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Global interest and investment in nature‐based solutions (NbS) are rapidly increasing because of the potential of this approach to concurrently counter biodiversity loss, provide cost‐effective measures for climate change adaptations, and maintain natural processes that underpin human health and wellbeing.Recognition is growing that grasslands in many regions will protect carbon stores more effectively than forests in the warmer, drier, more fire‐prone conditions of the future while also serving as hotspots for biodiversity. Yet grasslands have received less attention for their NbS potential. Despite the wide‐ranging goals of this approach, many investments in nature‐based solutions also have focused narrowly on using plants to meet climate pledges, often without considering plant interactions with herbivores and the abiotic environment that jointly control ecosystem functioning and underpin the success of nature‐based solutions.Here, we review the roles that large and small vertebrate and invertebrate herbivores play in the ability of the world's grasslands to provide nature‐based solutions, with a focus on wild herbivore impacts on biodiversity and carbon storage.Synthesis. Planning for nature‐based solutions with a holistic, ecologically informed view that includes the role of herbivores and their interaction with plants and the environment will allow NbS investments to more likely achieve successful, sustainable outcomes. [ABSTRACT FROM AUTHOR]

Natural selection on traits expressed repeatedly by individuals is usually investigated with a focus on mean values, although within‐individual trait distributions often differ also in other aspects, such as their spread and shape. In plants producing multiple flowers during a season, there might not be a single optimal flowering time, but rather an optimal distribution of flower opening dates. This optimal distribution might depend on both resource allocation patterns and interactions with the abiotic and biotic environment. In this study, we quantified mean, variance, skewness and kurtosis of 495 individual flowering schedules (5287 flowers) over 3 years, and assessed phenotypic selection on these aspects of the within‐individual distribution of opening dates in the perennial herb Lathyrus vernus. We also explored how selection on within‐individual variation in flowering schedules was related to effects on two fitness components: fruit set and the proportion of seeds escaping pre‐dispersal predation. Within‐individual variation in phenology was larger than, or at least similar to, among‐individual variation in all years. We found phenotypic selection on several aspects of individual flowering schedules. In 1 year, selection favoured plants with higher variance in opening dates, and this coincided with a higher fruit set in plants with an increased spread of the flowering schedule. In two of the study years, selection favoured a higher asymmetry of the flowering schedule, and plants with more right‐skewed distributions had higher fruit set and higher proportions of seeds escaping predation. Both fruit set and seed predation increased with an earlier mean flowering, resulting in no net selection on mean flowering date. Synthesis: Our results suggest that phenotypic selection on the spread and shape of flower opening date distributions might be at least as important as selection on the mean flowering date. In a broad sense, this implies that we should consider the entire trait distribution if we aim to understand the evolution of traits that are expressed multiple times within individuals. [ABSTRACT FROM AUTHOR]

Urbanization frequently alters the biotic and abiotic environmental context. Variation in both the biotic and abiotic environment can result in selection mosaics that lead to locally adapted phenotypes. Ecological changes to urban environments can result in evolutionary responses across a diverse array of plants and animals, but the effects of urbanization on local adaptation and coevolution between species remain largely unstudied.Using a common garden experiment of 30 populations and 1080 plants, we tested for local adaptation in the mutualism between white clover (Trifolium repens) and rhizobia (Rhizobium leguminosarum symbiovar trifolii) along an urbanization gradient. We asked: (Q1) are white clover and rhizobia locally adapted? (Q2) Does nitrogen (N) addition mediate the strength of local adaptation? (Q3) Is the strength of local adaptation in host plants related to the strength of local adaptation in rhizobia, as expected if white clover and rhizobia are coadapting? And (Q4) how does the degree of local adaptation vary with urbanization?We found evidence for local adaptation for both white clover and rhizobia, with stronger signatures of local adaptation for rhizobia than white clover (Q1). While N addition positively affected plant biomass and negatively affected nodule density, N addition did not consistently mediate patterns of local adaptation (Q2). The strength of local adaptation was positively related between white clover and rhizobia under N addition, suggesting that soil N mediates coadaptation between white clover and rhizobia (Q3). We did not find a consistent relationship between measures of urbanization and local adaptation (Q4). Additionally, fitness responses for white clover and rhizobia were unrelated to Rhizobium abundance and local adaptation was unrelated to the broader bacterial microbiome in the soil inoculants or root endosphere.Synthesis. Our results show a spatial mosaic in local adaptation, with stronger local adaptation for rhizobia than white clover. While urbanization does influence the ecology of plant–microbe interactions, our study suggests urbanization does not disrupt local adaptation and coevolution among mutualists. [ABSTRACT FROM AUTHOR]

Observed biodiversity–ecosystem function (BEF) relationships are highly variable, particularly in natural forests. However, our understanding of the factors that generate these often contradictory patterns, especially the role of different mycorrhizal associations, is still limited.By relating tree species richness and above‐ground biomass (AGB) in a fully mapped 24‐ha subtropical forest dynamics plot, we evaluated the impacts of soil fertility and tree mycorrhizal type in mediating BEF relationships at multiple spatial scales.Our results demonstrate a highly positive total richness effect on AGB for arbuscular mycorrhizal (AM) trees but a negative effect on AGB for ectomycorrhizal (EcM) trees, and their relationships were highly spatial scale dependent. However, the observed BEF relationships turned into positive at small spatial scales (i.e. 10 and 20 m) after controlling for other confounding factors (i.e. topography, soil fertility and AM proportion). In addition, we found significant interactions between soil fertility and species richness on AGB. Specifically, the positive effect of total species richness on AGB for major mycorrhizal types gradually weakened with increasing soil fertility, while the positive effect of EcM species richness on AM AGB gradually enhanced at small spatial scales, suggesting the observed diversity effects can be largely attributed to resource niche complementarity and the role of EcM fungi.Synthesis. We conclude that the variable BEF relationships among forest communities could be explained by spatial variation in abiotic environments and community mycorrhizal composition because different types of symbionts perform different nutrient uptake strategies and ability in protection from antagonists. Our findings provide novel insights into the understanding of the variation in the shape of BEF relationships in natural forests, which is critical for forest management, conservation and restoration in a changing world. [ABSTRACT FROM AUTHOR]

Litters of leaves and roots of different qualities occur naturally above‐ and below‐ground, respectively, where they decompose in contrasting abiotic and biotic environments. Therefore, ecosystem carbon (C) and nitrogen (N) dynamics can be strongly affected by the combination of litter position and quality. However, it is poorly understood how C versus N turnover of litters depend on the interplay among plant functional type (PFT), organs, traits and litter position.In a semi‐arid inland dune, soil surface and buried leaf litters and buried fine roots of 25 species across three PFTs (herbs, legume shrubs and nonlegume shrubs) were incubated for 3, 6, 9, 12, 18 and 24 months to investigate litter decomposition and C and N dynamics. Morphological and chemical (nutrient and NMR carbon) traits of initial litters of leaves and fine roots were determined.The litter decomposition rates (k values) of surface leaves and buried fine roots did not differ, but buried fine roots and buried leaf litter decomposed faster than surface leaf litter. Ratios of k values of surface leaves to buried leaves decreased with leaf C:N ratio. Herbs and legume shrubs decomposed faster than nonlegume shrubs for buried fine roots, but not for leaves. At given C loss, buried fine roots had higher N loss than leaf litters; legume shrubs with relatively higher N or lower C:N ratio had higher N loss than nonlegume shrubs. Stronger positive relationships between C and N losses were shown in leaves and legume shrubs than in fine roots and nonlegume shrubs respectively.Synthesis. The generality of faster N release of legume litters at given C release highlights the importance of legumes in N cycling in semi‐arid ecosystems where N is the limiting factor. The dynamics and coordination of C versus N release as a function of litter quality are modulated by litter position and PFT. These findings have important implications for the development of process‐based models on C and N cycles in the context of on‐going global change potentially altering the functional composition of plant communities and the relative quantities and qualities of above‐ground versus below‐ground litter. [ABSTRACT FROM AUTHOR]

The match between species trait values and local abiotic filters can restrict community membership. An often‐implicit assumption of this relationship is that abiotic filters select for a single locally optimal strategy, though difficulty in isolating effects of the abiotic environment from those of dispersal limitation and biotic interactions has resulted in few empirical tests of this assumption. Similar constraints have made it difficult to assess whether the type and intensity of abiotic filters shift along gradients of environmental harshness, as predicted by the stress‐dominance hypothesis.We planted 9,216 plants of 29 perennial grass and forb species that had a range of functional trait values and were assigned to a warm, intermediate or cool temperature tolerance pool across eight sites on the Colorado Plateau. We compared the distributions of traits of surviving individuals to null distributions to evaluate whether there were shifts in trait means and variation. Borrowing from phenotypic selection concepts in evolutionary biology, we assessed support for stabilizing, directional and disruptive abiotic filtering of trait distributions and whether these types of filtering varied with initial species pool.Functional composition was significantly different from null distributions for nearly all traits at all sites, with trait variation more restricted in harsher abiotic conditions, supporting the stress‐dominance hypothesis. Contrary to expectations, we primarily found evidence for directional selection, which increased in frequency in warm species pools while disruptive selection was found more often in cool and intermediate species pools.Synthesis. This study provides a controlled experimental approach to test the effect of the abiotic environment on plant trait filtering. We found that opportunistic strategies allowing for rapid water acquisition during favourable periods improved survival at warmer sites. Species with these strategies may be expected to benefit from increasing aridity and may be selected for active management efforts. More generally, the prevalence of directional selection may have important implications for dynamic vegetation models that rely on trait distributions for translating environmental variation into ecosystem processes. [ABSTRACT FROM AUTHOR]

So‐called fairy circles (FCs) comprise a spatially periodic gap pattern in arid grasslands of Namibia and north‐west Western Australia. This pattern has been explained with scale‐dependent ecohydrological feedbacks and the reaction‐diffusion, or Turing mechanism, used in process‐based models that are rooted in physics and pattern‐formation theory. However, a detailed ecological test of the validity of the modelled processes is still lacking.Here, we test in a spinifex‐grassland ecosystem of Western Australia the presence of spatial feedbacks at multiple scales. Drone‐based multispectral analysis and spatially explicit statistics were used to test if grass vitality within five 1‐ha plots depends on the pattern of FCs that are thought to be a critical extra source of water for the surrounding matrix vegetation. We then examined if high‐ and low‐vitality grasses show scale‐dependent feedbacks being indicative of facilitation or competition. Additionally, we assessed facilitation of grass plants for different successional stages after fire at fine scales in 1‐m2 quadrats. Finally, we placed soil moisture sensors under bare soil inside the FC gap and under plants at increasing distances from the FC to test if there is evidence for the 'infiltration feedback' as used in theoretical modelling.We found that high‐vitality grasses were systematically more strongly associated with FCs than low‐vitality grasses. High‐vitality grasses also had highly aggregated patterns at short scales being evidence of positive feedbacks while negative feedbacks occurred at larger scales. Within 1‐m2 quadrats, grass cover and mutual facilitation of plants was greater near the FC edge than further away in the matrix. Soil moisture after rainfall was lowest inside the FC with its weathered surface crust but highest under grass at the gap edge, and then declined towards the matrix, which confirms the infiltration feedback.Synthesis. The study shows that FCs are a critical extra source of water for the dryland vegetation, as predicted by theoretical modelling. The grasses act as 'ecosystem engineers' that modify their hostile, abiotic environment, leading to vegetation self‐organization. Overall, our ecological findings highlight the validity of the scale‐dependent feedbacks that are central to explain this emergent grassland pattern via the reaction‐diffusion or Turing‐instability mechanism. [ABSTRACT FROM AUTHOR]

The large majority of 'facilitation studies' focus on benefactor–beneficiary interactions. However, this may skew our view of the role of facilitation toward systems where it is most conspicuous, and perhaps toward harsh environments where discrete vegetation cover and pattern suggestive of facilitation are more common.Here we argue that a particular benefactor species is not required for facilitation to occur. Where vegetation cover is continuous, the community as a whole can ameliorate the abiotic conditions (community‐scale facilitative effect) and any species from the assembly experiencing stress (strain) could be facilitated. As a consequence, community‐scale facilitative effect might be generally common but often inconspicuous. Whether this community‐scale facilitative effect is influenced by particular characteristics of the vegetation cover is still largely unknown (e.g. biomass, species richness, functional composition and diversity).Expanding our research on facilitation beyond benefactor–beneficiary interactions and considering together the concept of community‐scale effect and strain might be key to progress our understanding of the general role of facilitation for species coexistence, ecosystem function, species distribution or climate change impact. [ABSTRACT FROM AUTHOR]

Climate change is shifting the distribution of species, and may have a profound impact on the ecology and evolution of species interactions. However, we know little about the impact of increasing temperature and changing rainfall patterns on the interactions between plants and their beneficial and antagonistic root symbionts.Here, we used a reciprocal multifactorial growth chamber experiment with seeds and soil microbial communities from three origins to investigate the impact of temperature and soil moisture on the growth, arbuscular mycorrhizal (AM) fungal colonization and root‐associated fungal community of a perennial herb. Moreover, we tested whether plants and AM fungi performed better or worse when plants were grown with their local soil biota, for example, due to plant adaptation or changes in the genetic or species composition of the soil microbial community.Temperature and soil moisture generally increased plant growth, whereas temperature but not soil moisture increased AM fungal colonization. The strength and direction of the plants' response to temperature were dependent on soil moisture and differed among plant populations, and AM fungal colonization was further affected by the origin of the soil microbial community. The root‐associated fungal community structure was impacted by temperature, soil moisture and the soil microbial origin, with interactive effects between the microbial origin and the abiotic environment. Plant biomass was lower when plants were grown with their local soil microbes, potentially due to intraspecific negative plant–soil feedbacks.Synthesis. Our findings indicate that, beyond a relatively uniform increase of plant growth and arbuscular mycorrhizal (AM) fungal colonization with increasing temperature, plants and root‐associated fungi of different origins will vary in their response to climate change (i.e. elevated temperature and shifts in rainfall). This may create pronounced, but difficult to predict, spatial and temporal variation in the ecology and evolution of plant–microbe interactions with a changing climate. [ABSTRACT FROM AUTHOR]

Timing of reproduction affects the outcome of interactions between plants and their pollinators, grazers and seed predators, as well as with their local abiotic environment. In seasonal environments, phenotypic selection has often been shown to favour early flowering. Yet, we still know little about the agents driving selection in natural populations and whether observed phenotypic selection corresponds to genotypic selection—a prerequisite for evolutionary change.In this study, we experimentally assessed phenotypic and genotypic selection for flowering time in a natural population of the perennial herb Lathyrus vernus. We transplanted sibling individuals, obtained through controlled crosses, to their source population and found net phenotypic selection for earlier flowering in the field.Despite a higher susceptibility to roe deer grazing, early‐flowering plants had higher fruit set and more seeds per fruit than late‐flowering plants. We found no support for genotypic selection on flowering time, and heritability for first flowering day was very low.Synthesis. Our results suggest that commonly observed patterns of higher fitness in early‐flowering plants do not always correspond to selection on genotypic values and are thus not necessarily expected to result in evolutionary change even if the relationship between flowering time and fitness is causal. This finding should be important to understand how species phenology might respond to changing environmental conditions. [ABSTRACT FROM AUTHOR]

Plant populations can exhibit local adaptation to their abiotic environment, such as climate and soil properties, as well as biotic components such as the chemical signatures of dominant plant species and mutualistic and pathogenic microbial populations. While patterns of local adaptation in individual species are widely recorded, the importance of microevolutionary processes for plant community assembly and function is poorly understood.Here, we examined how a history of long‐term co‐existence, and thus potential for local co‐adaptation, influenced the process of plant community assembly. Soil inocula and seeds of eight plant species were collected from three calcareous grasslands with a long history of grazing within a single geographical region. Mesocosm communities were established using local genotypes from a single site or an artificial mixture of genotypes from two different sites. To investigate the role of root exudates and local ('home') and non‐local ('away') soil biota as mediators of plant species co‐existence, the population origin treatment was combined with the addition of activated carbon, which is known to adsorb exudates from soil, and sterilization of soil inocula. Individual‐, species‐ and mesocosm‐level responses were measured over the course of three growing seasons.We found that root exudates promoted seedling survival, species co‐existence and productivity in assemblages of genotypes originating from the same community but had a weak impact in mixed, novel communities. Soil biota promoted the growth of subordinate forbs and restrained the growth of dominant graminoids, particularly in communities composed of local genotypes. The effects of population origin were significant in the first 2 years of the experiment but were not detectable in the third year when interbreeding and new seedling establishment took place. Plant genotypes coupled with 'home' microbial inoculum experienced a stronger reduction in growth compared with genotypes exposed to 'away' inoculum, indicating that plants experienced home‐field disadvantage in interactions with soil biota.Synthesis. Our study demonstrates that the mechanisms of initial grassland community assembly depend on community history, with below‐ground chemical interactions and plant interactions with soil biota becoming stronger drivers of dynamics in established and potentially co‐evolved communities. [ABSTRACT FROM AUTHOR]

Alpine plants occurring at high elevation are vulnerable to ongoing climate change, yet relatively little is known about the potential for high‐elevation species to adapt to changing environmental conditions. In particular, the extent to which high‐elevation plants will be able to resist predicted increases in the intensity of biotic interactions, such as herbivory, remains unclear.Species distributed across broad elevational ranges provide an opportunity to investigate evolutionary mechanisms and traits involved in adaptation to varying abiotic and biotic environments. This study focused on the perennial alpine plant Arabis alpina and combined field surveys and climate chamber experiments to test for intraspecific genetic divergence in traits related to growth and defence against herbivores. We screened multiple populations from low, intermediate and high elevations across a broad geographic area, characterising differences in growth form, leaf structural traits, palatability for herbivores and defensive chemistry. We then quantified the proportion of variation explained by elevation and population‐level effects.Our results document within‐species genetic divergence in multiple traits relevant for adaptation to the different abiotic and biotic pressures experienced at low and high elevations. Rates of herbivore damage declined with increasing elevation in the field, but plants from high‐ and intermediate‐elevation populations were generally more palatable for specialist herbivores than those from low‐elevation populations in feeding assays. Elevational clines were also observed in several glucosinolate defence compounds, and leaf herbivory more strongly induced glucosinolates in plants from high‐elevation populations than in those from low‐elevation populations. Leaf trichome density and growth form also diverged among populations contributing to growth–defence phenotypes associated with different elevations.However, populations from similar elevations often differed significantly in both growth‐ and defence‐related traits, with trait variation often better explained by population‐level effects than by elevation alone.Synthesis. Arabis alpina exhibits patterns of genetic variation in growth and defence traits consistent with adaptation to different elevations. However, populations from similar elevations also diverge in many of these ecologically relevant traits. Together, the extent of the observed trait variation suggests that this alpine species has considerable potential to adapt to a changing biotic environment. [ABSTRACT FROM AUTHOR]

Experimental warming in situ suggests that warming could lead to a loss of biodiversity. However, species that remain in situ and experience climate change will interact with species tracking climate change, which could also affect patterns of biodiversity. The relative contribution of species gains and losses to net changes in species richness is still unclear.We use transplanted plant communities to test the hypothesis that both the change in climate and ecological communities tracking climate change will influence how species richness responds to climate change. Three intact alpine plant communities were reciprocally transplanted to create scenarios in which species experienced warmer and wetter conditions (transferred to lower elevations) and cooler and drier conditions (transferred to higher elevations) over 10 years on the Tibetan Plateau. Communities transplanted into the same elevation as controls represent species tracking climate change.Transferring to lower elevations generally caused a net increase in richness and a higher rate of gains relative to the control plots; the magnitude of this effect depended on the specific elevation. Transferring to higher elevations lead to either net increases or decreases in richness and gains, depending on elevation. Species gains predicted much more variation in changes in species richness (50%) than did species loss (9%).Species richness at the receptor site and the donor site were both important predictors of variation in species richness, and the abiotic environment did not explain additional variation. Changes in cover of dominant plant species in response to transfers did not predict changes in species richness, species gain or species loss. Our results suggest that species gains from species tracking climate change at the receptor sites, rather than species loss from the donor sites, predicted changes in species richness.Synthesis. Warming experiments with physical barriers to dispersal may overestimate the negative effect of warming on plant diversity by not accounting for species gains. Our study highlights the importance of biotic factors in addition to the abiotic environment, when considering how climate change will affect plant diversity. [ABSTRACT FROM AUTHOR]

Interactions at multiple scales can shape how forest ecosystems respond to both climate change and disturbance. At landscape scales, feedbacks cause vegetation and wildfire regimes to alter one another, while forest patterns at local scales can result from feedbacks between plants and their abiotic environment. Consequently, disturbances and abiotic changes may give rise to forest patterns that further affect processes like wildfire.Examples may exist in the history of subalpine ribbon forests, which are alternating areas of forest and meadow where snow drifting and linear bands of trees depend upon each other. Just as ongoing climate changes may change snow levels and the dynamics in these forests, past climate changes and wildfires may have generated the conditions suitable for ribbon forests.To examine feedbacks in subalpine forests and the potential that climate changes and fires gave rise to ribbon forests, we obtained six fossil pollen records from a subalpine landscape in Colorado. Forests there may have responded to climate change and widespread wildfires ˜1,000 years ago when >80% of sites on the landscape burned within a century. The fires coincided with regional warming, but the extent of burning declined before the climate cooled, possibly driven by changes in fuel structure and composition.The pollen records indicate that large vegetation changes coincided with the widespread wildfires at five of the six sites. Pollen assemblages consistent with ribbon forests first became important at this time as sagebrush (Artemisia) and other meadow taxa increased and conifers, especially spruce (Picea) declined. The ribbon forests emerged as novel fuel breaks at the time when temperatures rose ˜0.5°C but the number of sites burned per century declined. Cooling during the Little Ice Age then expanded the openings and extent of ribbon forests, probably helping to reduce the frequency of fires across our sites to its minimum.Synthesis. The rise of ribbon forests in northern Colorado illustrates how climate and fire can interact to rapidly transform landscapes and disturbance regimes. The interactions can produce forest patterns with unexpected consequences such as reduced wildfire despite regional warming. [ABSTRACT FROM AUTHOR]

Abstract: Predicting the structure and dynamics of communities is difficult. Approaches linking functional traits to niche boundaries, species co‐occurrence and demography are promising, but have so far had limited success. We hypothesized that predictability in community ecology could be improved by incorporating more accurate measures of fine‐scale environmental heterogeneity and the context‐dependent function of traits. We tested these hypotheses using long term whole‐community demography data from an alpine plant community in Colorado. Species distributions along microenvironmental gradients covaried with traits important for below‐ground processes. Positive associations between species distributions across life stages could not be explained by abiotic microenvironment alone, consistent with facilitative processes. Rates of growth, survival, fecundity and recruitment were predicted by the direct and interactive effects of trait, microenvironment, macroenvironment and neighbourhood axes. Synthesis. Context‐dependent interactions between multiple traits and microenvironmental axes are needed to predict fine‐scale community structure and dynamics. [ABSTRACT FROM AUTHOR]

Abstract: Abiotic factors, biotic interactions and dispersal ability determine the spatial distribution of species. Theory predicts that abiotic constraints set range limits under harsh climatic conditions and biotic interactions set range limits under benign climatic conditions, whereas dispersal ability should limit both ends of the distribution. However, empirical studies exploring how these three components jointly affect species across environmental gradients are scarce. Here, we present a study that jointly examines these factors to investigate the constraints of the recruitment of Swiss stone pine (Pinus cembra) at and beyond its upper and lower elevational range limits in the Swiss Alps. We investigated the natural recruitment of pines and additionally conducted seed transplant experiments to test how much abiotic factors (mean summer and winter temperatures, soil moisture), biotic interactions (understorey vegetation cover, canopy cover, seed predation) and/or seed deposition by the spotted nutcracker (Nucifraga caryocatactes) affect pine establishment. We found significant effects of biotic interactions and seed deposition by spotted nutcrackers on the recruitment of Swiss stone pine at both the upper and lower elevational range, but could not detect significant effects of abiotic factors. Importantly, dispersal limitation rather than temperature and soil moisture restricted the recruitment of pines at the upper elevational range. Synthesis. Our study highlights the importance of biotic interactions and dispersal ability in setting the upper range limits of species that have been regarded as mainly controlled by climate. This suggests that potential range shifts of plants in response to climate warming may strongly depend on seed dispersal and biotic interactions and not only on climatic factors. [ABSTRACT FROM AUTHOR]

Reductions in community evenness can lead to local extinctions as dominant species exclude subordinate species; however, herbivores can prevent competitive exclusion by consuming otherwise dominant plant species, thus increasing evenness. While these predictions logically result from chronic, gradual reductions in evenness, rapid, temporary pulses of dominance may also reduce species richness. Short pulses of dominance can occur as biotic or abiotic conditions temporarily favour one or a few species, manifested as increased temporal variability (the inverse of temporal stability) in community evenness. Here, we tested whether consumers help maintain plant diversity by reducing the temporal variability in community evenness., We tested our hypothesis by reducing herbivore abundance in a detailed study of a developing, tallgrass prairie restoration. To assess the broader implications of the importance of herbivory on community evenness as well as potential mechanisms, we paired this study with a global herbivore reduction experiment., We found that herbivores maintained plant richness in a tallgrass prairie restoration by limiting temporary pulses in dominance by a single species. Dominance by an annual species in a single year was negatively associated with species richness, suggesting that short pulses of dominance may be sufficient to exclude subordinate species., The generality of this site-level relationship was supported by the global experiment in which inter-annual variability in evenness declined in the presence of vertebrate herbivores over timeframes ranging in length from 2 to 5 years, preventing declines in species richness. Furthermore, inter-annual variability of community evenness was also negatively associated with pre-treatment species richness., Synthesis. A loss or reduction of herbivores can destabilize plant communities by allowing brief periods of dominance by one or a few species, potentially triggering a feedback cycle of dominance and extinction. Such cycles may not occur immediately following the loss of herbivores, being delayed until conditions allow temporary periods of dominance by a subset of plant species. [ABSTRACT FROM AUTHOR]

Differential dispersal of plant and microbial propagules may result in the geographical disassociation of plant populations from their local abiotic conditions and microbial communities, especially in the face of species introductions and changing climates., To assess the potential consequences of disrupting historical relationships between plant populations, microbial communities and soil conditions, we grew Carpinus caroliniana seedlings from populations across the species range in combinations of sterilized soils and soil microbial communities, in soils collected from sites with or without conspecific trees. This controlled environment study simulated the consequences for seedling growth of independently or jointly disrupting the historical plant population-soil match, plant population-microbial community match and microbial community-soil match., Seedlings grown in soils from areas without conspecifics had lower biomass, but benefited from inoculation with their historical microbial communities. For conspecific-cultured soils, growth was optimized when seedlings grew with novel microbial communities, but only when microbial communities were local with respect to abiotic soil conditions. Correlative evidence suggests that this may stem from alignment of ectomycorrhizal fungal communities to abiotic soil conditions., Synthesis. Maintaining historical plant-microbial community relationships may benefit plant species spreading into new areas; however, for movement within current ranges, maintaining the historical relationship between microbial communities and the abiotic aspects of soils may have more important consequences for early growth. [ABSTRACT FROM AUTHOR]

Plants protect themselves against herbivore attacks through a myriad of physical structures and toxic secondary metabolites. Together with abiotic factors, herbivores are expected to modulate plant defence strategies within plant assemblages. Because the abundance of insect herbivore decreases in colder environments, the palatability of plants in communities at higher elevation should shift in response to both abiotic and biotic factors., We inventoried grasshopper communities to document changes in herbivore abundance along elevation gradients and quantified associated shifts in plant palatability. We measured plant palatability by measuring the growth of Spodoptera littoralis generalist caterpillars fed with the leaves of 172 plant species. We related plant palatability to leaf traits and elevation at the species and community levels., In congruence with the decrease in grasshopper abundance with elevation, we found that the mean palatability level of plant communities increases with elevation. In addition, plant palatability was negatively associated with the community-weighted mean of leaf dry matter content. At the species level, plants with high carbon-to-nitrogen ratio were less palatable, while we found no effect of species mean elevation on plant palatability., Synthesis. Our results suggest that plant communities at higher elevation are composed of species that are generally more palatable for insect herbivores. Shift in plant palatability with elevation may thus be the outcome of a relaxation of the in situ herbivore pressure and changes in abiotic conditions. [ABSTRACT FROM AUTHOR]

The leaf economics spectrum ( LES) describes global covariation in the traits of plant leaves. The LES is thought to arise from biophysical constraints and habitat filtering (ecological selection against unfit trait combinations along environmental gradients). However, the role of habitat filtering in generating the LES has not been tested experimentally., If the process of habitat filtering plays a role in generating the LES, the LES could weaken in communities that have yet to be filtered by the current environment, for example after abiotic environmental change. LES traits are commonly used to predict community and ecosystem processes, and if the LES weakens in unfiltered communities, LES-based models may no longer apply., In the glasshouse, we experimentally simulated three stages of habitat filtering in response to abiotic change: from unfiltered, to semi-filtered, to completely filtered communities. In each stage, we quantified the strength of the LES and assessed the accuracy of trait-based models of an important ecological process, pathogen infection., The strength of the LES increased with the completeness of habitat filtering, as did the accuracy of trait-based models of plant susceptibility to pathogen infection., Synthesis. Our results suggest that habitat filtering plays a fundamental role in strengthening the trait correlations of the LES and that trait-based models may be less accurate when communities have not been filtered by the current environment, for example, following rapid environmental change. [ABSTRACT FROM AUTHOR]

Co-fruiting plant species are subject to a variety of biotic and abiotic processes that may influence patterns of fruiting phenology and the functional and phylogenetic diversity of co-fruiting taxa in a community. Understanding the seasonal patterns of functional and phylogenetic diversity of fruiting in a community will shed new light on potential mechanisms structuring plant communities., Using rain forest trees in south-eastern Madagascar as our system, we predicted there would be clustering of fruit and seed traits and phylogenetic relationships among co-fruiting species because plants are vying for seed-dispersal services from a limited set of generalist frugivore taxa. We also predicted that seasonal variations in rainfall would mediate fluctuations in functional trait and phylogenetic diversity of co-fruiting assemblages., Despite fluctuating patterns in their functional trait diversity over time, co-fruiting assemblages displayed consistent clustering of fruit/seed traits across time. Phylogenetic diversity was not clustered overall, but fluctuated non-randomly in time, between clustered and overdispersed, such that strong shifts in rainfall were associated with the co-fruiting of more closely related species., Synthesis. We suggest that it may be more beneficial for co-fruiting plant species to share similar fruit and seed traits than to diversify traits, when they rely on a comparatively small set of generalist frugivorous taxa for seed dispersal. Results also demonstrate that rainfall-driven environmental filtering may cause seasonal fluctuations in the phylogenetic patterns of phenology in a community. Results highlight the importance of a temporal context in examining structural patterns of communities. [ABSTRACT FROM AUTHOR]

Despite the disproportionate influence that propagule production, dispersal, seed-to-seedling recruitment and vegetative reproduction can have on plant population and community dynamics, progress has been slow in the directed collection of regeneration traits to inform community assembly outcomes., While seed mass is globally available and linked to growth and reproductive output, there are limits to its explanatory ability. In this essay, we call for expanded efforts to integrate a more diverse set of regeneration traits into community assembly models., First, we extend an existing community assembly framework to conceptualize regeneration as a series of transitional processes whose outcomes are influenced by abiotic filters, biotic interactions and species traits. We then briefly review the literature, highlighting filters and traits of demonstrated or theorized importance for each transition. Finally, we place regeneration in the context of existing and emerging modelling approaches in trait-based community assembly, summarizing key areas of progress needed to integrate regeneration traits into these efforts., Synthesis. By incorporating influential regeneration traits into empirical studies and global data bases, we can begin to disentangle regenerative mechanisms underlying community assembly outcomes and enhance rapidly developing models of species' abundances, distributions and responses to environmental change. [ABSTRACT FROM AUTHOR]

Ecological theory indicates that warmer and more stable climates should result in stronger biotic interactions. Therefore, plant species growing at lower elevations and experiencing greater herbivore pressure should invest in higher levels of defences than those at higher elevations. Nonetheless, there are a number of studies that have found no effect of elevational gradients on plant defensive traits. Several factors might explain the lack of consistency for the altitude-defence relationships, including (i) the reduction of all defensive traits into one measure of resistance; (ii) not considering plant defence as the simultaneous expression of several defensive traits; and (iii) not considering the relative influence of biotic (e.g. herbivory) and abiotic (e.g. climate and soil conditions) factors associated with the ecological gradient., Here, we present a comprehensive test of the effects of elevation and its associated biotic and abiotic factors on the individual and simultaneous expression of constitutive direct and indirect defences and their inducibility (i.e. expression of defences after herbivore attack). Specifically, we estimated climatic and soil variables and measured herbivore damage and constitutive and jasmonic acid-induced glucosinolate levels in the leaves as a proxy for direct defences, and volatile emission as a proxy for indirect defences in 16 Cardamine species naturally growing along the steep elevational gradient of the Alps., Within a phylogenetic comparative framework, we found that species growing at lower elevations invested more in the simultaneous inducibility of both direct and indirect defences, whereas species growing at higher elevations invested more in constitutive direct defences. Although we found strong elevational gradients in herbivory and climatic and soil variables, these biotic and abiotic factors only partially explained elevational patterns in plant defences., Synthesis. These results highlight that the complex regulation of multiple defence traits strongly vary across elevational gradients and build towards a better understanding of the multiple mechanisms underlying trait evolution and species interactions along ecological gradients. [ABSTRACT FROM AUTHOR]

Understanding how intraspecific trait variability ( ITV) responds to both abiotic and biotic constraints is crucial to predict how individuals are assembled in plant communities, and how they will be impacted by ongoing global environmental change., Three key functional traits [plant height, leaf area ( LA) and specific leaf area ( SLA)] were assessed to quantify the range of ITV of four dominant plant species along a rainfall gradient in semi-arid Mediterranean shrublands. Variance partitioning and confirmatory multilevel path analyses were used to assess the direct and indirect effects of rainfall, space limitation (crowding) and neighbouring plant traits on ITV., The direct effect of the local neighbourhood on the trait values of subordinate individuals was as strong as the effect of rainfall. The indirect effect of rainfall, however, mediated by the effect of the local neighbourhood on the trait values of subordinate individuals, was weak. Rainfall decreased the height and SLA of subordinate individuals, but increased their LA. Neighbouring plant traits were just as strong predictors as crowding in explaining changes in ITV., Synthesis. Our study provides a framework to disentangle the direct effects of abiotic factors and their indirect effects on ITV mediated by the local neighbourhood. Our results highlight that abiotic and biotic constraints are both substantial sources of trait variations at the individual level, and can blur processes underlying changes in ITV. Considering and disentangling combined sources with an individual perspective would help to refine our predictions for community assembly and functional ecology. [ABSTRACT FROM AUTHOR]

Invasive species are detrimental ecologically and economically. Their negative impacts in Africa are extensive and call for a renewed commitment to better understand the correlates of invasion success., Here, we explored several putative drivers of species invasion among woody non-native trees and shrubs in southern Africa, a region of high floristic diversity. We tested for differences in functional traits between plant categories using a combination of phylogenetic independent contrasts and a simulation-based phylogenetic anova., We found that non-native species generally have longer flowering duration compared with native species and are generally hermaphroditic, and their dispersal is mostly abiotically mediated. We also revealed that non-native trees and shrubs that have become invasive are less closely related to native trees and shrubs than their non-invasive non-native counterparts. Non-natives that are more closely related to the native species pool may be more likely to possess traits suited to the new environment in which they find themselves and thus have greater chance of establishment. However, successful invaders are less closely related to the native pool, indicating evidence for competitive release or support for the vacant niche theory., Synthesis. Non-native trees and shrubs in southern Africa are characterized by a suite of traits, including long flowering times, a hermaphroditic sexual system and abiotic dispersal, which may represent important adaptations promoting establishment. We suggest that differences in the evolutionary distances separating the native species pool from invasive and non-invasive species might help resolve Darwin's naturalization conundrum. [ABSTRACT FROM AUTHOR]

The timing of tree flushing follows strong phenotypic and genetic clines across environmental gradients. It may be seen as an adaptive response to abiotic (escape of spring frost and maximizing growing season length) and biotic (escape of pest and disease) hazards. However, few studies have investigated jointly both types of hazards., We assessed exposure to both abiotic (spring frost) and biotic (powdery mildew) hazards within and between sessile oak populations along elevation gradients, during the flushing period in several years. For each population and phenological phenotype (early- vs. late-flushing trees), we estimated safety margins, defined as the time period separating budburst from the hazard occurrence (spore emission, spring frost)., We observed that powdery mildew phenology (initiation of spore release in spring) was less responsive to the elevation gradient than oak phenology (budburst) and that it was not correlated with tree phenology within populations. The spring frost and disease safety margins varied considerably between oak populations as a function of elevation and within populations in relation to tree phenological phenotype. For both hazards, safety margins decreased significantly with increasing elevation. The safety margin for spring frost was mostly positive (i.e. escape), whereas the safety margin for powdery mildew was mostly negative (i.e. exposure), leading to infection. The abiotic and biotic hazards interact in opposite directions with phenology, especially at low elevations (< 500 m) where early flushing enabled trees to escape disease while late flushing provided a higher safety margin against late frost., Synthesis. The observed patterns suggest that oak populations are better adapted to escape spring frost than pathogen exposure all along the elevation gradient. The combination of the biotic and abiotic selective pressures may have contributed to the maintenance of phenological diversity within low-elevation tree populations. As tree and pathogen respond differently to environmental cues, climate change is likely to affect the phenological (a)synchrony between host and parasite, both within and between populations. [ABSTRACT FROM AUTHOR]

There is a rising interest in the role of species diversity in ecosystem functioning and services, including productivity. Yet, how the diversity-productivity relationship depends on species identity and abiotic conditions remains a challenging issue., We analysed mixture effects on species productivity along site productivity gradients, calculated from a set of abiotic factors, in two biogeographic contexts (highlands and lowlands). We compared the productivity of 5 two-species mixtures (i.e. 10 cases of mixed species) with that of monocultures of the same species. Five main European tree species were considered: sessile oak ( Quercus petraea Liebl.), Scots pine ( Pinus sylvestris L.), European beech ( Fagus sylvatica L.), silver fir ( Abies alba Mill.) and Norway spruce ( Picea abies ( L.) H. Karst)., Our data set was compiled from the 2006 to 2010 French National Forest Inventory data base and covers 2361 plots including pure and mixed stands., Overall productivity of mixtures in highlands, that is European beech- Norway spruce, European beech-silver fir and to a lesser extent, silver fir- Norway spruce, was found to be higher than expected from the productivity of corresponding monospecific stands. Overyielding was mainly due to European beech for the first two mixtures and to silver fir for the third one., No effect of mixture was found for sessile oak- Scots pine and sessile oak- European beech stands in lowlands. Overyielding of sessile oak mixed with Scots pine was not strong enough to significantly increase overall stand productivity. Overyielding of European beech was balanced by an underyielding of sessile oak., The mixture effect changed along site productivity gradients for six cases out of the 10 studied, with a stronger and positive effect on sites with low productivity. The magnitude of this change along site productivity gradients varied up to 89% depending on the tree species., Synthesis. The nature of species interaction in mixtures with regard to productivity changes with species assemblage and abiotic conditions. Overyielding is strongest when species grow in highlands on less productive sites. A negative link between mixture effect and site productivity was found, in line with the stress-gradient hypothesis. [ABSTRACT FROM AUTHOR]

The question of the relative importance of biotic interactions versus abiotic drivers for structuring plant communities is highly debated but largely unresolved. Here, we investigate the relative importance of mean July air temperature, nitrogen (N) availability and direct plant interactions in determining the millennial-scale population dynamics through the Holocene (10 700-5200 cal. years bp) for four temperate tree taxa in the Scottish Highlands., A variety of dynamic population models were fitted to our palaeoecological time-series data to determine the mechanism(s) by which each driver affected the population biomass dynamics of Betula (birch), Pinus (pine), Alnus (alder) and Quercus (oak). Akaike information criterion weights identified the best model(s) for describing the relationship between each population and driver. The relative importance of these drivers was then assessed by the ability of each model to predict the observed population biomass dynamics. We also measured the change in goodness-of-fit of each model over time., We found that models of intra- and interspecific plant interactions described the plant population dynamics better than temperature- or N-dependent population growth models over the 5000-year study period. The best-fitting models were constant over time for pine, alder and oak. However, the plant-N availability and plant-temperature models provided a progressively better fit to the birch data when temperatures rose and N availability declined, suggesting increasing importance of these abiotic factors coincident with changing conditions., Synthesis. Multiple mechanistic models were applied to palaeoecological data to infer the most likely processes driving millennial-scale plant biomass dynamics in a woodland ecosystem. Direct plant interactions provided a better explanation for population biomass dynamics than growing season temperature or N availability over the full study period. The relative importance of all drivers we assessed here varied by species and - in the case of birch - over time in response to warming and reduced N availability. [ABSTRACT FROM AUTHOR]

The plant trait composition of forest fragments is thought to be partly determined by forest spatial properties, although the relative importance of habitat configuration and local abiotic drivers is poorly understood., To address this issue, large-scale habitat extent data were combined with detailed field survey information for temperate broad-leaved deciduous forest patches to quantify the relative effects of spatial and abiotic filters on plant community mean trait values., Local conditions such as shade and soil fertility had the largest effect on mean trait values, but aspects of habitat configuration also had significant partial effects on a number of traits., Mean trait values within older forest patches were more strongly influenced by forest spatial configuration than in younger patches., Synthesis. Results indicate that, in addition to the effects of greater light availability and competition in small patches and at forest edges, aspects of habitat configuration such as patch size and isolation are themselves important factors limiting the occurrence of forest specialist species. Large areas of core forest habitat contain a greater proportion of rare, poor dispersing species, although these effects were less visible in more recently established forest. This highlights the importance of maintaining existing large and old forest patches as a refuge for forest specialist plants. The results of this comparison of spatial and abiotic variables suggest that controlling the spatial properties of forest patches is likely to prove an effective way of managing plant species diversity, provided that sites with appropriate abiotic conditions are chosen. [ABSTRACT FROM AUTHOR]

Biotic interactions exert considerable influence on the distribution of individual species and should, thus, strongly impact communities. Implementing biotic interactions in spatial models of community assembly is therefore essential for accurately modelling assemblage properties. However, this remains a challenge due to the difficulty of detecting the role of species interactions and because accurate paired community and environment data sets are required to disentangle biotic influences from abiotic effects., Here, we incorporate data from three dominant species into community-level models as a proxy for the frequency and intensity of their interactions with other species and predict emergent assemblage properties for the co-occurring subdominant species. By analysing plant community and field-quantified environmental data from specially designed and spatially replicated monitoring grids, we provide a robust in vivo test of community models., Considering this well-defined and easily quantified surrogate for biotic interactions consistently improved realism in all aspects of community models (community composition, species richness and functional structure), irrespective of modelling methodology., Dominant species reduced community richness locally and favoured species with similar leaf dry matter content. This effect was most pronounced under conditions of high plant biomass and cover, where stronger competitive impacts are expected. Analysis of leaf dry matter content suggests that this effect may occur through efficient resource sequestration., Synthesis. We demonstrate the strong role of dominant species in shaping multiple plant community attributes, and thus the need to explicitly include interspecific interactions to achieve robust predictions of assemblage properties. Incorporating information on biotic interactions strengthens our capacity not only to predict the richness and composition of communities, but also how their structure and function will be modified in the face of global change. [ABSTRACT FROM AUTHOR]

Considering both within- and between-species functional diversities in plant communities has been recently suggested as a way to understand potential assembly mechanisms that control species coexistence. In particular, relating variations in species richness to within- and between-species functional diversities can provide a useful framework for evaluating the importance of alternative community assembly theories. In addition, little is known about whether the relationship between species richness and functional diversity components arises from direct or indirect effects of the abiotic environment., We tested the relationship between functional diversity and species richness by disentangling functional diversity components into within-species, between-species and total functional diversities and by considering potential direct and indirect effects of the abiotic conditions. Multi- and single-trait approaches were applied using three key plant functional traits (height, specific leaf area ( SLA), LDMC). Traits were measured on species coexisting across sixteen species-rich limestone grasslands. Direct and indirect effects of the abiotic conditions were evaluated using multiple soil properties including heterogeneity in soil depths., The within-species functional diversity ranged between 13.5% and 33.6% of the total functional diversity. Within-species diversity was the main functional component linked to variations in species richness, despite the within-species functional diversity being lower than between-species functional diversity. Environmental soil properties had a direct effect on species richness but did not affect functional diversity components., Synthesis: Our results provide evidence that increasing the trait overlap between species, due to an increase in within-species diversity, may relate to greater species coexistence. Disentangling multiple functional diversity components indicated that there may be equalizing mechanisms that act as potential drivers of species coexistence. In addition, it suggests the possibility that this approach may provide a better understanding of the processes involved in the structure of plant communities. [ABSTRACT FROM AUTHOR]

The author comments on the research "Wave-induced changes in seaweed toughness entail plastic modifications in snail traits maintaining consumption efficacy" by M. Molis and others, published within the issue. Topics include effect of wave exposure on the phenotypically plastic trait of seaweed tissue in Fucus vesiculosus, abiotically mediated phenotypic plasticity cascades in other species for abiotic factors, and role of abiotic factors in finding type and strength of community interactions.