected that disturbance would operate as a habitat filter favouring exotic species with short life cycles. Methods Sixteen plots were sampled along a disturbance gradient caused by the endemic fossorial rodent Spalacopus cyanus, measuring community parameters and estimating functional divergence for life history traits (functional dispersion index) and the relative contribution to functional divergence of exotic and native species. The phylogenetic signal (Pagel's lambda) and phylogenetic community structure (mean phylogenetic distance and mean nearest taxon phylogenetic distance) were also estimated. The use of a continuous approach to the disturbance gradient allowed the identification of non-linear relationships between disturbance and community parameters. Key Results The relationship between disturbance and both species richness and abundance was positive for exotic species and negative for native species. Disturbance modified community composition, and exotic species were associated with more disturbed sites. Disturbance increased trait convergence, which resulted in phylogenetic clustering because traits showed a significant phylogenetic signal. The relative contribution of exotic species to functional divergence increased, while that of natives decreased, with disturbance. Exotic and native species were not phylogenetically distinct. Conclusions Disturbance by rodents in this arid shrubland constitutes a habitat filter over phylogeny-dependent life history traits, leading to phylogenetic clustering, and drives invasion by favouring species with short life cycles. Results can be explained by high phenotypic and phylogenetic resemblance between exotic and native species. The use of continuous gradients when studying the effects of disturbance on community assembly is advocated. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity is a key mechanism by which plants respond to changing or heterogeneous conditions. Efforts to predict phenotypic plasticity across plant species have mainly focused on environmental variability or abiotic conditions, i.e. site characteristics. However, the considerable variation in phenotypic plasticity within sites calls for alternative approaches. Different functional groups are thought to differ in their plasticity levels. Further, traits such as leaf specific area (SLA), leaf area (LA) and maximum photosynthetic rate (Amax) reflect central aspects of plant strategies. Lower values of SLA, LA and Amax are indicative of a resource‐conservative strategy, which is thought to be associated with lower phenotypic plasticity. We used meta‐analytical data to test whether plant functional group (herbs, woody deciduous and woody evergreens) and SLA, LA and Amax are associated with phenotypic plasticity in four trait types: biomass allocation, plant size, leaf morphology and physiology. We obtained data from 168 plant species and accounted for phylogenetic relationships in all analyses. We found a positive relationship between SLA and phenotypic plasticity in biomass allocation, leaf morphology and physiology, with differences across functional groups. In contrast, there was no evidence of greater plasticity in plant size in species with higher SLA; rather the opposite was true for woody evergreens. Amax and LA showed similar, but less consistent associations with phenotypic plasticity. Our results show the potential of building predictive frameworks for phenotypic plasticity based on easily measured plant functional characteristics. Results also provide insights into plant strategies and suggest the existence of potential compromises: resource‐conservative, low‐SLA species tend to be more stress‐tolerant but may be less able to cope with variable conditions due to their generally lower phenotypic plasticity. Further studies are needed to explore the mechanisms and the potential implications of this association. [ABSTRACT FROM AUTHOR]

Predicting plastic responses is crucial to assess plant species potential to adapt to climate change, but little is known about which factors drive the biogeographical patterns of phenotypic plasticity in plants. Theory predicts that climatic variability would select for increased phenotypic plasticity, whereas evidence indicates that stressful conditions can limit phenotypic plasticity. Using a meta‐analytic, phylogeny‐corrected approach to global data on plant phenotypic plasticity, we tested whether latitude, climate, climatic variability and/or stressful conditions are predictors of plastic responses at a biogeographical scale. We found support for a positive association between phenotypic plasticity and climatic variability only for plasticity in allocation. Plasticity in leaf morphology, size and physiology were positively associated with mean annual temperature. We also found evidence that phenotypic plasticity in physiology is limited by cold stress. Overall, plant plastic responses to non‐climatic factors were stronger than responses to climatic factors. However, while climatic conditions were associated with plant plastic responses to climatic factors, they generally did not relate to plastic responses to other abiotic or biotic factors. Our study highlights the need to consider those factors that favour and limit phenotypic plasticity in order to improve predictive frameworks addressing plant species' potential to adapt to climate change. [ABSTRACT FROM AUTHOR]

The mechanisms behind the unique capacity of the vine Boquila trifoliolata to mimic the leaves of several tree species remain unknown. A hypothesis in the original leaf mimicry report considered that microbial vectors from trees could carry genes or epigenetic factors that would alter the expression of leaf traits in Boquila. Here we evaluated whether leaf endophytic bacterial communities are associated with the mimicry pattern. Using 16S rRNA gene sequencing, we compared the endophytic bacterial communities in three groups of leaves collected in a temperate rainforest: (1) leaves from the model tree Rhaphithamnus spinosus (RS), (2) Boquila leaves mimicking the tree leaves (BR), and (3) Boquila leaves from the same individual vine but not mimicking the tree leaves (BT). We hypothesized that bacterial communities would be more similar in the BR–RS comparison than in the BT–RS comparison. We found significant differences in the endophytic bacterial communities among the three groups, verifying the hypothesis. Whereas non-mimetic Boquila leaves and tree leaves (BT–RS) showed clearly different bacterial communities, mimetic Boquila leaves and tree leaves (BR–RS) showed an overlap concerning their bacterial communities. The role of bacteria in this unique case of leaf mimicry should be studied further. [ABSTRACT FROM AUTHOR]

Premise of research. Tolerance to herbivory is the capacity of plants to reduce the negative effects of damage on fitness. Increased growth rate and photosynthesis are two important mechanisms behind tolerance to herbivory. The chlorophyll fluorescence parameter F v / F m , which reflects photosynthetic performance, has been used to characterize stress effects on plants. Here, we tested the hypothesis that photosynthetic performance, estimated from F v / F m , may predict tolerance to herbivory. Methodology. In the greenhouse, we evaluated whether F v / F m values measured in recently damaged seedlings of the temperate rainforest tree Aextoxicon punctatum predict relative growth rate (RGR) measured 30 d after damage. RGR was earlier associated with tolerance to herbivory in tree species from this forest. In the field, we determined whether F v / F m values in experimentally damaged seedlings of 13 tree species are correlated with their reported levels of tolerance to herbivory. Pivotal results. RGR showed positive associations with F v / F m measured 3 h and 30 d after damage but no association with F v / F m measured before damage. In undamaged control seedlings, RGR was not related to F v / F m at any time evaluated. The across-species comparison in the field showed that F v / F m values were positively correlated with reported levels of tolerance to herbivory. Conclusions. The parameter F v / F m is an accurate predictor of RGR and tolerance to herbivore damage. We advocate the use of this rapid methodology to estimate plant tolerance to herbivory in natural populations. [ABSTRACT FROM AUTHOR]