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Background: The efficacy of transcranial direct current stimulation (tDCS) has been studied extensively. The cathodic (c‐tDCS), anodic (a‐tDCS), and bihemispheric stimulation have demonstrated efficacy in the management of the paretic upper extremity (UE) after stroke, but it has not been determined which stimulation polarity has, so far, shown the best results. Objective: To evaluate the available evidence to determine which tDCS polarity has the best results in improving UE motor function after stroke. Methods: PubMed, PEDro, Web of Science, EMBASE, and SCOPUS databases were searched. Different Medical Subject Headings (MeSH) terms were combined for the search strategy, to cover all studies that performed a comparison between different tDCS configurations focused on UE motor rehabilitation in people with lived experience of stroke. Results: Fifteen studies remained for qualitative analysis and 12 for quantitative analysis. Non‐significant differences with a 95% confidence interval (CI) were obtained for c‐tDCS versus a‐tDCS (g = 0.10, 95% CI = −0.13; 0.33, p =.39, N = 292), for a‐tDCS versus bihemispheric (g = 0.02, 95% CI = −0.46; 0.42, p =.93, N = 81), and for c‐tDCS versus bihemispheric (g = 0.09, 95% CI = −0.84;.66, p =.73, N = 100). No significant differences between the subgroups of the meta‐analysis were found. Conclusions: The results of the present meta‐analysis showed no evidence that a stimulation polarity is superior to the others in the rehabilitation of UE motor function after stroke. A non‐significant improvement trend was observed toward c‐tDCS compared to a‐tDCS. [ABSTRACT FROM AUTHOR]

The environmental filtering of species traits can influence the identity of their interaction partners and the contribution of species interactions to ecosystem functioning, but the extent to which this process is influenced by landscape composition and configuration remains unclear. We combined a field experiment with an agent‐based model to assess how landscape structure and local flower patch isolation affect pollinator body‐size distribution and plant–pollinator interactions, sampled at different spatial extents. We then evaluated how these changes in pollinator functional (i.e. body‐size) diversity influence plant reproduction. We observed higher pollinator functional diversity in less‐isolated patches, which promoted plant reproduction via a relationship between functional diversity and interaction complementarity. This complementarity occurred partly because larger pollinators interacted with more plant species. Moreover, we showed that patch configuration at the landscape level can change the direction of these local‐scale patch isolation effects on pollinator body‐size distribution, functional diversity and plant–pollinator interactions. Importantly, these relationships were robust to sampling spatial extent. Thus, management strategies to promote pollination should account for local resources and landscape structure, because response, effect and interaction traits like body size connect landscape filtering effects with local community responses and outcomes of interaction‐based functions. [ABSTRACT FROM AUTHOR]

Switching plant species visited by pollinators (partner flexibility) has been proposed as a behavioural mechanism able to attenuate the negative impacts of shifts in plant communities on pollination. However, it is unclear whether the magnitude of such response is generalizable or depends on the environmental context. Moreover, the ability of pollinators to exploit plants with dissimilar traits (trait flexibility) has been overlooked, even though it can affect the spectrum of new partners available.To shed some light on this problem, we quantified partner and trait flexibility in five communities from four different environments, from Alpine to semi‐arid. We evaluated whether the rate at which pollinators incorporated new plant species throughout the flowering season was similar across communities or context dependent. Then, we assessed whether pollinators changed the type of flowers visited and if such trait flexibility was related to their capacity to visit new plant species. Finally, we developed an agent‐based model to explore whether diet flexibility can protect pollination when the plant community changes. To this end, we used scenarios of phenological decoupling.In general, pollinators switched interaction partners to cope with the temporal replacement of plant species. Yet, the magnitude of such behaviour varied across communities, probably in response to differences in the number of floral resources available. Also, pollinators were able to visit plant species with dissimilar traits, though both components of diet flexibility (partner identity and traits) did not necessarily covary. Thus, to have a full picture of pollinators' diet flexibility, we need to consider the floral traits of partners. Finally, our theoretical model shows that diet flexibility can protect pollination after shifts in plant communities, but that such positive effects are limited by trait‐matching between co‐occurring species.Synthesis. Overall, our study highlights the importance of incorporating plant traits when evaluating the ability of pollinators to find new interaction partners. Besides, our simulation results suggest that diet flexibility may not unequivocally protect pollination against changes in plant communities, especially if they entail shifts in the characteristics of the floral assemblage, and hence, the ability of pollinators to find new interaction partners can be compromised. [ABSTRACT FROM AUTHOR]

Ecological restoration has been increasingly considering biotic interactions. Different restoration strategies usually rely on different composition and abundance of plants with potential impact on the establishment of plant–pollinator interactions. We evaluated the restoration of plant–pollinator interaction networks in young restoration areas in the South Atlantic rainforest, Brazil. We assessed the relative contribution of two restoration strategies (natural regeneration vs. reforestation), geographic distance, plant composition, pollinator composition, abundance of flowers and insects, and plant–pollinator temporal overlap, that is, phenological coupling, to predict the establishment of pairwise interactions. We expected that restoration strategies would indirectly affect the patterns (identity and frequency) of pairwise interactions due to their influence on the processes driving interactions. We sampled monthly pollinators and the plants they visited on six reforestation sites and six natural regeneration sites during 20 months. We surveyed flower abundance in summer. We analyzed the relative contribution of each factor to predict the identity and frequency of pairwise interactions using structural equation modeling. Contrary to expectations, the restoration strategy did not predict interactions, probably because the sites under restoration were surrounded by natural and conserved landscapes. Since we found no effect of restoration strategies on plant composition, abundance, and phenological coupling, the restoration strategy did not predict interactions. Phenological coupling explained more than half of the interaction patterns, representing the best predictor of interactions followed by abundance and plant composition. Therefore, these predictors should be considered to select plant species in restoration projects that encompass interactions and pollination services. [ABSTRACT FROM AUTHOR]

It is not uncommon for one or a few species, and their interactions, to have disproportionate effects on other species in ecological communities. Such keystone interactions might affect how communities respond to the invasion of non‐native species by preventing or inhibiting the establishment, spread or impact of non‐native species.We explore whether a keystone mutualism among a hummingbird–mistletoe–marsupial promotes ecological resistance to an invasive pollinator, the bumblebee Bombus terrestris, by comparing data collected at sites prior to bumblebee invasion to data collected 11 years after the invasion in sites with and without the keystone mutualism.We built pollination networks and focused on network motifs, regarded as building blocks of networks, to identify the central pollinators and estimate the change in their interactions after invasion of B. terrestris. We also estimated the interaction rewiring across the season in post‐invasion networks and tested it as a possible mechanism explaining how the keystone mutualism increased ecological resistance to invasion.We found two times more species in post‐invasion sites with the keystone mutualism than in post‐invasion sites without the keystone mutualism. Moreover, we found that invasive bumblebee reduced the strength and interaction niche of the five central pollinator species while increasing its own strength and interaction niche, suggesting a replacement of interactions. Also, we found that the keystone mutualism promoted resistance to B. terrestris invasion by reducing its negative impacts on central species. In the presence of the keystone mutualism, central species had three times more direct interactions than in sites without this keystone mutualism. The higher interaction rewiring, after invasion of B. terrestris, in sites with the keystone mutualism indicates greater chances of central pollinators to form new interactions and reduces their competence for resources with the non‐native bumblebee.Our results demonstrate that a keystone mutualism can enhance community resistance against the impacts of a non‐native invasive pollinator by increasing species diversity and promoting interaction rewiring in the community. This study suggests that the conservation of mutualisms, especially those considered keystone, could be essential for long‐term preservation of natural communities under current and future impacts of global change. [ABSTRACT FROM AUTHOR]

Understanding the impacts of global change on ecological communities is a major challenge in modern ecology. The gain or loss of particular species and the disruption of key interactions are both consequences and drivers of global change that can lead to the disassembly of ecological networks. We examined whether the disruption of a hummingbird–mistletoe–marsupial mutualism by the invasion of non‐native species can have cascading effects on both pollination and seed dispersal networks in the temperate forest of Patagonia, Argentina. We focused on network motifs, subnetworks composed of a small number of species exhibiting particular patterns of interaction, to examine the structure and diversity of mutualistic networks. We found that the hummingbird–mistletoe–marsupial mutualism plays a critical role in the community by increasing the complexity of pollination and seed dispersal networks through supporting a high diversity of interactions. Moreover, we found that the disruption of this tripartite mutualism by non‐native ungulates resulted in diverse indirect effects that led to less complex pollination and seed dispersal networks. Our results demonstrate that the gains and losses of particular species and the alteration of key interactions can lead to cascading effects in the community through the disassembly of mutualistic networks. [ABSTRACT FROM AUTHOR]

Generalist species are the linchpins of networks, as they are important for maintaining network structure and function. Previous studies have shown that interactions between generalists tend to occur consistently across years and sites. However, the link between temporal and spatial interaction persistence across scales remains unclear. To address this gap, we collected data on plant–pollinator interactions throughout the flowering period for 5 yr across six plots in a subalpine meadow in the Rocky Mountains. We found that interactions between generalists tended to persist more in time and space such that interactions near the network core were more frequently recorded across years, within seasons, and among plots. We posit that species' tolerance of environmental variation across time and space plays a key role in generalization by regulating spatiotemporal overlap with interaction partners. Our results imply a role of spatiotemporal environmental variation in organizing species interactions, marrying niche concepts that emphasize species environmental constraints and their community role. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Most studies of plant–animal mutualistic networks have come from a temporally static perspective. This approach has revealed general patterns in network structure, but limits our ability to understand the ecological and evolutionary processes that shape these networks and to predict the consequences of natural and human‐driven disturbance on species interactions. We review the growing literature on temporal dynamics of plant–animal mutualistic networks including pollination, seed dispersal and ant defence mutualisms. We then discuss potential mechanisms underlying such variation in interactions, ranging from behavioural and physiological processes at the finest temporal scales to ecological and evolutionary processes at the broadest. We find that at the finest temporal scales (days, weeks, months) mutualistic interactions are highly dynamic, with considerable variation in network structure. At intermediate scales (years, decades), networks still exhibit high levels of temporal variation, but such variation appears to influence network properties only weakly. At the broadest temporal scales (many decades, centuries and beyond), continued shifts in interactions appear to reshape network structure, leading to dramatic community changes, including loss of species and function. Our review highlights the importance of considering the temporal dimension for understanding the ecology and evolution of complex webs of mutualistic interactions. [ABSTRACT FROM AUTHOR]

Studying how habitat loss affects the tolerance of ecological networks to species extinction (i.e. their robustness) is key for our understanding of the influence of human activities on natural ecosystems. With networks typically occurring as local interaction networks interconnected in space (a meta‐network), we may ask how the loss of specific habitat fragments affects the overall robustness of the meta‐network. To address this question, for an empirical meta‐network of plants, herbivores and natural enemies we simulated the removal of habitat fragments in increasing and decreasing order of area, age and connectivity for plant extinction and the secondary extinction of herbivores, natural enemies and their interactions. Meta‐network robustness was characterized as the area under the curve of remnant species or interactions at the end of a fragment removal sequence. To pinpoint the effects of fragment area, age and connectivity, respectively, we compared the observed robustness for each removal scenario against that of a random sequence. The meta‐network was more robust to the loss of old (i.e. long‐fragmented), large, connected fragments than of young (i.e. recently fragmented), small, isolated fragments. Thus, young, small, isolated fragments may be particularly important to the conservation of species and interactions, while contrary to our expectations larger, more connected fragments contribute little to meta‐network robustness. Our findings highlight the importance of young, small, isolated fragments as sources of species and interactions unique to the regional level. These effects may largely result from an unpaid extinction debt, whereby younger fragments are likely to lose species over time. Yet, there may also be more long‐lasting effects from cultivated lands (e.g. water, fertilizers and restricted cattle grazing) and network complexity in small, isolated fragments. Such fragments may sustain important biological diversity in fragmented landscapes, but maintaining their conservation value may depend on adequate restoration strategies. [ABSTRACT FROM AUTHOR]

The study of mutualistic interaction networks has led to valuable insights into ecological and evolutionary processes. However, our understanding of network structure may depend upon the temporal scale at which we sample and analyze network data. To date, we lack a comprehensive assessment of the temporal scale‐dependence of network structure across a wide range of temporal scales and geographic locations. If network structure is temporally scale‐dependent, networks constructed over different temporal scales may provide very different perspectives on the structure and composition of species interactions. Furthermore, it remains unclear how various factors – including species richness, species turnover, link rewiring and sampling effort – act in concert to shape network structure across different temporal scales. To address these issues, we used a large database of temporally‐resolved plant–pollinator networks to investigate how temporal aggregation from the scale of one day to multiple years influences network structure. In addition, we used structural equation modeling to explore the direct and indirect effects of temporal scale, species richness, species turnover, link rewiring and sampling effort on network structural properties. We find that plant–pollinator network structure is strongly temporally‐scale dependent. This general pattern arises because the temporal scale determines the degree to which temporal dynamics (i.e. phenological turnover of species and links) are included in the network, in addition to how much sampling effort is put into constructing the network. Ultimately, the temporal scale‐dependence of our plant–pollinator networks appears to be mostly driven by species richness, which increases with sampling effort, and species turnover, which increases with temporal extent. In other words, after accounting for variation in species richness, network structure is increasingly shaped by its underlying temporal dynamics. Our results suggest that considering multiple temporal scales may be necessary to fully appreciate the causes and consequences of interaction network structure. [ABSTRACT FROM AUTHOR]

Niche and neutral processes jointly influence species interactions. Predictions of interactions based on these processes assume that they operate similarly across all species. However, species characteristics could systematically create differences in the strength of niche or neutral processes for each interspecific interaction.We used national‐level records of plant–frugivore interactions, species traits, biogeographic status (native vs. exotic), phylogenies and species range sizes to test the hypothesis that the strength of niche processes in species interactions changes in predictable ways depending on trophic generalism and biogeographic status of the interacting species.The strength of niche processes (measured as trait matching) decreased when the generalism of the interacting partners increased. Furthermore, the slope of this negative relationship between trait matching and generalism of the interacting partners was steeper (more negative) for interactions between exotic species than those between native species. These results remained significant after accounting for the potential effects of neutral processes (estimated by species range size).These observed changes in the strength of niche processes in generating species interactions, after accounting for effects of neutral processes, could improve predictions of ecological networks from species trait data. Specifically, due to their shorter co‐evolutionary history, exotic species tend to interact with native species even when lower trait matching occurs than in interactions among native species. Likewise, interactions between generalist bird species and generalist plant species should be expected to occur despite low trait matching between species, whereas interactions between specialist species involve higher trait matching. [ABSTRACT FROM AUTHOR]

Morphology and phenology influence plant–pollinator network structure, but whether they generate more stable pairwise interactions with higher pollination success remains unknown. Here we evaluate the importance of morphological trait matching, phenological overlap and specialisation for the spatio‐temporal stability (measured as variability) of plant–pollinator interactions and for pollination success, while controlling for species' abundance. To this end, we combined a 6‐year plant–pollinator interaction dataset, with information on species traits, phenologies, specialisation, abundance and pollination success, into structural equation models. Interactions among abundant plants and pollinators with well‐matched traits and phenologies formed the stable and functional backbone of the pollination network, whereas poorly matched interactions were variable in time and had lower pollination success. We conclude that phenological overlap could be more useful for predicting changes in species interactions than species abundances, and that non‐random extinction of species with well‐matched traits could decrease the stability of interactions within communities and reduce their functioning. [ABSTRACT FROM AUTHOR]

Mutualistic networks are highly dynamic, characterized by high temporal turnover of species and interactions. Yet, we have a limited understanding of how the internal structure of these networks and the roles species play in them vary through time.We used 6 years of observation data and a novel statistical method (dynamic stochastic block models) to assess how network structure and species' structural position within the network change throughout subseasons of the flowering season and across years in a quantitative plant–pollinator network from a dryland ecosystem in Argentina.Our analyses revealed a core–periphery structure persistent through subseasons and years. Yet, species structural position as core or peripheral was highly dynamic: virtually all species that were at the core in some subseasons were also peripheral in other subseasons, while many other species always remained peripheral.Our results illuminate our understanding of the dynamics of mutualistic networks and have important implications for ecosystem management and conservation. [ABSTRACT FROM AUTHOR]

Different modelling approaches have been used to relate the structure of mutualistic interactions with the stability of communities. However, inconsistencies arise when we compare modelling outcomes with the patterns of interactions observed in empirical studies. To shed light on these inconsistencies, we explored the network structure–stability relationship by incorporating the cost of mutualistic interactions, a long ignored feature of mutualisms, into population dynamics models. We assessed the changes in the relationship between network structure (species richness, connectance, modularity) and community stability (species persistence, resilience), and between network structure and community structural attributes (average abundance), using models with increasing levels of cost for mutualistic communities. We found that adding the potential cost of mutualistic interactions affected the strength of the network structure–stability relationship. Our results revive the question of whether the structure of mutualistic networks determines community stability. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mutualistic interactions are at the core of community dynamics, determining dispersal, colonization and differential survival and reproduction among individuals and species. Mutualistic interactions therefore affect the fitness of interaction partners, hence modifying their respective evolutionary trajectories reciprocally, potentially leading to coevolution. Although mathematical models predict coevolution in mutualistic interaction networks, no empirical data are available. By taking into account the patterns of interactions and reconstructing evolutionary change in plant and pollinator traits, we tested the hypothesis that coevolution occurs between plants and insects that interact more frequently, or more symmetrically. To test this hypothesis, we built an interaction network with data from five flowering seasons, measured plant and insect morphology, mapped morphology on the plant and insect phylogenies, and reconstructed ancestral character changes based on maximum parsimony. We calculated an index, called the coevolutionary ratio, which represents the amount of correlated change in traits that mediate the interaction between plants and pollinators (i.e. proboscis versus corolla length, and body width and corolla aperture). Our results suggest that high frequency of interaction, i.e. the number of times two species interact, does not lead to coevolution. Instead, symmetry of interaction strength, i.e. the reciprocal similarity in the mutual effect of interaction partners, may lead to coevolution, in spite of a pervasive lack of reciprocal specialization and high interaction frequency. Although the statistical signal is quite weak, our results hold for three statistical tests of very different nature. The most specialized species, expected to be under directional selection, do not show more evolutionary change than do generalist species, expected to be under different, perhaps opposing, selective pressures. By dissecting the complexity of an interaction network we show that coevolution may partially shape functional morphology of interaction partners, thus providing the closest evidence to date of mutualistic adaptation of organisms within a community. [ABSTRACT FROM AUTHOR]

Abstract: Land‐use change is known to affect biodiversity, and there is increasing concern regarding how these changes may impact the provision of ecosystem services. Although functional composition (diversity and identity) could influence ecosystem properties and services at the community level, there is little quantitative understanding of these relationships in the field. Here, we evaluate the direct and indirect effects (through ecosystem properties) of biodiversity on the provision of multiple ecosystem services in native mixed forest in north‐west Patagonia, and how land‐use intensity influences these relationships. We used structural equation modelling to test hypotheses regarding the relationship between understorey plant functional composition, two ecosystem properties, four ecosystem services and silvopastoral use intensity (SUI). We also evaluated two alternative models to assess the mechanism behind biodiversity and ecosystem properties relationships (biomass ratio and niche complementarity). Finally, we performed pairwise correlations to identify synergies and trade‐offs between ecosystem services. SUI affected functional composition, and the provision of three out of four ecosystem services was indirectly affected by land‐use intensity through changes in ecosystem properties. We found that this indirect effect of biodiversity on ecosystem services happens mainly through changes in functional identity rather than functional diversity. Under increasing land‐use intensity, functional composition changed towards a community characterized by a resource acquisition strategy. Trade‐offs between ecosystem services (provisioning vs. regulating) were enhanced under high SUI, while synergies where enhanced under low SUI (provisioning vs. cultural). Thus, although the strength of these relationships varied between SUI, its nature (trade‐off or synergy) stayed the same. Our results expand on previous studies by simultaneously considering the effect of land‐use intensification directly on functional composition and on the ecosystem processes underpinning ecosystem services, as well as on the relationship among them. We provide evidence of an indirect effect of land‐use intensification on multiple ecosystem services through biodiversity. Moreover, we found that functional identity is more important than diversity for ecosystem functionality. Land‐use intensification affects biodiversity, and thus, ecosystem properties, but does not change the relationship among ecosystem services. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

Ecological interactions are highly dynamic in time and space. Previous studies of plant-animal mutualistic networks have shown that the occurrence of interactions varies substantially across years. We analyzed interannual variation of a quantitative mutualistic network, in which links are weighted by interaction frequency. The network was sampled over six consecutive years, representing one of the longest time series for a community-wide mutualistic network. We estimated the interannual similarity in interactions and assessed the determinants of their persistence. The occurrence of interactions varied greatly among years, with most interactions seen in only one year (64%) and few (20%) in more than two years. This variation was associated with the frequency and position of interactions relative to the network core, so that the network consisted of a persistent core of frequent interactions and many peripheral, infrequent interactions. Null model analyses suggest that species abundances play a substantial role in generating these patterns. Our study represents an important step in the study of ecological networks, furthering our mechanistic understanding of the ecological processes driving the temporal persistence of interactions. [ABSTRACT FROM AUTHOR]

Fire represents a frequent disturbance in many ecosystems, which can affect plant-pollinator assemblages and hence the services they provide. Furthermore, fire events could affect the architecture of plant-pollinator interaction networks, modifying the structure and function of communities., Some pollinators, such as wood-nesting bees, may be particularly affected by fire events due to damage to the nesting material and its long regeneration time. However, it remains unclear whether fire influences the structure of bee-plant interactions., Here, we used quantitative plant-wood-nesting bee interaction networks sampled across four different post-fire age categories (from freshly-burnt to unburnt sites) in an arid ecosystem to test whether the abundance of wood-nesting bees, the breadth of resource use and the plant-bee community structure change along a post-fire age gradient., We demonstrate that freshly-burnt sites present higher abundances of generalist than specialist wood-nesting bees and that this translates into lower network modularity than that of sites with greater post-fire ages. Bees do not seem to change their feeding behaviour across the post-fire age gradient despite changes in floral resource availability., Despite the effects of fire on plant-bee interaction network structure, these mutualistic networks seem to be able to recover a few years after the fire event. This result suggests that these interactions might be highly resilient to this type of disturbance. [ABSTRACT FROM AUTHOR]

ABSTRACT While average temperature is likely to increase in most locations on Earth, many places will simultaneously experience higher variability in temperature, precipitation, and other climate variables. Although ecologists and evolutionary biologists widely recognize the potential impacts of changes in average climatic conditions, relatively little attention has been paid to the potential impacts of changes in climatic variability and extremes. We review the evidence on the impacts of increased climatic variability and extremes on physiological, ecological and evolutionary processes at multiple levels of biological organization, from individuals to populations and communities. Our review indicates that climatic variability can have profound influences on biological processes at multiple scales of organization. Responses to increased climatic variability and extremes are likely to be complex and cannot always be generalized, although our conceptual and methodological toolboxes allow us to make informed predictions about the likely consequences of such climatic changes. We conclude that climatic variability represents an important component of climate that deserves further attention. [ABSTRACT FROM AUTHOR]

A frequent observation in plant-animal mutualistic networks is that abundant species tend to be more generalised, interacting with a broader range of interaction partners than rare species. Uncovering the causal relationship between abundance and generalisation has been hindered by a chicken-and-egg dilemma: is generalisation a by-product of being abundant, or does high abundance result from generalisation? Here, we analyse a database of plant-pollinator and plant-seed disperser networks, and provide strong evidence that the causal link between abundance and generalisation is uni-directional. Specifically, species appear to be generalists because they are more abundant, but the converse, that is that species become more abundant because they are generalists, is not supported by our analysis. Furthermore, null model analyses suggest that abundant species interact with many other species simply because they are more likely to encounter potential interaction partners. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The strength of species interactions influences strongly the structure and dynamics of ecological systems. Thus, quantifying such strength is crucial to understand how species interactions shape communities and ecosystems. Although the concepts and measurement of interaction strength in food webs have received much attention, there has been comparatively little progress in the context of mutualism. We propose a conceptual scheme for studying the strength of plant-animal mutualistic interactions. We first review the interaction strength concepts developed for food webs, and explore how these concepts have been applied to mutualistic interactions. We then outline and explain a conceptual framework for defining ecological effects in plant-animal mutualisms. We give recommendations for measuring interaction strength from data collected in field studies based on a proposed approach for the assessment of interaction strength in plant-animal mutualisms. This approach is conceptually integrative and methodologically feasible, as it focuses on two key variables usually measured in field studies: the frequency of interactions and the fitness components influenced by the interactions. [ABSTRACT FROM AUTHOR]

Identifying the determinants of biological interactions in mutualistic networks is key to understanding the rules that govern the organization of biodiversity. We used structural equation modeling and dissimilarities in nine ecological variables to investigate community processes underlying the turnover of species and their interaction frequencies (interaction pattern) among highly resolved plant-pollinator networks. Floral and pollinator community composition, i.e., species identities and their abundances, were strong determinants of the microstructure of pairwise interactions among the networks, explaining almost 69% of their variation. Flower and pollinator traits were directly related to interaction patterns, but were partly masked in the model by shared variance with community composition. Time of year and geographic location, floral and pollinator abundances independent of species identity, and relative abundance of exotic flowers had indirect and relatively weak effects on interaction patterns. Our analyses lead to precise predictions about the processes behind the interaction patterns in mutualistic networks. Future understanding of these processes will be aided by studies that evaluate these predictions experimentally at the network level. [ABSTRACT FROM AUTHOR]

Invasive, alien plants and pollinators have varying effects on their interaction partners, ranging from highly beneficial to strongly detrimental. To understand these contrasting impacts, we review the benefits and costs associated with plant-pollinator interactions and enquire as to how the presence of abundant invaders affects the benefit-cost balance. We provide a conceptual framework that predicts that mutualism shifts to antagonism when invaders increase disproportionally in abundance relative to their interaction partners. This outcome is illustrated by an empirical example of a crop in which flower damage and an associated reduction in fruit quality represent interaction costs of intense visitation by invasive bees. More generally, the extremely high density of invasive flower visitors, such as Apis mellifera and Bombus terrestris, might have population- and community-level consequences by hampering reproduction of native plants while promoting reproduction of alien plants. Furthermore, modification of the structure of pollination networks resulting from intense visitation of native plants by superabundant alien flower visitors in highly invaded communities could predict accentuated interaction costs for many native plants. Owing to their high density and the exclusion of native pollinators, invasive bees, originally introduced for honey production and crop pollination, may negatively impact both the native biota and agriculture. [ABSTRACT FROM AUTHOR]

Species community composition is known to alter the network of interactions between two trophic levels, potentially affecting its functioning (e.g. plant pollination success) and the stability of communities. Phylogenies vary in shape with regard to the rate of evolutionary change across a tree (influencing tree balance) and variation in the timing of branching events (affecting the distribution of node ages in trees), both of which may influence the structure of species interaction networks. Because related species are likely to share many of the traits that regulate interactions, the shape of phylogenetic trees may provide some insights into the distribution of traits within communities, and hence the likelihood of interaction among species. However, little attention has been paid to the potential effects of changes in phylogenetic diversity ( PD) on interaction networks., Phylogenetic diversity is influenced by species diversity within a community, but also how distantly-related the constituent species are from one another. Here, we evaluate the relationship between two important measures of phylogenetic diversity (tree shape and age of nodes) and the structure of plant-pollinator interaction networks using empirical and simulated data. Whereas the former allows us to evaluate patterns in real communities, the latter allows us to evaluate more systematically the relationship between tree shape and network structure under three different models of trait evolution., In empirical networks, less balanced plant phylogenies were associated with lower connectance in interaction networks indicating that communities with the descendants of recent radiations are more diverged and specialized in their partnerships. In simulations, tree balance and the distribution of nodes through time were included in the best models for modularity, and the second best models for connectance and nestedness. In models assuming random evolutionary change through time (i.e. Brownian motion), less balanced trees and trees with nodes near the tips exhibited greater modularity, whereas in models with an early burst of radiation followed by relative stasis (i.e. early-burst models) more balanced trees and trees with nodes near roots had greater modularity., Synthesis. Overall, these results suggest that the shape of phylogenies can influence the structure of plant-pollinator interaction networks. However, the mismatch between simulations and empirical data indicate that no simple model of trait evolution mimics that observed in real communities. [ABSTRACT FROM AUTHOR]

The diversity-stability hypothesis posits that species diversity confers redundancy in function, so that richer communities show higher temporal stability in ecosystem processes than poorer communities. The diversity-stability relationship has not been studied in terms of flower production before. A diverse flower community may stabilize the availability of floral resources along the floral season. Considering this type of stability is important because it could promote the stability and persistence of the pollination service. We evaluated 1) the diversity-stability relationship in floral production along a flowering season; 2) the effect of additional factors that could blur the diversity-stability relationship, such as flower abundance, elevation, and the time elapsed since the last fire, a common human disturbance in the study area; and 3) whether the most important plants for pollinators in terms of interspecific interactions contribute differentially to temporal stability. The most diverse communities were more stable in floral resource production along the flowering season. Stability of flower production was also influenced by a positive indirect effect of elevation. The plants that contributed the most to temporal stability were the most abundant and densely connected species, those at the core of the plant-pollinator network. Our study shows that species richness enhances the availability of floral resources for pollinators, providing a strong support for the diversity-stability hypothesis. [ABSTRACT FROM AUTHOR]

How many dimensions (trait-axes) are required to predict whether two species interact? This unanswered question originated with the idea of ecological niches, and yet bears relevance today for understanding what determines network structure. Here, we analyse a set of 200 ecological networks, including food webs, antagonistic and mutualistic networks, and find that the number of dimensions needed to completely explain all interactions is small ( < 10), with model selection favouring less than five. Using 18 high-quality webs including several species traits, we identify which traits contribute the most to explaining network structure. We show that accounting for a few traits dramatically improves our understanding of the structure of ecological networks. Matching traits for resources and consumers, for example, fruit size and bill gape, are the most successful combinations. These results link ecologically important species attributes to large-scale community structure. [ABSTRACT FROM AUTHOR]

Summary 1. The study of plant-pollinator interactions in a network context is receiving increasing attention. This approach has helped to identify several emerging network patterns such as nestedness and modularity. However, most studies are based only on qualitative information, and some ecosystems, such as deserts and tropical forests, are underrepresented in these data sets. 2. We present an exhaustive analysis of the structure of a 4-year plant-pollinator network from the Monte desert in Argentina using qualitative and quantitative tools. We describe the structure of this network and evaluate sampling completeness using asymptotic species richness estimators. Our goal is to assess the extent to which the realized sampling effort allows for an accurate description of species interactions and to estimate the minimum number of additional censuses required to detect 90% of the interactions. We evaluated completeness of detection of the community-wide pollinator fauna, of the pollinator fauna associated with each plant species and of the plant-pollinator interactions. We also evaluated whether sampling completeness was influenced by plant characteristics, such as flower abundance, flower life span, number of interspecific links (degree) and selectiveness in the identity of their flower visitors, as well as sampling effort. 3. We found that this desert plant-pollinator network has a nested structure and that it exhibits modularity and high network-level generalization. 4. In spite of our high sampling effort, and although we sampled 80% of the pollinator fauna, we recorded only 55% of the interactions. Furthermore, although a 64% increase in sampling effort would suffice to detect 90% of the pollinator species, a fivefold increase in sampling effort would be necessary to detect 90% of the interactions. 5. Detection of interactions was incomplete for most plant species, particularly specialists with a long flowering season and high flower abundance, or generalists with short flowering span and scant flowers. Our results suggest that sampling of a network with the same effort for all plant species is inadequate to sample interactions. 6. Sampling the diversity of interactions is labour intensive, and most plant-pollinator networks published to date are likely to be undersampled. Our analysis allowed estimating the completeness of our sampling, the additional effort needed to detect most interactions and the plant traits that influence the detection of their interactions. [ABSTRACT FROM AUTHOR]

Species-energy theory posits that energy availability regulates population sizes, extinction rates and ultimately species richness. This theory has focused mostly on total energy as a measure of energy availability. However, because energy variation can also influence population sizes and extinction rates, species-energy theory should arguably consider simultaneously both total energy and its variation. Using data on species richness of land birds and mammals, we compared the fit of three species-energy models including total energy, energy variation or both combined. We show that the combination of total energy and energy variation has greater predictive power than any of them considered separately. We also evaluate three crucial assumptions of this modified species-energy theory and show that they are supported by available data. These results illuminate the current debate on climate change, given that both average conditions and variability of climatic conditions are likely to change in the future. [ABSTRACT FROM AUTHOR]

Anthropogenic activities usually trigger changes in the population density of plants. Thus, land management practices can influence density-dependent demographic parameters and species interactions. We investigated plant-pollinator interactions and reproduction in Prosopis flexuosa, the largest tree species in the Central Monte desert of Argentina, an important economic and cultural resource for humans and a functionally prominent species. We hypothesized that reproductive output of P. flexuosa would be limited at low densities, and that exclusion of catle grazing would enhance population density and consequently interaction frequency with pollinators and reproductive success. The study was conducted in and around Ñacuñán Biosphere Reserve (Mendoza, Argentina), where cattle grazing has been excluded for over 35 years. Working in five pairs of protected and cattle grazed 1-ha plots, we recorded density of adult trees, pollinator visitation frequency to inflorescences and seeds per inflorescence in focal trees. Adult tree density was higher in protected plots than in cattle grazed plots. Density of reproductive trees was positively correlated with seed production, suggesting positive density dependence for reproduction (Allee effect). Pollinator visitation to inflorescences and seed production was higher in protected plots compared with plots under cattle grazing. Suppression of anthropogenic degradation has resulted in higher adult tree density in protected plots, indirectly higher pollinator visitation to inflorescences and higher reproductive success of trees. Increased frequency of plant-pollinator interactions and tree reproduction suggest success of management practices aimed at protecting P. flexuosa woodlands. [ABSTRACT FROM AUTHOR]

The structure of mutualistic networks is likely to result from the simultaneous influence of neutrality and the constraints imposed by complementarity in species phenotypes, phenologies, spatial distributions, phylogenetic relationships, and sampling artifacts. We develop a conceptual and methodological framework to evaluate the relative contributions of these potential determinants. Applying this approach to the analysis of a plant-pollinator network, we show that information on relative abundance and phenology suffices to predict several aggregate network properties (connectance, nestedness, interaction evenness, and interaction asymmetry). However, such information falls short of predicting the detailed network structure (the frequency of pairwise interactions), leaving a large amount of variation unexplained. Taken together, our results suggest that both relative species abundance and complementarity in spatiotemporal distribution contribute substantially to generate observed network patters, but that this information is by no means sufficient to predict the occurrence and frequency of pairwise interactions. Future studies could use our methodological framework to evaluate the generality of our findings in a representative sample of study systems with contrasting ecological conditions. [ABSTRACT FROM AUTHOR]

Pollinators may be declining globally, a matter of concern because animal pollination is required by most of the world's plant species, including many crop plants. Human land use and the loss of native habitats is thought to be an important driver of decline for wild, native pollinators, yet the findings of published studies on this topic have never been quantitatively synthesized. Here we use meta-analysis to synthesize the literature on how bees, the most important group of pollinators, are affected by human disturbances such as habitat loss, grazing, logging, and agriculture. We obtained 130 effect sizes from 54 published studies recording bee abundance and/or species richness as a function of human disturbance. Both bee abundance and species richness were significantly, negatively affected by disturbance. However, the magnitude of the effects was not large. Furthermore, the only disturbance type showing a significant negative effect, habitat loss and fragmentation, was statistically significant only in systems where very little natural habitat remains. Therefore, it would be premature to draw conclusions about habitat loss having caused global pollinator decline without first assessing the extent to which the existing studies represent the status of global ecosystems. Future pollinator declines seem likely given forecasts of increasing land-use change. [ABSTRACT FROM AUTHOR]

The topology of plant–animal mutualistic networks has the potential to determine the ecological and evolutionary dynamics of interacting species. Many mechanisms have been proposed as explanations of observed network patterns; however, the fact that plant–animal interactions are inherently spatial has so far been ignored. Using a simulation model of frugivorous birds foraging in spatially explicit landscapes we evaluated how plant distribution and the scale of bird movement decisions influenced species interaction probabilities and the resulting network properties. Spatial aggregation and limited animal mobility restricted encounter probabilities, so that the distribution of animal visits per plant deviated strongly from the binomial distribution expected for a well-mixed system. Lack of mixing in turn resulted in a strong decrease in network connectance, a weak decrease in nestedness, stronger interactions, greater strength asymmetry and the unexpected presence/absence of some interactions. Our results suggest that spatial processes may contribute substantially to structure plant–animal mutualistic networks. [ABSTRACT FROM AUTHOR]

Many ecosystem services are delivered by organisms that depend on habitats that are segregated spatially or temporally from the location where services are provided. Management of mobile organisms contributing to ecosystem services requires consideration not only of the local scale where services are delivered, but also the distribution of resources at the landscape scale, and the foraging ranges and dispersal movements of the mobile agents. We develop a conceptual model for exploring how one such mobile-agent-based ecosystem service (MABES), pollination, is affected by land-use change, and then generalize the model to other MABES. The model includes interactions and feedbacks among policies affecting land use, market forces and the biology of the organisms involved. Animal-mediated pollination contributes to the production of goods of value to humans such as crops; it also bolsters reproduction of wild plants on which other services or service-providing organisms depend. About one-third of crop production depends on animal pollinators, while 60–90% of plant species require an animal pollinator. The sensitivity of mobile organisms to ecological factors that operate across spatial scales makes the services provided by a given community of mobile agents highly contextual. Services vary, depending on the spatial and temporal distribution of resources surrounding the site, and on biotic interactions occurring locally, such as competition among pollinators for resources, and among plants for pollinators. The value of the resulting goods or services may feed back via market-based forces to influence land-use policies, which in turn influence land management practices that alter local habitat conditions and landscape structure. Developing conceptual models for MABES aids in identifying knowledge gaps, determining research priorities, and targeting interventions that can be applied in an adaptive management context. [ABSTRACT FROM AUTHOR]

Plants engage in multiple, simultaneous interactions with other species; some (enemies) reduce and others (mutualists) enhance plant performance. Moreover, effects of different species may not be independent of one another; for example, enemies may compete, reducing their negative impact on a plant. The magnitudes of positive and negative effects, as well as the frequency of interactive effects and whether they tend to enhance or depress plant performance, have never been comprehensively assessed across the many published studies on plant-enemy and plant-mutualist interactions. We performed a meta-analysis of experiments in which two enemies, two mutualists, or an enemy and a mutualist were manipulated factorially. Specifically, we performed a factorial meta-analysis using the log response ratio. We found that the magnitude of (negative) enemy effects was greater than that of (positive) mutualist effects in isolation, but in the presence of other species, the two effects were of comparable magnitude. Hence studies evaluating single-species effects of mutualists may underestimate the true effects found in natural settings, where multiple interactions are the norm and indirect effects are possible. Enemies did not on average influence the effects on plant performance of other enemies, nor did mutualists influence the effects of mutualists. However, these averages mask significant and large, but positive or negative, interactions in individual studies. In contrast, mutualists ameliorated the negative effects of enemies in a manner that benefited plants; this overall effect was driven by interactions between pathogens and belowground mutualists (bacteria and mycorrhizal fungi). The high frequency of significant interactive effects suggests a widespread potential for diffuse rather than pairwise coevolutionary interactions between plants and their enemies and mutualists. Pollinators and mycorrhizal fungi enhanced plant performance more than did bacterial mutualists. In the greenhouse (but not the field), pathogens reduced plant performance more than did herbivores, pathogens were more damaging to herbaceous than to woody plants, and herbivores were more damaging to crop than to non-crop plants (suggesting evolutionary change in plants or herbivores following crop domestication). We discuss how observed differences in effect size might be confounded with methodological differences among studies. [ABSTRACT FROM AUTHOR]

1. Marine cleaning mutualisms generally involve small fish or shrimps removing ectoparasites and other material from cooperating ‘client’ fish. We evaluate the role of fish abundance, body size and behaviour as determinants of interactions with cleaning mutualists. 2. Data come from eight reef locations in Brazil, the Caribbean, the Mediterranean and Australia. 3. We conducted a meta-analysis of client–cleaner interactions involving 11 cleaner and 221 client species. 4. There was a strong, positive effect of client abundance on cleaning frequency, but only a weak, negative effect of client body size. These effects were modulated by client trophic group and social behaviour. 5. This study adds to a growing body of evidence suggesting a central role of species abundance in structuring species interactions. [ABSTRACT FROM AUTHOR]

Plant species sharing pollinators may compete through pollination. This type of competition may lead to overdispersed flowering phenologies. However, phenological segregation is difficult to detect in seasonal climates. We compared patterns of phenological overlap in assemblages of ornithophilous plants from three localities of the temperate forest of southern South America with those generated by four different null models. These species were all visited and presumably pollinated by a single species, the hummingbird Sephanoides sephaniodes, which makes this situation ideal to evaluate the role of pollination-mediated competition. For one site, we compiled data on flowering phenologies for three different years. Three models considered the flowering period of the whole assemblage of ornithophilous plants as the phenological window within which flowering phenologies were randomized, but made no further assumptions on how species should be distributed within that temporal frame. The fourth model assigned differential probabilities to different time intervals based on the flowering onset of non-ornithophilous plant species. Observed mean pairwise overlaps for all localities and years were well within the interval defined by the 2.5 and 97.5% percentiles of the randomized distribution of expected mean pairwise overlaps according to models 1–3. However, model 4 showed a consistent trend towards overdispersion of ornihophilous phenologies, which show a shift towards mid- to late-summer flowering. Thus, to the extent that the distribution of flowering of non-ornithophilous species reflects the constraints imposed by a highly seasonal climate, our results provide support to the proposal that pollinator sharing may cause evolutionary displacement or ecological sorting of flowering phenologies. Other factors, such as phylogenetic inertia, could also contribute to explain extant phenological patterns in the highly endemic ornithophilous flora of the temperate forest of southern South America. [ABSTRACT FROM AUTHOR]

Introduced plant populations lose interactions with enemies, mutualists and competitors from their native ranges, and gain interactions with new species, under new abiotic conditions. From a biogeographical perspective, differences in the assemblage of interacting species, as well as in abiotic conditions, may explain the demographic success of the introduced plant populations relative to conspecifics in their native range. Within invaded communities, the new interactions and conditions experienced by the invader may influence both its demographic success and its effects on native biodiversity. Here, we examine indirect effects involving enemies, mutualists and competitors of introduced plants, and effects of abiotic conditions on biotic interactions. We then synthesize ideas building on Darwin's idea that the kinds of new interactions gained by an introduced population will depend on its relatedness to native populations. This yields a heuristic framework to explain how biotic interactions and abiotic conditions influence invader success. We conclude that species introductions generally alter plants’ interactions with enemies, mutualists and competitors, and that there is increasing evidence that these altered interactions jointly influence the success of introduced populations. [ABSTRACT FROM AUTHOR]

We evaluate whether species interaction frequency can be used as a surrogate for the total effect of a species on another. Because interaction frequency is easier to estimate than per-interaction effect, using interaction frequency as a surrogate of total effect could facilitate the large-scale analysis of quantitative patterns of species-rich interaction networks. We show mathematically that the correlation between interaction frequency ( I) and total effect ( T) becomes more strongly positive the greater the variation of I relative to the variation of per-interaction effect ( P) and the greater the correlation between I and P. A meta-analysis using data on I, P and T for animal pollinators and seed dispersers visiting plants shows a generally strong, positive relationship between T and I, in spite of no general relationship between P and I. Thus, frequent animal mutualists usually contribute the most to plant reproduction, regardless of their effectiveness on a per-interaction basis. [ABSTRACT FROM AUTHOR]

1. Recent studies have evaluated the distribution of specialization in species interaction networks. Species abundance patterns have been hypothesized to determine observed topological patterns. We evaluate this hypothesis in the context of host–parasite interaction networks. 2. We used two independent series of data sets, one consisting of data for seven sites describing interactions between freshwater fish and their metazoan parasites and another consisting of data for 25 localities describing interactions between fleas and their mammalian hosts. We evaluated the influence of species abundance patterns on the distribution of specialization in these host–parasite interaction networks with the aid of null models. 3. In parallel with recent studies of plant–animal mutualistic networks, our analyses suggest that host–parasite interactions in these systems are highly asymmetric: specialist parasites tend to interact with hosts with high parasite richness, whereas hosts with low parasite richness tend to interact mainly with generalist parasites. 4. The observed distribution of specialization was predicted by a null model that assumed that species-specific probabilities of being assigned a link during the randomization process were roughly proportional to their relative abundance. Thus, abundant hosts tend to harbour richer parasite faunas, with a high proportion of rare specialists. [ABSTRACT FROM AUTHOR]

Herbivores can affect plants not only directly through browsing and trampling, but also indirectly through other species. For example, herbivores could affect the interaction between plants and their pollinators. Because plant population density may affect plant-pollinator interactions and plant reproductive success, we hypothesized that herbivores could affect pollination and plant reproduction indirectly by modifying plant population density. Unlike previous hypotheses, which concerned individual-level effects on vegetative and reproductive traits, our hypothesis focuses on population-level effects and involves a feedback mechanism. To test this hypothesis. we conducted field studies in the temperate forest of the southern Andes, where introduced ungulates are a major source of anthropogenic alteration. For 10 animal-pollinated understory plants, we compared population density, pollinator visitation, pollen deposition in stigmas, and reproduction in four pairs of grazed and ungrazed sites. We found evidence of indirect effects of ungulates on pollination and reproduction only for the herb Aistroemeria aurea (Alstroemeriaceae). The general lack of evidence for indirect effects on most of the species may result from resistance to cattle browsing and trampling, or low statistical power. For A. aurea, we present additional evidence from trampling and hand-pollination experiments, plus path analyses of the effect of density on pollination and reproduction showing that: (1) cattle decrease the absolute and relative population density of this species through trampling; (2) density, particularly relative density, affects pollen deposition on stigmas; and (3) conspecific pollen deposition affects reproduction. Thus, our results indicate that, by directly reducing the population density of A. aurea, cattle are indirectly affecting its reproduction. [ABSTRACT FROM AUTHOR]

Long-term conservation of biodiversity may depend not only on the maintenance of its component parts but also on their interactions. Here we provide strong evidence that an introduced species is able to affect the network of interactions among coexisting species. We studied plant–pollinator interactions in native forest sites with and without domestic cattle and used these data to construct plant–pollinator interaction networks. Results from nonmetric multidimensional scaling and permutation tests suggest that the presence of cattle has significantly modified the structure of the plant–pollinator interaction network. The effect of cattle on network structure was mainly because of the modification of a few highly frequent interactions, which are likely important from a functional perspective. This overwhelming influence of a few interactions on observed community patterns should serve as a caution to those studying community and ecosystem properties. [ABSTRACT FROM AUTHOR]

Recent studies have suggested that plant-pollinator interactions may be less specialized than previously thought. We contrasted patterns of specialization observed in five plant-pollinator interaction webs with predictions based on null models. In the five data sets the observed number of extreme specialists and extreme generalists was significantly higher than the null expectation. This pattern was mostly due to a positive correlation between species frequency of interaction (f) and their estimated degree of generalization (s). After accounting for this association, the expected frequency distribution of degree of specialization generated by the null model closely matched the observed frequency distribution in the five data sets. A second null model which explicitly incorporated the correlation between f and s, also generated expected frequency distributions of specialization that closely resemble those observed in the data sets. To make progress in understanding the distribution of degree of specialization m pollination systems it will be necessary nor only to improve the quality of the data and to refine methods used to quantify specialization, but also to answer the question of why more frequently interacting species appear to be more generalized. [ABSTRACT FROM AUTHOR]

Under a metacommunity framework, the spatial configuration of habitat fragments could determine local community structure. Yet, quantifying fragment connectivity is challenging, as it depends on multiple variables at several geographical scales. We assessed the extent to which fragment connectivity and area explain patterns in interaction structure among four herbivore guilds and their host plants in a metacommunity. We propose an integrative connectivity metric including geographic distance, neighboring fragment area and similarity in resource composition as an extension of Hanski's classic metric. We then used nonlinear models to assess whether fragment connectivity and area predicted link richness and similarity in link composition. We found that link richness was always negatively related to connectivity but at different geographic scales depending on the herbivore guild. In contrast, while link composition was also related to connectivity, the direction and strength of this relationship varied among herbivore guilds and type of link composition (qualitative or quantitative). Furthermore, focal fragment area was not an important determinant of interaction diversity in local communities. Our findings emphasize resource similarity as a novel dimension of fragment connectivity relevant in explaining interaction diversity patterns in natural trophic networks. [ABSTRACT FROM AUTHOR]