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Despite the expected co‐occurrence of effects from resident species, the environment, and disturbance on non‐natives, these factors have largely been treated as acting separately. Co‐occurring factors may, however, act in combination to result in a powerful, yet little explored, mechanism of invasion. Here, we addressed three hypotheses to explain the localized invasion of the non‐native Chenopodium album (Chenopodium) under the canopy of the dominant native tree Neltuma caldenia (Neltuma) in central Argentina. First, we evaluated that Neltuma favors Chenopodium by modifying environmental conditions, and specifically assessed the importance of soil versus that of the microclimate created by Neltuma shade. Second, we tested that Neltuma benefits Chenopodium by promoting under its canopy (calden microsite) the dominance of a grass species, Nassella tenuissima (Nassella), that exerts weaker competitive effects on Chenopodium than those exerted by the dominant grass, Piptochaetium napostaense (Piptochaetium), in adjacent communities free of the tree (open microsite). Lastly, we explored that the invasion of Chenopodium is mediated by disturbance. Chenopodium displayed increased biomass and fecundity (performance) in soil from calden relative to that from open microsites, whereas it exhibited no response to shade treatments. Also, Chenopodium performance in pots with Nassella was similar to that in pots with Piptochaetium. Finally, Chenopodium performance was much greater in pots with no initial plants than in those with grasses. Importantly, in pots without plants, Chenopodium performed much better in calden than open microsites, but in pots with grasses, Chenopodium performance exhibited no differences between microsites. These findings suggest that disturbance mediates Chenopodium invasion in calden microsites. Specifically, disturbance may weaken strong competitive effects from native grasses on Chenopodium, allowing this non‐native herb to benefit from favorable soil conditions under Neltuma. The combined action of natives enhancing resource levels and disturbance providing access to them could be a general mechanism of invasion. [ABSTRACT FROM AUTHOR]

Dormancy allows organisms to survive hostile conditions and is hypothesized to enable species to coexist in fluctuating environments. Although determining how species avoid extinction is critical to understanding the dynamics of natural populations, experimental work exploring if and when dormancy rescues populations from extinction remains rare. We conducted an experiment, where we grew two species of nematode at three temperatures. Strains of Caenorhabditis elegans had mutations altering their propensity to enter a dormant stage and Caenorhabditis briggsae was a single strain with a wildtype background. We used those empirical results to parameterize a model and simulate competitive outcomes in fluctuating environments between the two species. We show that upregulating the dormancy pathway rescues populations that would otherwise go extinct, thereby increasing coexistence between competing species. By leveraging the genetic tools available from a model system, this study provides experimental confirmation that dormancy specifically facilitates species coexistence and thereby promotes diversity. This study system could be used more expansively to explore the role of dormancy in species interactions. [ABSTRACT FROM AUTHOR]

Shrubs are usually adapted to stressful environments in which soil resources are limited, and thus, roots are fundamental for their biological success. However, root measures are challenging to collect, especially in field conditions and at the individual level. For this study, we collected data on the three‐dimensional distribution of fine root biomass of twenty‐three individuals belonging to three shrub species in a mediterranean shrubland in central Spain: gum rockrose Cistus ladanifer, rosemary Salvia rosmarinus, and hairy‐fruited broom Cytisus striatus. Our goal was to determine the soil‐foraging strategies adopted by the plants. We hypothesized that plants would show stabilizing niche differences explaining the high plant biodiversity characteristic of mediterranean shrublands and that they would follow the game theory model's prediction of exploitative segregation of roots behaving territorially but also over‐proliferating roots close to their stem and engaging in a root tragedy of the commons. We found that two‐thirds to three‐fourths of the biomass was belowground, and the system's productivity was roughly 500–600 g C m−2 year−1. Only rosemary plants competed with neighbors following the exploitative segregation predictions. Broom plants had the shallowest and most widespread root systems but significantly reduced their root range toward competing neighbors. Gum rockrose presented deep, narrow root systems avoiding extensive overlap with neighbors but did not appear to respond to competitive pressure levels. Shrubs appeared to stratify their roots at different soil depths, supporting the niche segregation hypothesis. [ABSTRACT FROM AUTHOR]

Simultaneous exposure to multiple stressors complicates the challenge of predicting ecological responses to global environmental change. Here, we show that the contributions of individual species and functional groups to the overall stability of ecosystems can be modified by the presence of different stressors, both individually and in combination. By disturbing natural rocky shore communities with nutrients and sediments and simulating extinction of predatory whelks and grazers, we also found that consumers can simultaneously stabilise and destabilise communities along different stability dimensions, irrespective of their trophic position. Our results suggest that our experimental disturbances influenced consumer contributions to stability indirectly by modifying the interactions between consumers and macroalgae in different ways. These findings merit further exploration in different systems exposed to a range of different stressors to better understand how perturbations of different kinds can modify the multifaceted contributions of species to the overall stability of ecosystems. [ABSTRACT FROM AUTHOR]

Species interactions are influenced by changes to the environment, such as seasonal variations in temperature, and human‐driven warming including marine heatwaves (MHWs). Alteration of species interactions, particularly those involving foundation species, can shape ecosystem structure, stability and dynamics. Marine habitats, notably seagrass meadows, are threatened by human‐driven environmental changes including MHWs which have the potential to alter trophic interactions through effects on various community members including seagrasses, epiphytic algae, and epiphytic algae grazers. Here we examined the effects of a simulated marine heatwave (control versus + 4°C) in different seasons and grazer occurrence on seagrass traits, epiphytic algae growth, grazer biomass and grazing rate. We found the season in which the MHW occurred affected the seagrass response and grazer influence. In winter, the MHW had positive effects on seagrass growth and nitrogen content and caused significant decreases in epiphytic algae growth. However, in summer, grazer presence increased seagrass growth and biomass, but growth was reduced by the interaction with the MHW. The season in which the MHW occurred affected the magnitude of change in leaf tissue isotopic values and C:N ratio, with greater changes occurring in summer. Epiphytic algal growth was markedly reduced by the interaction between all three factors, leading to the near lack of epiphyte growth in summer with grazers present under the MHW. Summer was also associated with a greater increase in snail biomass (most notably under MHW conditions), and increased snail grazing rate. From these results, we show that winter MHWs can drive increased growth of seagrasses but minimal impacts on grazers, while in summer increased grazer activity can interact with elevated temperatures from a MHW to increase their algal consumption. By examining responses across multiple trophic levels and distinct seasons, we achieve a more representative and realistic depiction of human‐induced environmental impacts on ecosystems. [ABSTRACT FROM AUTHOR]

Most animal pollination results from plant–insect interactions, but how we perceive these interactions may differ with the sampling method adopted. The two most common methods are observations of visits by pollinators to plants and observations of pollen loads carried by insects. Each method could favour the detection of different species and interactions, and pollen load observations typically reveal more interactions per individual insect than visit observations. Moreover, while observations concern plant and insect individuals, networks are frequently analysed at the level of species. Although networks constructed using visitation and pollen‐load data have occasionally been compared in relatively specialised, bee‐dominated systems, it is not known how sampling methodology will affect our perception of how species (and individuals within species) interact in a more generalist system. Here we use a Diptera‐dominated high‐Arctic plant–insect community to explore how sampling approach shapes several measures of species' interactions (focusing on specialisation), and what we can learn about how the interactions of individuals relate to those of species. We found that species degrees, interaction strengths, and species motif roles were significantly correlated across the two method‐specific versions of the network. However, absolute differences in degrees and motif roles were greater than could be explained by the greater number of interactions per individual provided by the pollen‐load data. Thus, despite the correlations between species roles in networks built using visitation and pollen‐load data, we infer that these two perspectives yield fundamentally different summaries of the ways species fit into their communities. Further, individuals' roles generally predicted the species' overall role, but high variability among individuals means that species' roles cannot be used to predict those of particular individuals. These findings emphasize the importance of adopting a dual perspective on bipartite networks, as based on the different information inherent in insect visits and pollen loads. [ABSTRACT FROM AUTHOR]

Color polymorphism is an adaptive strategy in which a species exhibits multiple color phenotypes in a population. Often, phenotypes are variably suited to different environmental conditions which may buffer the population against variable conditions. Modern climate change is creating novel selective pressures for many species, especially in winter habitats. Few studies have quantified the benefits of polymorphism for allowing species to cope with climate‐induced environmental change, particularly for species with more cryptic differences between morphs. We investigated how color polymorphism mediates selective pressures in ruffed grouse Bonasa umbellus, a winter‐adapted bird species of North American forests. Ruffed grouse display phenotypic variation in plumage color, ranging from red to gray. Over five winters (2015–2022), we monitored weather conditions, habitat use, and weekly survival for 94 grouse to test whether individuals had lower survival when phenotypically mismatched with snow cover (e.g. a gray bird on a snowless landscape or a red bird in snow). Grouse phenotypically mismatched with snow cover had lower survival, but only when winter survival rates were lowest. During winters of lower overall survival, red grouse exhibited higher survival during snow‐free periods, whereas gray grouse had higher survival when snow was present. We also found that open habitat negatively impacted survival, regardless of color. While the effect of phenotypic mismatch was variable among years, it was a stronger predictor of survival than land cover, suggesting that snow is an important habitat feature mediating overwinter survival. Our work offers an advancement in understanding how environmental variability affects geographic variation in and maintenance of multiple color phenotypes in seasonally‐snow covered environments. Our finding that interactions between color morph and snow cover are important for conferring winter survival provides further evidence that color polymorphism may serve as a buffer against rapidly changing conditions and a pathway for persistence of polymorphic species. Keywords: Bonasa umbellus, color polymorphism, phenotypic mismatch, ruffed grouse, winter ecology, Wisconsin [ABSTRACT FROM AUTHOR]

Species around the globe are shifting their ranges into new territories at an unprecedented rate. In particular, the spread of foundation species can transform recipient communities and ecosystems, however, the effects on belowground processes and diversity remain poorly documented. Belowground fungi are well suited for taking the 'pulse' of changing ecosystems given their rapid turnover and implication in a wide variety of ecosystem processes. To better understand the belowground effects of range‐expanding species, we leveraged an ongoing invasion of a foundation tree species Pinus contorta into alpine tundra to study the impacts on belowground abiotic conditions and the fungal communities associating with the roots of resident plants. We found that individual range‐expanding trees create distinct abiotic 'islands' with wetter soils and altered soil nutrients compared to the surrounding alpine tundra ecosystem. Potentially driven by these abiotic changes, we observed a decrease in the α diversity of mutualistic fungi and an increase in the α‐diversity of pathogenic fungi during later stages of range expansion. Changes in γ‐diversity mirrored patterns of α diversity while β‐diversity was only minorly affected by range‐expanding trees, suggesting that local habitat amelioration/deterioration rather than changes in among‐patch heterogeneity underpin trends in belowground diversity. In sum, our results show that range‐expanding foundation species can modify ecosystems by altering belowground abiotic conditions and diversity across scales. These impacts begin only a few years after initial range‐expansion and establishment and scale rapidly over time, indicating the need for preventative or swift conservation action to prevent long‐term consequences. [ABSTRACT FROM AUTHOR]

Ants often interact aggressively for resources (e.g. nest sites and food) with members of their own or another species. In these competitive interactions, dominant ant species exert a strong influence on ant species coexistence and plant‐associated arthropod community structure. However, few studies have experimentally manipulated the relative abundance of dominant ant species on plants, preventing a mechanistic understanding of the effects of ant competitive interactions on ant community structure as well as on their interactions with other insects, particularly mutualistic hemipterans. In this study, we performed a field experiment in a tropical dry forest in Brazil to investigate the effects of two dominant ant species (Camponotus crassus and Cephalotes pusillus) on the structure ant communities and the abundance of the ant‐tended hemipteran Enchenopa brasiliensis in Solanum lycocarpum plants. For this, we identified and quantified all ant species foraging on plants and estimated the number of egg masses, nymphs and adults of the mutualistic hemipteran before and after experimentally removing nests of both two dominant ant species. Our results showed that removal of C. pusillus nests significantly changed ant community structure, whereas removal of C. crassus nests did not. We also found that nest removal of both dominant ant species had significant effects on hemipteran abundance. In particular, plants generally hosted more hemipteran eggs, nymphs and adults after (vs before) nest removal of both dominant ant species. Overall, this study demonstrates that dominant ant species can play a pivotal role in structuring ant communities and the interactions between ants and honeydew‐producing hemipteran insects. [ABSTRACT FROM AUTHOR]

Anthropogenic stressors are causing widespread coral mortality, leading to loss of coral cover and decreased structural complexity that threatens reef biodiversity, functioning, and ecosystem services. Reef fishes are intimately linked to coral reef complexity, but we lack a generic understanding of which species are particularly affected by reef flattening and what traits make them susceptible. We used extensive species‐ and trait‐based analyses to build a framework for western Atlantic fish association with both structural complexity and coral cover to better understand the implications of reef degradation. These analyses also highlighted the relative importance of live coral versus the structure it provides to reef fishes, which currently remains unclear. We modeled how 25 biophysical and anthropogenic factors correlated with the densities of 109 fish species across 3292 Floridian reef sites. The importance of a metric of structural complexity and coral cover to the abundance of each species was then isolated. Species with positive associations were categorized as likely future 'losers' and negative associations as 'winners'. We predicted that 53% of species will be losers on low‐relief reefs, while only 11% were losers with decreased coral cover. We found morphological, behavioral, and ecological traits, not phylogeny, mediate species' responses to reef degradation and that the loss of structure seemed more critical than the loss of coral cover. Eight traits explained 79.7% of the variation in species' associations with relief and six traits explained 27.8% of associations with coral cover. Smaller, streamlined, habitat and trophic generalists are more likely winners on flattened reefs and large‐bodied predators, among other taxa, are likely losers of reef flattening. Identifying these important traits provides insight into mechanisms that may link fish and complex habitats, which allows us to better predict assemblage‐wide responses to future reef flattening. [ABSTRACT FROM AUTHOR]

Weed species are ecological models that recently received considerable attention due to their particular strategies linked to their ruderal‐competitive traits. They are known to have the potential to provide additional floral resources for insects in flower‐poor agroecosystems. However, their floral traits are much more scarcely studied than those of plants found in other habitats, such as grasslands. The aim of this study was to describe the floral phenotype of weeds and to determine to what extent their floral traits match their ecological strategies as described based on leaf traits. We cultivated 19 forb weeds from perennial agroecosystems, previously identified in Mediterranean fields, in a greenhouse for seven months and collected data on 12 floral and five leaf traits. We tested whether these traits covaried and exhibited an ecological strategy at the phenotype scale. We found that in matters of flower production, weed species face a tradeoff: either numerous small, low‐stature flowers with small quantities of pollen and nectar, or few, large, higher‐held flowers with more pollen and nectar. The floral traits were found to reflect Grime's CSR strategies: the weed species producing fewer but costlier flowers belonged to C‐strategy species, whereas those producing more but less costly flowers belonged to species dominated by an R strategy. These findings indicate that the potential of weeds as floral resources for insects is related to their ecological strategies, which are known to be affected by agricultural practices that filter species composition. This implies that, as for the provision of other ecosystem services, weed communities can be managed to select species with floral traits matching the requirements of flower‐visiting insects like pollinators or parasitoid wasps. [ABSTRACT FROM AUTHOR]

Predators can directly affect prey populations both through predation (consumption of prey) and risk‐induced trait responses (RITRs) that reduce predation risk but are often associated with a fitness cost. Thousands of studies make clear that RITRs (also termed anti‐predator or defensive traits) including changes in behavior, morphology, and life history, are employed by numerous taxa across diverse ecological systems, and there is large variation in their magnitude. A natural goal is to elucidate the species and circumstances for which and to what magnitude RITRs are expected. A candidate hypothesis is that prey species that experience higher mortality from a predator will exhibit a higher RITR. This hypothesis is an intuitive extension of the fact that invulnerable animals are not expected to exhibit an RITR, while vulnerable species are. We present an example that clarifies why this relationship is not always expected and when it is expected. Other factors may influence the level of the RITR leading to the possibility that a positive relationship is not expected. We elucidate this problem using a mesocosm experiment with a fish–cladoceran system in which there is large variability in the predation rate on different cladoceran species. Results not only did not show a positive relationship, but rather a negative trend between predation rate and the RITR. In fact, highly preyed upon taxa did not respond, while the least preyed upon taxa had the largest responses. These results clarify how the level of predation risk interacts with many factors to determine the RITR of prey. [ABSTRACT FROM AUTHOR]

Plant‐available silicon (Si) concentrations vary considerably across tropical soils, yet the ecological importance of that variation remains largely unresolved. Increased Si availability can enhance growth and modulate foliar nutrient status in many crop species suggesting similar effects might occur in natural systems. However, how growth, foliar Si and macronutrient concentrations as well as their stoichiometry respond to plant‐available Si and how these responses differ across tropical tree species is unknown. We experimentally exposed seedlings of 12 tropical tree species to a gradient of plant‐available Si concentrations, representing 85 % of the variation found across central Panama, and assessed responses in aboveground growth and foliar nutrient status. Furthermore, we assessed whether higher plant‐available Si increases P availability. Increasing plant‐available Si led to increased foliar Si concentrations (by up to 140%). It also led to higher aboveground growth (by up to 220%), and it affected foliar C and N concentrations, and nutrient stoichiometry across species. However, at the species‐level only a small subset of two to four species showed significant growth and foliar nutrient responses. At the soil‐level, plant‐available P remained unchanged along the experimental soil Si gradient. Our results showed that Si can improve growth and/or modulate foliar nutrient status in a number of tropical tree species. Furthermore, species' growth and foliar nutrient concentrations might vary differently across tropical forest sites varying in plant‐available Si. Additionally, Si‐induced responses in foliar nutrient stoichiometry have the potential to affect herbivory and litter decomposition. Taken together, natural variation in plant‐available Si might influence plant performance unequally across tropical tree species, and change trophic interactions, with potential implications for ecosystem processes. [ABSTRACT FROM AUTHOR]

Living roots and their rhizodeposits can accelerate or decelerate the decomposition of soil organic matter which refers to the rhizosphere priming effect (RPE). However, whereas plant traits are thought to be key factors controlling the RPE, little is known about how root traits representative of plant biomass allocation, morphology, architecture, or physiology influence the magnitude of the RPE. Using a natural abundance 13C tracer method allowing partitioning of native soil organic carbon (SOC) decomposition and plant rhizosphere respiration, we studied here the effects of eight C3 tree species featuring contrasting functional traits on C4 soil respiration over a 204‐day period in a microcosm experiment. All tree species enhanced the rate of SOC decomposition, by 82% on average, but the strength of the rhizosphere priming significantly differed among species. Mean diameter of first‐order roots and root exudate‐derived respiration were positively correlated with the RPE, together explaining a large part of observed variation in the RPE (R2 = 0.72), whereas root branching density was negatively associated with the RPE. Path analyses further suggested that mean diameter of first‐order roots was the main driver of the RPE owing to its positive direct effect on the RPE and its indirect effects via root exudate‐derived respiration and root branching density. Our study demonstrates that the magnitude of the RPE is regulated by complementary aspects of root morphology, architecture and physiology, implying that comprehensive approaches are needed to reveal the multiple mechanisms driving plant effects on the RPE. Overall, our results emphasize the relevance of integrating root traits in biogeochemical cycling models to improve model performance for predicting soil C dynamics. [ABSTRACT FROM AUTHOR]

Nitrogen (N) deposition is a primary driver of species loss in plant communities globally. However, the mechanisms by which high N availability causes species loss remain unclear. Many hypotheses for species loss with increasing N availability highlight density‐dependent mechanisms, i.e. changes in species interactions. However, an alternative set of hypotheses highlights density‐independent detrimental effects of nitrogen (e.g. N toxicity). We tested the role of density‐dependent and density‐independent mechanisms in reducing species performance. For this aim, we used 120 experimental plant communities (mesocosms) comprised of annual species growing together in containers under four fertilization treatments: 1) no nutrient addition (control), 2) all nutrients except N (P, K, and micronutrients), 3) low N (3 gN m−2) + other nutrients, and 4) high N (15 gN m−2) + other nutrients. Each fertilization treatment included two sowing densities to differentiate between the effects of competition (N × density interactions) and other detrimental effects of N. We focused on three performance attributes: the probability of reaching the reproduction period, biomass growth, and population growth. We found that individual biomass and population growth rates decreased with increasing sowing density in all nutrient treatments, implying that species interactions were predominantly negative. The common grass Avena barbata had a higher biomass and population growth under N enrichment, regardless of sowing density. In contrast, the legume Trifolium purpureum showed a density‐independent reduction in biomass growth with increasing N. Lastly, the small forb Silene palaestina showed a density‐dependent reduction in population growth, i.e. the decline occurred only under high density. Our results demonstrate that density‐dependent and density‐independent mechanisms operate simultaneously to reduce species performance under high N availability. Yet, their relative importance varies among species and life stages. [ABSTRACT FROM AUTHOR]

Climate change is altering the multifunctionality of ecosystems worldwide and is often associated with changes in biodiversity that can modulate the impacts of climate change on ecosystems through interactive effects. Genetic and phenotypic variation within species are particularly influenced by climatic conditions, and can mediate several ecosystem processes. Here, we tested whether temperature can interact with intraspecific variation to drive ecosystem multifunctionality. Using a common gardening experiment, we test the consequences of intraspecific variation (population identity and trait variation) of a consumer fish species (European minnow Phoxinus phoxinus) and temperature on ecosystem multifunctionality, as well as on the biomass of a subsequent fish generation (long‐term effects). We found that individuals from different populations affect ecosystem multifunctionality independently of temperature, and that multifunctionality differed between cold and warm mesocosms. Moreover, when investigating sub‐components of multifunctionality, we found a positive relationship between individual metabolic rate and multifunctional primary production in warm mesocosms, whereas this relationship was reversed in cold mesocosms. We similarly found evidence that the long‐term effect of intraspecific trait variation on the biomass of the next fish generation was temperature‐dependent. These findings demonstrate that differences among populations can have strong consequences on ecosystem multifunctionality, and that intraspecific variation must be considered in addition to other components of global change to predict the impacts of global change on ecosystem multifunctionality. [ABSTRACT FROM AUTHOR]

Quantifying the cumulative effects of stressors on individuals and populations can inform the development of effective management and conservation strategies. We developed a Bayesian state–space model to assess the effects of multiple stressors on individual survival and reproduction. In the model, stressor effects on vital rates are mediated by changes in underlying health, allowing for the comparison of effect sizes while accounting for intrinsic factors that might affect an individual's vulnerability and resilience. We applied the model to a 50‐year dataset of sightings, calving events and stressor exposure of critically endangered North Atlantic right whales Eubalaena glacialis. The viability of this population is threatened by a complex set of stressors, including vessel strikes, entanglement in fishing gear and fluctuating prey availability. We estimated that blunt and deep vessel strike injuries and severe entanglement injuries had the largest effect on the health of exposed individuals, reinforcing the urgent need for mitigation measures. Prey abundance had a smaller but protracted effect on health across individuals, and estimated long‐term trends in survival and reproduction followed the trend of the prey index, highlighting that long‐term ecosystem‐based management strategies are also required. Our approach can be applied to quantify the effects of multiple stressors on any long‐lived species where suitable indicators of health and long‐term monitoring data are available. [ABSTRACT FROM AUTHOR]

Placing traits into novel evolutionary contexts may profoundly alter their functional roles. Here, we investigated whether the elaiosome, a lipid‐rich appendage located on seeds, retained its role as a seed dispersal trait promoting mutualisms with insectivorous ants following human‐mediated introduction of the elaiosome‐bearing Carduus nutans into the Argentinean Caldenal. This system is located within the Neotropical region, an alleged myrmecochory cold spot. Specifically, we first tested the assumption that the elaiosome mediates the interaction between C. nutans and the native ant Pheidole bergi. Then, we explored the hypothesis that, instead of a mutualism, the elaiosome promotes an antagonism between these species because P. bergi predates on both insects and seeds. Finally, we assessed the possibility that the elaiosome is rare in our system, as predicted from its location within the Neotropics. By manipulating the presence/absence of C. nutans' elaiosomes, we demonstrated that P. bergi strongly prefers to collect seeds with versus without C. nutans' elaiosomes, indicating that the elaiosome indeed mediates the interaction between these species. While we detected no direct signs of predation on nor alteration of viability in seeds recovered from P. bergi's refuse dumps, 80% of offered C. nutans seeds remained inside P. bergi colonies, where they are likely consumed by ants, buried too deep for emergence or destroyed by pathogens. Importantly, by quantifying the outcome of the C. nutans–P. bergi interaction, we showed that this relationship is strongly antagonistic. Finally, by sampling taxa most likely to have elaiosomes, we identified eight native species with that trait, preliminary confirming that elaiosome‐bearing species are uncommon in the Caldenal. Taken together, our findings suggest that the elaiosome promotes an antagonism that deters invasion in a cold spot of myrmecochore diversity. The functions of phenotypic traits can thus vary according to the ecological and evolutionary contexts in which they operate. [ABSTRACT FROM AUTHOR]

Globally, ecosystems are experiencing dramatic alterations in the supply of resources, including nutrients. How the temporal regime (press versus pulse), independent of total resource supply, affects growth and species interactions of primary producers remains unexplored. Coral reefs experience anthropogenic modifications to nutrient regimes, making it critical to understand impacts on primary producers, such as macroalgae. In mesocosms, we examined how three macroalgae respond to temporal pattern in nutrient regime (ambient, press, pulse) and species interactions (alone, pairwise, or all together) in terms of their individual growth and assemblage productivity. We found nutrient regime and species interactions influenced individual growth and total assemblage productivity. Press regimes promoted the highest productivity of total assemblages. We observed species interactions ranging from competitive to facilitative varied between macroalgal species and nutrient regimes. Ours is the first study to demonstrate the temporal regime of nutrient delivery, independent of total nutrient supply, strongly impacts the productivity of species assemblages, the nature and outcome of species interactions, and the relative growth rates of individual producer species. As nutrient regimes increasingly fluctuate for coastal marine ecosystems in the Anthropocene, our findings imply macroalgal community composition may also fluctuate. More broadly, our study highlights the importance of assessing primary producer species' responses to varying nutrient regimes to understand factors structuring their communities. [ABSTRACT FROM AUTHOR]

Facilitation is an interaction where one species (the benefactor) positively impacts another (the beneficiary). However, the reciprocal effects of beneficiaries on their benefactors are typically only documented using short‐term datasets. We use Azorella selago, a cushion plant species and benefactor, and a co‐occurring grass species, Agrostis magellanica, on sub‐Antarctic Marion Island, comparing cushion plants and the grasses growing on them over a 13‐year period using a correlative approach. We additionally compare the feedback effect of A. magellanica on A. selago identified using our long‐term dataset with data collected from a single time period. We hypothesized that A. selago size and vitality would be negatively affected by A. magellanica cover and that the effect of A. magellanica on A. selago would become more negative with increasing beneficiary cover and abiotic‐severity, due to, e.g. more intense competition for resources. We additionally hypothesized that A. magellanica cover would increase more on cushion plants with greater dead stem cover, since dead stems do not inhibit grass colonization or growth. The relationship between A. magellanica cover and A. selago size and vitality was not significant in the long‐term dataset, and the feedback effect of A. magellanica on A. selago did not vary significantly with altitude or aspect; however, data from a single time period did not consistently identify this same lack of correlation. Moreover, A. selago dead stem cover was not significantly related to an increase in A. magellanica cover over the long term; however, we observed contrasting results from short‐term datasets. Long‐term datasets may, therefore, be more robust (and practical) for assessing beneficiary feedback effects than conventional approaches, particularly when benefactors are slow‐growing. For the first time using a long‐term dataset, we show a lack of physical cost to a benefactor species in a facilitative interaction, in contrast to the majority of short‐term studies. [ABSTRACT FROM AUTHOR]

Habitat loss is a global threat to biodiversity with pervasive effects on species and populations. These impacts may generate cascading effects on ecological processes propagating across ecological networks. Thus, understanding how habitat loss affects ecological networks is fundamental for conservation. We used a database of 25 plant–frugivore networks distributed across the whole Brazilian Atlantic Forest to understand how landscape‐scale habitat loss shapes network structure, robustness, species role and traits related to seed dispersal. We compared whether these network properties have linear or non‐linear relationships and used centrality metrics and indirect effects to evaluate if habitat loss change the role of species in plant–frugivore networks. We found linear and non‐linear relationships with negative effects of habitat loss on the network structure. As a consequence of shifts in species richness and number of links, the number of interactions and the proportion of possible interactions observed (connectance) were negatively associated with habitat loss. In contrast, nestedness increased with habitat loss. Network robustness, mean bill width and mean seed size were not significantly related to habitat loss. In addition to changes in interaction patterns at network level, habitat loss also favors changes in interaction among species, shifting the species playing central roles in network organization or contributing to indirect effects in the networks. In forested landscapes, obligate frugivores are the main central species in the network, and the ones potentially contributing to indirect effects, while in deforested landscapes these roles are fulfilled by occasional frugivores. Thus, our results emphasize the widespread effect of habitat loss on plant–frugivore systems, adding evidence that its pervasive effects on biodiversity also proliferate on mutualistic interactions with negative consequences for seed dispersal that potentially go beyond the direct pairs of interacting species. [ABSTRACT FROM AUTHOR]

The socio–spatial organization of populations of territorial species refers to the way distance, variation in social status and variation in resource availability interact to shape the way territory‐bounded individuals are distributed. I investigated the resulting reproductive skew, i.e. the emergence of a few high performers amidst a majority of mediocre performers, using lifetime reproductive success data from 46 species living in contrasting landscape configurations. I applied three skew statistics that captured different aspects of the individual heterogeneity: the skewness, the Gini coefficient of inequalities and Hill's index of heavy‐tailed distribution. I also used a simplistic theoretical model, in which only immediate neighbors interacted. In the comparative analysis, the distribution of lifetime reproductive success was more skewed but also more egalitarian in homogeneous than heterogeneous landscapes, after controlling for the allometric effect of the body mass. The simulations indicated that a possible explanatory mechanism for the change in egalitarian properties is that some individuals hide behind their neighbors in the socio‐spatial organization. They therefore secure a better territory than if the distribution was despotic. The ideal despotic model without spatial restriction on interactions could not explain the correlations. This work emphasizes that the shape of the distribution of fitness components conveys information besides the mean and the variance, and the potential for nontrivial effects to emerge from simple movement heuristics. [ABSTRACT FROM AUTHOR]

Warming, the most prominent aspect of global environmental change, already affects most ecosystems on Earth. In recent years, biologists have increasingly integrated the effects of warming into their models by capturing how temperature shapes their physiology, ecology, behavior, evolutionary adaptation and probability of extirpation/extinction. The more physiologically‐grounded approaches to predicting ectotherms' responses use thermal performance curves (TPCs) obtained by measuring species performance (e.g. growth rate) under different temperatures. TPCs are typically measured while other factors are held constant at benign levels to 'isolate' the effects of temperature. Here we highlight that this practice paints a misleading picture because TPCs are functions of other factors, including global change stressors. We review evidence that resource limitation, pH, oxygen and CO2 concentration, salinity, water availability, parasites and mutualists, all influence TPC shape and thermal traits such as optimum temperature for growth. Evidence from a wide variety of organisms – phytoplankton, protists, plants, insects and fish – points towards such interactions increasing organisms' susceptibility to high temperatures (reducing it in the case of mutualists). Failing to account for these interactions is likely to lead to erroneous predictions of performance in nature and an underestimation of the risks of warming. We discuss the general patterns and possible consequences of such interactions for ecological communities. But importantly, interactions with TPCs share common features that we can learn from. Incorporating these interactions into population and community models should lead to deeper insights and more accurate predictions of species' performance in nature – as well as strategies for managing natural and agricultural ecosystems in the face of warming. [ABSTRACT FROM AUTHOR]

Nutrient acquisition in plants can be represented by a suite of intercorrelated root traits such as root diameter, nitrogen content, root tissue density and specific root length. However, it is unclear how a plant's ability to precisely forage for nutrients in a heterogeneous soil environment (i.e. the precision of placing roots into nutrient‐rich areas) relates to these traits. Mycorrhizal symbiosis also affects the relationship between the fine root traits and root foraging precision because fungal hyphae may be used for foraging instead of roots. Hypotheses matching high root foraging precision with low mycorrhizal colonization or 'fast' acquisitive strategies of plants have been raised based either on data from tree species or a limited number of herbaceous species. To test these hypotheses, we compiled data quantifying the experimentally measured degree to which root biomass responded to patchy substrate nutrient concentrations (i.e. root foraging precision) for 123 herbaceous grassland species using a partial meta‐analysis. We tested root foraging precision relationship with root traits involved in nutrient acquisition and mycorrhizal symbiosis (root diameter, specific root length, root tissue density, root tissue nitrogen content and mycorrhizal colonization). The root foraging precision data came from four different pot experiments, and the trait data were extracted from publicly available trait databases. We used a phylogenetically informed approach in order to detect the degree of conservation of the relationships. We found that root foraging precision was not significantly correlated with other fine root traits and mycorrhizal colonization. Thus, it appears unrelated to the main dimensions of the nutrient acquisition space of herbaceous species, namely acquisitive–conservative strategy and outsourcing of acquisition to the fungi. Also, we found only a very weak phylogenetic signal in root foraging precision of 123 species. Our results suggest that root foraging precision constitutes another distinct, evolutionarily independent dimension in herbaceous species' trait space. [ABSTRACT FROM AUTHOR]

Hierarchical compound topologies of interaction networks that are segmented into internally nested modules have received scant attention, compared to simple nested and modular topologies. This is due to the lack of a theoretical model that encompasses all relevant alternative topologies, and an effective method to differentiate compound from simple topologies. Here we present a framework to address compound topologies in ecological networks. We propose a mechanistic schema of processes that generate modular, nested and compound topologies, based on differences in availability and preferences among species. We show that, in combination, these processes produce a unique signature in the structure of compound topologies. Then, we propose a procedure to identify this signature and hence discriminate among simple and compound topologies. We test the efficiency of this procedure in a set of synthetic matrices and then apply it to an actual plant–herbivore network (Asteraceae and their flowehead feeders in Brazil). In this case, the compound topology is clearly substantiated, demonstrating that these advances are applicable to empirical ecological networks and that compound patterns decidedly belong to the array of topologies to be probed in interaction assemblages at various scales. By including extramodular structures in the analysis of compound topologies, we enhance our understanding of how community‐wide networks are organized and their responses to various drivers. [ABSTRACT FROM AUTHOR]

Predator control remains one of the most common strategies for the conservation of threatened prey species. Despite significant and ongoing efforts to reduce predator populations, little is known about the impacts on the behaviour and interactions of target and non‐target species following numerical and potentially behavioural suppression of predators. We used camera‐trap data collected before and after an intensive wolf control program in northeastern Alberta's boreal forest to evaluate changes in activity patterns and overlap in wolves, competitors and prey. We hypothesized wolves would shift their activity toward increased nocturnality to avoid diurnal control efforts, and thereby cause a behavioural cascade where other species shift activity to maintain temporal segregation from wolves. Wolves shifted activity into the nighttime following predator control, reducing temporal overlap with the other, mostly diurnal, members of the community. Decreases in activity overlap between wolves and other species indicates reduced potential for wolf interactions with ungulate prey and large competitor species. Predator control may therefore not only release species from top to down regulation and competition following numerical suppression of top predators, but also through de‐coupling of temporal overlap, with potential effects on species interactions. Understanding the indirect impacts of conservation strategies such as predator control on both target and non‐target species provides insight into potential disruptions to top–down regulation and the associated species interactions that shape community structure. [ABSTRACT FROM AUTHOR]

By transferring energy and nutrients from plankton to top predators, forage species play a major ecological role in marine food webs. While large differences in energy densities have been demonstrated among these species, other determinants of their quality remain poorly explored. We analysed 78 forage species from the Bay of Biscay, NE Atlantic, for their concentrations in various chemical elements with a documented biological role (i.e. micro‐nutrients). Species encompassed jellyfish, crustaceans, cephalopods, cartilaginous and bony fish. Elements included two essential macro‐minerals (nitrogen and phosphorous) and nine trace elements (arsenic (As), cobalt, copper (Cu), chromium, iron, manganese, nickel, selenium (Se), zinc). We showed a broad range of elemental composition values across forage species, partly driven by taxonomy (fish versus crustaceans/cephalopods) or their habitat (coastal versus oceanic, pelagic versus benthic). Some elements (As, Cu or Se) were more variable than others, especially in fish for Cu and Se. The 78 forage species were then classified by hierarchical clustering analysis (HCA) into different nutritional groups, based on their composition in eleven elements. Mean concentrations of each element in the diet of eight cetacean species was finally calculated, as well as the importance of each nutritional group (as defined by HCA including all elements) for each predator species. We revealed contrasting diets in terms of exposure to elements. Neritic common dolphins and harbour porpoises but also minke whales were thus mainly supplied by the Se‐enriched nutritional group composed of small (pelagic) schooling fish (including sandeels, (horse) mackerel and also some Clupeids), while the diets of pilot whales or Risso's dolphins that mostly consume benthic cephalopods were clearly Cu‐enriched. This study raises the issue of essential element composition as another determinant of food quality, and the risk associated with changes in forage species' availability for the proper functioning of marine food webs and ecosystems. [ABSTRACT FROM AUTHOR]

Plant diversity has often been reported to decrease insect herbivory in plants. Of the numerous mechanisms that have been proposed to explain this phenomenon, how plant diversity influences plant defences via effects on growth has received little attention. In addition, plant diversity effects may be contingent on abiotic conditions (e.g. resource and water availability). Here, we used a long‐term experiment to explore the interactive effects of tree species composition and water availability on growth, direct (i.e. phenolics) and indirect (i.e. volatile organic compounds – VOCs) defences and leaf herbivory in Quercus ilex. We quantified herbivory by chewing insects, phenolic compounds and VOCs in Q. ilex trees growing in stands differing in tree species composition (Q. ilex, Q. ilex + Betula Pendula, Q. ilex + Pinus pinaster and Q. ilex + B. pendula + P. pinaster) and water availability (irrigated versus control). Both direct and indirect defences were affected by tree species composition, but such changes were not mediated by changes in tree stem diameter. Quercus ilex trees growing in stands with P. pinaster had the lowest concentration of both direct and indirect defences. Importantly, the effects of tree species composition on VOCs were exacerbated on irrigated blocks. Despite variation in defences, tree species composition did not affect herbivory in Q. ilex. Accordingly, we did not find any association between defences and insect herbivory. Our results suggest that changes in the micro‐environment rather than growth‐defence associations may mediate tree diversity effects on defences. In addition, reduced defensive investment in more diverse stands could negatively impact tree resistance masking the beneficial effects of species diversity at reducing insect herbivory. [ABSTRACT FROM AUTHOR]

Climate change has strong effects on biodiversity. It causes shifts in the species' geographical range, towards other latitudes or elevations, while tracking its natural habitat. Here, the species maintains its realised niche stable (in the environmental space) and shifts its geographical range. Alternatively, a species might shift its realised niche through its fundamental niche, maintaining its geographical range stable, when tracking its natural habitat is not possible. Following this last hypothesis, we aimed to assess changes in species' environmental conditions based on their historical distribution. Within the environmental space, we compared the climatic realised niche of 300 species of several groups of flora and fauna between 1979 and 2013 in the Iberian Peninsula with ecospat R package, under the assumption of no distribution shift over time. We used the same species' distribution data in both periods. We used CHELSA yearly averaged time‐series data for 1979 and 2013. We analysed the differences in the climate between 1979 and 2013 with a Kruskal–Wallis test, by subtracting each pair of variables, and by subtracting the first three components of a PCA. For each species, we measured the realised niche similarity with Schoener's D index, the realised niche overlap with the stability, unfilling and expansion indices, and the distance between realised niche centroids. The climate between 1979 and 2013 changed in the Iberian Peninsula: climate variability reduces in 2013. Most of the species do not have equivalent realised niches. Although very few species had completely dissimilar niches, many species have shifted their realised niches to some degree. In only 35 years, it was already possible to observe how the realised niches of some species started to shift. [ABSTRACT FROM AUTHOR]

Decreased and increased intrinsic growth rate and abundance of a single species can severely and negatively impact other species in the same food web. Here we compare the wider system effects of decreased and increased intrinsic growth rates of species occupying different trophic levels. Specifically, we derive the change in growth rate of a single (focal) species necessary to cause a 90% reduction in the abundance – a quasi‐extinction – of another species in model communities. We find that even relatively small changes, negative as well as positive, in the growth rate of the focal species can cause quasi‐extinctions of others. Furthermore, the magnitude of change needed to cause a quasi‐extinction depends on the trophic level of the perturbed species. The potential ecosystem impact of such 'negative' and 'positive' changes is largely unknown. We argue that such a targeted decrease or increase could be induced by human interference, such as hunting or harvesting, but also by an outbreak or fade‐out of an infectious disease. As ecosystems maintain many and diverse infectious agents, these results suggest that these agents may play an important role in the structure and balance of ecosystems. [ABSTRACT FROM AUTHOR]

Floral traits often display sexual dimorphism in insect‐pollinated dioecious plant species, with male individuals typically being showier than females. While this strategy is theorized to be optimal when pollinators are abundant, it might represent a risk when they become scarce, because the disproportionately high number of visits on the most attractive sex, males, might preclude efficient pollen transfer from males to females. Here, the effect of sexual dimorphism on pollination efficiency was assessed in experimental arrays of dioecious Silene dioica that were exposed to one frequent visitor of the species, Bombus terrestris, and that differed in the magnitude of sexual dimorphism for either flower number or flower size. We found that flower number dimorphism negatively affected the number of visits on female plants, on female flowers and on the number of female flowers visited after a male flower. However, flower number dimorphism had no effect on the number of pollen grains deposited per stigma, presumably because the decrease in the number of visits to female flowers was compensated by a higher number of pollen grains deposited per visit. Flower size dimorphism did not affect visitation patterns and pollen transfer in our experimental arrays. These results highlight the need to jointly study visitation patterns and pollen receipt on stigmas when exploring the effect on floral phenotypes on pollination efficiency. [ABSTRACT FROM AUTHOR]

The impact of global change on biodiversity is commonly assessed in terms of changes in species distributions, community richness and community composition. Whether and how much associations between species are also changing is much less documented. In this study, we quantify changes in large‐scale patterns of species associations in bird communities in relation to changes in species composition. We use network approaches to build three community‐aggregated indices reflecting complementary aspects of species association networks. We characterise the spatio–temporal dynamics of these indices using a large‐scale and high‐resolution dataset of bird co‐abundances of 109 species monitored for 17 years (2001–2017) from 1969 sites across France. We finally test whether spatial and temporal changes in species association networks are related to species homogenisation estimated as the spatio–temporal dynamics of species turnover (β‐diversity) and community generalism (community generalisation index). The consistency of these relationships is tested across three main habitats, namely woodland, grassland and human settlements. We document a directional change in association‐based indices in response to modifications in species turnover and community generalism in space and time. Weaker associations and sparser networks were related to lower spatial species turnover and higher community generalism, suggesting an overlooked aspect of biotic homogenisation affecting species associations and may also have an impact on species interactions. We report that this overall pattern is not constant across habitats, with opposite relationships between biotic homogenisation and change in species association networks in urban versus forest communities suggesting distinct homogenisation processes. Although species associations contain only partial signatures of species interactions, our study highlights that biotic homogenisation translates to finer changes in community structure by affecting the number, strength and type of species associations. [ABSTRACT FROM AUTHOR]

Understanding the causes of the generally positive relationship between biodiversity and ecosystem function (BEF) is a major research focus in ecology. Early analyses of BEF used a modification of the evolutionary Price equation to partition effects of biodiversity into components of complementarity (species richness) and dominance (species composition). However, early experiments and data on BEF did not use information on species traits or relative abundances. Here we extend the Price partition of the total expression of a single trait (such as leaf area) between two communities into five additive components: 1) species richness; 2) average species trait expression; 3) relative abundance; 4) the combined effects of relative abundance and trait expression; 5) absolute abundance. When applied to presence–absence data with no trait variation, the method yields a result that is identical to the original Price partition into two components of complementarity and dominance. When applied to an analysis of relative abundance itself as a trait, our method quantifies the strength of species co‐occurrences as a difference in Simpson diversity between the communities. We tested the new partition with artificial data sets and null model comparisons, and applied it to a long‐term data set on plant succession. A key finding is that the effects of total abundance might be very important when comparing two communities, and possibly could account for results from previous studies in which complementarity emerged as an important contributor to BEF. [ABSTRACT FROM AUTHOR]

Herbivory is a core ecosystem function that is delivered heterogeneously across space. Disentangling the drivers of foraging patterns is key to understanding the functional impact of herbivores. Because intrinsic drivers of foraging like metabolism, nutritional requirements and movement costs scale allometrically, foraging movement patterns in terrestrial herbivores have been shown to also scale positively with body size. However, spatial patterns of herbivory can also be explained by orthogonal factors such as trophic position, competition and functional groupings. Here, we investigate body size and species traits as drivers of the spatial scaling of foraging patterns in herbivorous coral reef fishes. We quantified foraging patterns of 119 individuals from nine common herbivorous species using focal individual surveys. Body size, species identity, feeding substrata, social grouping and functional group were tested as predictors of three foraging metrics: foraging area, inter‐foray distance and tortuosity. Our resulting model revealed that species identity overshadowed body size as a predictor in models for all foraging metrics. While foraging area was explained best by species only, the resulting tortuosity and mean inter‐foray distance models included a small effect of body size that explained within‐species variation. We do not find strong support for size‐scaling of foraging patterns in our study species. These findings indicate that foraging allometry based on Optimal foraging theory cannot be generally applied to reef fish assemblages due to a diversity of foraging strategies, such as spatial partitioning and territoriality. Our work reveals the importance of behavioural ecology and taxonomic diversity in understanding herbivory, especially given the functional differences across species. With coral reefs under threat across the world, this is an important step to disentangling the spatial delivery of a core ecosystem function. [ABSTRACT FROM AUTHOR]

Modern coexistence theory (MCT) holds the potential to study the ability of species to avoid extinction (i.e. to persist) across community types but is rarely applied beyond pairs of competing species. Here, we show that this limitation can be overcome by mapping species according to their niche () and fitness differences (). This application provides three main benefits to study processes of multispecies persistence across trophic levels. First, mapping introduces a novel categorization of species and communities according to the high‐level processes at play: frequency dependence (negative or positive), the occurrence of positive species interactions (facilitation and mutualism) and whether persistence is possible without the presence of other species because of trophic interactions, such as herbivory or predation. Therefore, this mapping can be seen as a toolbox to describe how species persistence depends on species interactions. Second, mapping facilitates studying how species persistence responds to environmental changes that shift intrinsic growth rates and the strength and sign of species interactions. Third, mapping has the potential to foster synthesis across community types because it can accommodate co‐occurrence of positive, negative and neutral interactions between species. We, therefore, argue that mapping can promote collaboration across sub‐fields, as it provides a common concept to link disparate ecological communities. [ABSTRACT FROM AUTHOR]

Overexploitation of natural resources is often viewed as a problem characteristic of only the human species. However, any species could evolve a capacity to overexploit its essential resources through natural selection and competition, even to the point of resource collapse. Here, we describe the processes that potentially lead to overexploitation and synthesize what is known about overexploitation limiters in other species. We propose that there are five pathways that counteract the evolutionary drive towards overexploitation and/or mitigate its consequences: top–down trophic control, interference, cost‐efficiency tradeoffs, resource trait evolution, and spatial heterogeneity. These mechanisms constrain the number of exploiters and/or lower the rate of the resource usage at the individual level. We hypothesize that in ecosystems with reasonable functional diversity, coevolution strengthens this limiter network, preventing overexploitation, and thus argue that diversity begets stability via evolution. Violent population cycles in species‐poor northern ecosystems and eruptions of invading alien species are exceptions that confirm this rule, because these ecosystems either lack functional diversity or there has not been enough time for coevolution to play out its stabilizing role. We propose that the overexploitation by our own species could be prevented via a network of socio‐economical limiters that act in an analogous way. [ABSTRACT FROM AUTHOR]

Phenotypic evolution in sympatric species can be strongly impacted by species interactions, either mutualistic or antagonistic. Heterospecific reproductive behaviours between sympatric species have been shown to favour phenotypic divergence of traits used as sexual cues. Those traits may also be involved in local adaptation or in other types of species interactions and, as a result, undergo complex evolutions across sympatric species. Here we focus on mimicry and study how reproductive interference may impair phenotypic convergence between species with various levels of defence. We use a deterministic model assuming two sympatric species where individuals can display two different warning colour patterns. This eco‐evolutionary model explores how ecological interactions shape phenotypic evolution within sympatric species. We investigate the effect of 1) the opposing density‐dependent selections exerted on colour patterns by predation and reproductive behaviour and 2) the impact of relative species and phenotype abundances on the fitness costs faced by each individual depending on their species and phenotype. Our model shows that reproductive interference may limit the convergent effect of mimetic interactions and may promote phenotypic divergence between Müllerian mimics. The divergent and convergent evolution of traits also strongly depends on the relative species and phenotype abundances and levels of trophic competition, highlighting how the eco‐evolutionary feedbacks between phenotypic evolution and species abundances may result in strikingly different evolutionary routes. [ABSTRACT FROM AUTHOR]

Understanding the relative contribution of different biotic interactions in shaping species assemblages constitutes a major goal in community ecology, and consequently, multiple methods aimed at inferring the nature of these associations have emerged during the last decade. In this framework, the stress‐gradient hypothesis (SGH) predicts that prevalent biotic interactions shift from competition to facilitation as abiotic stress increases (and productivity decreases). This hypothesis originally raised by plant ecologists has been barely applied to faunal communities. Here, we take advantage of 20 years of abundance data to investigate pairwise patterns in species co‐occurrence in alpine bird communities inhabiting two contrasting habitat types: forests (high productivity) and mountain grasslands (low productivity). We also integrate functional data with presence–absence and quantitative matrices in order to detect the signature of processes driving community assembly and test for limiting similarity. We employ a null model approach, probabilistic pairwise association tests and joint species distribution models; all methods revealed a higher frequency of positive interactions in mountain grasslands in agreement with SGH predictions. Both the frequency of positive and negative interactions remained moderately stable over the study period in both habitat types. There was no significant relationship between the degree of co‐occurrence of species pairs and their functional distance in either habitat. However, when we only considered those combinations of species whose co‐occurrence patterns deviated from that expected at random, we found that co‐existing species are functionally more similar than those pairs that show segregated patterns in the forest assemblages. Such a relationship may arise via selective social information use and other processes, including microhabitat preferences. Overall, our findings suggest that interspecific competition does not constitute a major force driving the structure of bird assemblages in this mountain region. This work also shows that association analyses should not be underestimated as they can provide clues to the mechanisms responsible for community structure. [ABSTRACT FROM AUTHOR]

The relationship between niche and distribution, and especially the role of biotic interactions in shaping species' geographic distributions, has gained increasing interest in the last two decades. Most ecological research has focused on negative species interactions, especially competition, predation and parasitism. Yet the relevance of positive interactions – mutualisms and commensalisms – have been brought to the fore in recent years by an increasing number of empirical studies exploring their impact on range limits. Based on a review of 73 studies from a Web of Science search, we found strong evidence that positive interactions can influence the extent of species' geographic or ecological ranges through a diversity of mechanisms. More specifically, we found that while obligate interactions, and especially obligate mutualisms, tend to constrain the ranges of one or both partners, facultative positive interactions tend to widen ranges. Nonetheless, there was more variation in effects of facultative interactions on range limits, pointing to important context‐dependencies. Therefore, we propose that conceptual development in this field will come from studying ecological interactions in the context of networks of many species across environmental gradients, since pairwise interactions alone might overlook the indirect and environmentally‐contingent effects that species have on each other in communities of many interacting species. Finally, our study also revealed key data gaps that limit our current understanding of the pervasiveness of effects that positive interactions have on species' ranges, highlighting potential avenues for future theoretical and experimental work. [ABSTRACT FROM AUTHOR]

Protection mutualists display territorial behaviors, which also act as protective services for their host species. These territorial behaviors may inhibit the ability of other organisms to use the habitat provided by the host species. Coral guard crabs (Trapeziidae) and snapping shrimps (Alpheidae) form a guild of protection mutualists that aggressively defend their obligate host corals from predators. Here, we investigate how these protection mutualists affect the colonization and/or establishment of the community associated with the host coral. We found that Trapezia intermedia and Alpheus lottini both had species‐specific effects on the probability of colonization. Alpheus lottini inhibited recruitment by conspecifics, but did not affect the settlement of Trapezia spp. T. intermedia did not affect recruitment by Trapezia spp. or Alpheus spp. Both T. intermedia and A. lottini limited colonization by some other decapod species, including xanthid and portunid crabs. The presence of protection mutualists affected the trajectory of communities associated with host corals such that the initial presence of protection mutualists explained 20% of variation in community composition six‐months later. The communities on corals with protection mutualists had similar richness but lower beta‐diversity than control corals after six months. Host response to protection mutualists was mixed. Over the two‐month colonization study when the mutualist treatments were maintained and colonizing species were removed, host corals with both protection mutualists had lower growth rates than control corals or corals with only T. intermedia; however, coral growth did not differ between treatments over the six‐month establishment study when community trajectories were followed without interference. [ABSTRACT FROM AUTHOR]

Plant ecosystem structure is understood to be a result of complex multitrophic interactions. Most multitrophic studies focus on plant aboveground adaptations to aboveground herbivore pressures, neglecting belowground adaptations in response to aboveground damage. Differential investment in root structures may allow plants to compensate for tissue loss or damage due to herbivores. Furthermore, phylogeny may constrain a plant's ability to adapt belowground. We examined the belowground responses of 12 species of oak Quercus to varying locations and intensities of simulated herbivore damage. We first established that oak belowground traits responded to aboveground herbivory by measuring patterns of investment in coarse versus fine root structures and re‐allocation of non‐structural carbohydrates (NSC) to root storage. We then tested whether phylogeny could explain variations in investment patterns using phylogenetic independent contrasts. Plant adaptations to aboveground herbivory included allocating biomass and carbon reserves to root structures, depending on the location and intensity of herbivore damage. NSC re‐allocation to root storage was observed when oak species experienced any type of damage, but damage to lateral tissues caused a greater re‐allocation than apical damage or control treatments. We found that most belowground responses to aboveground herbivory are species‐specific and may be adapted for environmental conditions or type of herbivory. Some responses to herbivore damage, such as changes in fine‐root mass and root sugar concentrations, were phylogenetically constrained. Phylogenetic constraints generally occur when there is severe damage at the apical meristem. Plants may adapt to aboveground tissue loss due to varying herbivore pressures (i.e. varying location and intensity of damage) by differentially investing in root types and NSC re‐allocation to root storage. Understanding linkages between and phylogenetic constraints of plant belowground responses to aboveground herbivory will improve our understanding of the ecological processes involved in multitrophic interactions. [ABSTRACT FROM AUTHOR]

Communities can be described by species, interactions and the network of interactions which emerge from these building blocks. Networks are often summarized by diverse metrics which capture key components of network topology, for example, number of trophic levels, number of interactions per species (i.e. degree) and frequency of apparent competition modules (i.e. motifs). Network metrics are often used to predict whole community responses following a perturbation. Understanding whether our predictive capabilities at the network level are maintained at other levels of organization such as species and interaction levels is critical but rarely studied. Our objective was to determine whether we can use different network metrics (e.g. modularity, species roles) to predict which networks, species and interactions will persist following a perturbation. Given the nested structure of interactions, species and networks, we hypothesized that those metrics which were correlated with network persistence would be the same metrics correlated with which species and interactions persist and that the direction of these correlations would be maintained across organizational levels (i.e. network, species and interactions). We used numerical simulations of a dynamic food web model and model selection to test the relationships between network metrics (e.g. degree, modularity, motif profiles) and network, species and interaction‐level persistence. We found that out degree and frequency of both apparent and exploitative competition were the best predictors of species persistence, however all metrics were weak predictors of species persistence. This demonstrates that metrics which predict network persistence are not always the best predictors of species and interaction level persistence. Additionally, metrics can work in opposition depending on the organizational scope examined; for example interaction strength is positively correlated with interaction persistence, but negatively correlated with species persistence. Multiscale analysis of network metrics such as this one, may provide critical insight for advancing network‐based environmental management in the Anthropocene. [ABSTRACT FROM AUTHOR]

Competition is assumed to shape niche widths, affecting species survival and coexistence. Expectedly, high interspecific competition will reduce population niche widths, whereas high intraspecific competition will do the opposite. Here we test in situ how intra‐ and interspecific competition affects trophic resource use and the individual and population niche widths of two lacustrine fish species, Arctic charr and brown trout, covering a 40 year study period with highly contrasting competitive impacts prior to and following a large‐scale fish culling experiment. Initially, an overcrowded Arctic charr population dominated the study system, with brown trout being nearly absent. The culling experiment reduced the littoral Arctic charr density by 80%, whereupon brown trout gradually increased its density in the system. Thus, over the study period, the Arctic charr population went from high to low intraspecific competition, followed by increasing interspecific competition with brown trout. As hypothesized, the relaxed intraspecific competition following the experimental culling reduced individual diet specialization and compressed population niche width of Arctic charr. During the initial increase of the brown trout population, there was a large dietary overlap between the two species. Over the subsequent intensified interspecific competition from the population build‐up of brown trout, their trophic niche overlap chiefly declined due to a dietary shift of Arctic charr towards enhanced zooplankton consumption. Contrary to theoretical expectations, the individual and population niche widths of Arctic charr increased with intensified interspecific competition. In contrast, the diet and niche width of brown trout remained stable over time, confirming its competitive superiority. The large‐scale culling experiment and associated long‐term research revealed pronounced temporal dynamics in trophic niche and resource use of the inferior competitor, substantiating that intra‐ and interspecific competition have large and contrasting impacts on individual and population niches. [ABSTRACT FROM AUTHOR]

Ecosystems world‐wide experience changes in species composition in response to natural and anthropogenic changes in environmental conditions. Research to date has greatly improved our understanding of how species affect focal ecosystem functions. However, because measurements of multiple ecosystem functions have not been consistently justified for any given trophic group, it is unclear whether interpretations of research syntheses adequately reflect the contributions of consumers to ecosystems. Using model communities assembled in experimental microcosms, we examined the relationship between four numerically dominant detritivore species and six ecosystem functions that underpin fundamental aspects of carbon and nitrogen cycling above‐ and below‐ground. We tested whether ecosystem responses to changes in detritivore identity depended upon species trait dissimilarity, food web compartment (aboveground, belowground, mixed) or number of responses considered (one to six). We found little influence of detritivore species identity on brown (i.e. soil‐based) processes. Only one of four detritivore species uniquely influenced decomposition, and detritivore species did not vary in their influence on soil nitrogen pools (NO3− and NH4+), or root biomass. However, changes in detritivore identity influenced multiple aboveground ecosystem functions. That is, by serving as prey, ecosystem engineers and occasionally also as herbivores as well as detritivores, these species altered the strength of aboveground predator–herbivore interactions and plant–shoot biomass. Yet, dissimilarity of detritivore functional traits was not associated with dissimilarity of ecosystem functioning. These results serve as an important reminder that consumers influence ecosystem processes via multiple energy channels and that food web interactions set important context for consumer‐mediated effects on multiple ecosystem functions. Given that species are being lost, gained and redistributed at unprecedented rates, we can anticipate that changes in species identity will have additional ecosystem consequences beyond those predicted by species' primary functional role. [ABSTRACT FROM AUTHOR]

Improving our understanding of stability across spatial scales is crucial in the current scenario of biodiversity loss. Still, most empirical studies of stability target small scales. We experimentally removed the local space‐dominant species (macroalgae, barnacles, or mussels) at eight sites spanning more than 1000 km of coastline in north‐ and south‐central Chile, and quantified the relationship between area (the number of aggregated sites) and stability in aggregate community variables (total cover) and taxonomic composition. Resistance, recovery, and invariability increased nonlinearly with area in both functional and compositional domains. Yet, the functioning of larger areas achieved a better, albeit still incomplete, recovery than composition. Compared with controls, smaller disturbed areas tended to overcompensate in terms of total cover. These effects were related to enhanced available space for recruitment (resulting from the removal of the dominant species), and to increasing beta diversity and decaying community‐level spatial synchrony (resulting from increasing area). This study provides experimental evidence for the pivotal role of spatial scale in the ability of ecosystems to resist and recover from chronic disturbances. This knowledge can inform further ecosystem restoration and conservation policies. [ABSTRACT FROM AUTHOR]

It remains unclear how evolutionary and ecological processes have shaped the wide variety of plant life strategies, especially in highly diverse ecosystems like tropical forests. Some evidence suggests that species have diversified across a gradient of ecological strategies, with different plant tissues converging to optimize resource use across environmental gradients. Alternative hypotheses propose that species have diversified following independent selection on different tissues, resulting in a decoupling of trait syndromes across organs. To shed light on the subject, we assembled an unprecedented dataset combining 19 leaf, stem and root traits for 1467 tropical tree species inventoried across 71 0.1‐ha plots spanning broad environmental gradients in French Guiana. Nearly 50% of the overall functional heterogeneity was expressed along four orthogonal dimensions, after accounting for phylogenetic dependences among species. The first dimension related to fine root functioning, while the second and third dimensions depicted two decoupled leaf economics spectra, and the fourth dimension encompassed a wood economics spectrum. Traits involved in orthogonal functional strategies, five leaf traits in particular but also trunk bark thickness, were consistently associated with a same gradient of soil texture and nutrient availability. Root traits did not show any significant association with edaphic variation, possibly because of the prevailing influence of other factors (mycorrhizal symbiosis, phylogenetic constraints). Our study emphasises the existence of multiple functional dimensions that allow tropical tree species to optimize their performance in a given environment, bringing new insights into the debate around the presence of a whole plant economic spectrum in tropical forest tree communities. It also emphasizes the key role that soil heterogeneity plays in shaping tree species assembly. The extent to which different organs are decoupled and respond to environmental gradients may also help to improve our predictions of species distribution changes in responses to habitat modification and environmental changes. [ABSTRACT FROM AUTHOR]

Complex spatial patterns are common in coastal marine systems, but mechanisms underlying their formation are disputed. Most empirical work has focused on exogenous spatially structured disturbances as the leading cause of pattern formation in species assemblages. However, theoretical and observational studies suggest that complex spatial patterns, such as power laws in gap‐size distribution, may result from endogenous self‐organized processes involving local‐scale interactions. The lack of studies simultaneously assessing the influence of spatially variable disturbances and local‐scale interactions has fuelled the idea that exogenous and endogenous processes are mutually exclusive explanations of spatial patterns in marine ecosystems. To assess the relative contribution of endogenous and exogenous processes in the emergence of spatial patterns, an intertidal assemblage of algae was exposed for two years to various combinations of intensity and spatial patterns of disturbance. Localized disturbances impinging at the margins of previously disturbed clearings and homogenous disturbances without any spatial pattern generated heterogeneous distributions of disturbed gaps and macroalgal patches, characterized by a power‐law scaling. Spatially varying disturbances produced a spatial gradient in the distribution of algal patches and, to a lesser extent, also a power‐law scaling in both patch‐ and gap‐size distributions. These results suggest that exogenous and endogenous processes are not mutually exclusive forces that can lead to the formation of similar spatial patterns in species assemblages. [ABSTRACT FROM AUTHOR]

A central theme in ecological research is to understand how species interactions contribute to community dynamics. Species interactions are the basis of parametric (model‐driven) and nonparametric (model‐free) approaches in theoretical and empirical work. However, despite their different interpretations across these approaches, these measures have occasionally been used interchangeably, limiting our opportunity to use their differences to gain new insights about ecological systems. Here, we revisit two of the most used measures across these approaches: species interactions measured as constant direct effects (typically used in parametric approaches) and local aggregated effects (typically used in nonparametric approaches). We show two fundamental properties of species interactions that cannot be revealed without bridging these definitions. First, we show that the local aggregated intraspecific effect summarizes all potential pathways through which one species impacts itself, which are likely to be negative even without any constant direct self‐regulation mechanism. This property has implications for the long‐held debate on how communities can be stabilized when little evidence of self‐regulation has been found among higher‐trophic species. Second, we show that a local aggregated interspecific effect between two species is correlated with the constant direct interspecific effect if and only if the population dynamics do not have any higher‐order direct effects. This other property provides a rigorous methodology to detect direct higher‐order effects in the field and experimental data. Overall, our findings illustrate a practical route to gain further insights about non‐equilibrium ecological dynamics and species interactions. [ABSTRACT FROM AUTHOR]

Modern human societies have negatively impacted native species richness and their adaptive capacity on every continent, in clearly contrasting ways. We propose a general model to explain how the sequence, duration and type of colonising society alter native species richness patterns through changes in evolutionary pressures. These changes cause different 'filtering effects' on native species, while simultaneously altering the capacity of surviving species to adapt to further anthropogenic pressures. This framework may better explain the observed native species extinction rates and extirpation legacies following human colonisation events, as well as better predict future patterns of human impact on biodiversity. [ABSTRACT FROM AUTHOR]

Ecological stoichiometry seeks to understand the ecological consequences of elemental imbalances between consumers and their resources. Therein, the well‐accepted growth rate hypothesis (GRH) states that organisms exhibiting rapid growth have higher phosphorus (P) demand – and thus lower C:P and N:P ratios – than slow growing ones, due to a higher allocation to P‐rich rRNA. However, GRH has rarely been extended to other biological traits than growth, especially at the community level. In this study, we investigated whether macroinvertebrate stoichiometric traits (e.g. C:P and N:P ratios) can be linked to their development traits, and whether these stoichiometric traits are related to macroinvertebrate community assemblage under different nutrient conditions. We allocated more than 400 European taxa to different groups, defined using available information about three development‐related traits: 'life span', 'voltinism' and 'number of reproductive cycles per individual'. We sampled 18 invertebrate taxa in six streams exhibiting different levels of nutrient concentration and measured their stoichiometric traits. Further, we quantified invertebrate taxon abundances in these streams during an annual survey. Based on these data, we tested whether community composition regarding the developmental groups differs, depending on nutrient concentration. We found significant differences in the proportions of the developmental groups along a gradient of water N:P, in relation to their stoichiometric traits. Taxa with low C:P and N:P ratios were generally associated with faster development groups, and these taxa tended to occur at higher proportions in streams exhibiting low dissolved N:P ratios. In contrast, communities from P‐poor, high dissolved N:P streams, were dominated by slowly developing taxa with high N:P ratios. Our results highlight that extending the GRH to species development rate might give some insights about the mechanisms by which nutrient concentrations in ecosystems influence consumers' community composition. [ABSTRACT FROM AUTHOR]