Humans are modifying the availability of nutrients such as nitrogen (N) and phosphorus (P), and it is therefore important to understand how these nutrients, independently or in combination, influence ...the growth and nutrient content of primary producers. Using meta-analysis of 118 field and laboratory experiments in freshwater, marine and terrestrial ecosystems, we tested hypotheses about co-limitation of N and P by comparing the effects of adding N alone, P alone, and both N and P together on internal N (e.g. %N, C:N) and P (e.g. %P, C:P) concentrations in autotroph communities. In particular, we tested the following predictions. First, if only one nutrient was limiting, addition of that nutrient should decrease the concentration of the other nutrient, but addition of the non-limiting nutrient would have no effect on the internal concentration of the limiting nutrient. If community co-limitation was occurring then addition of either nutrient should result in a decrease in the internal concentration of the other nutrient. Community co-limitation could also result in no change – or even an increase – in N concentrations in response to P addition if P stimulated growth of N fixers. Finally, if biochemically dependent colimitation was occurring, addition of a limiting nutrient would not decrease, and could even increase, the concentration of the other, co-limited nutrient. We found no general evidence for the decrease in the internal concentration of one nutrient due to addition of another nutrient. The one exception to this overall pattern was marine systems, where N addition decreased internal P concentrations. In contrast, P addition increased internal N concentrations across all experiments, consistent with co-limitation. These results have important implications for understanding the roles that N and P play in controlling producer growth and internal nutrient accumulation as well as for managing the effects of nutrient enrichment in ecosystems.
Synthesis
On a global scale, humans have doubled nitrogen (N) inputs and quadrupled phosphorus (P) inputs relative to pre-industrial levels. N and P fertilization influences autotroph internal nutrient concentrations and ratios and thereby affects a variety of community and ecosystem processes, including decomposition and consumer population dynamics. It is therefore critical to understand the effects of nutrient additions on the growth and nutrient concentrations of primary producers. We used meta-analysis to evaluate the responses of autotroph internal N and P concentrations to additions of N, P, and N+P and make inferences about limitation and co-limitation of N and P across marine, terrestrial, and freshwater ecosystems. We found little evidence for single-nutrient limitation, highlighting the fact that multiple nutrients generally limit primary production.
How ecosystem productivity and species richness are interrelated is one of the most debated subjects in the history of ecology. Decades of intensive study have yet to discern the actual mechanisms ...behind observed global patterns. Here, by integrating the predictions from multiple theories into a single model and using data from 1,126 grassland plots spanning five continents, we detect the clear signals of numerous underlying mechanisms linking productivity and richness. We find that an integrative model has substantially higher explanatory power than traditional bivariate analyses. In addition, the specific results unveil several surprising findings that conflict with classical models. These include the isolation of a strong and consistent enhancement of productivity by richness, an effect in striking contrast with superficial data patterns. Also revealed is a consistent importance of competition across the full range of productivity values, in direct conflict with some (but not all) proposed models. The promotion of local richness by macroecological gradients in climatic favourability, generally seen as a competing hypothesis, is also found to be important in our analysis. The results demonstrate that an integrative modelling approach leads to a major advance in our ability to discern the underlying processes operating in ecological systems.
Climatic warming is a primary driver of change in ecosystems worldwide. Here, we synthesize responses of species richness and evenness from 187 experimental warming studies in a quantitative ...meta‐analysis. We asked 1) whether effects of warming on diversity were detectable and consistent across terrestrial, freshwater and marine ecosystems, 2) if effects on diversity correlated with intensity, duration, and experimental unit size of temperature change manipulations, and 3) whether these experimental effects on diversity interacted with ecosystem types. Using multilevel mixed linear models and model averaging, we also tested the relative importance of variables that described uncontrolled environmental variation and attributes of experimental units. Overall, experimental warming reduced richness across ecosystems (mean log‐response ratio = –0.091, 95% bootstrapped CI: –0.13, –0.05) representing an 8.9% decline relative to ambient temperature treatments. Richness did not change in response to warming in freshwater systems, but was more strongly negative in terrestrial (–11.8%) and marine (–10.5%) experiments. In contrast, warming impacts on evenness were neutral overall and in aquatic systems, but weakly negative on land (7.6%). Intensity and duration of experimental warming did not explain variation in diversity responses, but negative effects on richness were stronger in smaller experimental units, particularly in marine systems. Model‐averaged parameter estimation confirmed these main effects while accounting for variation in latitude, ambient temperature at the sites of manipulations, venue (field versus lab), community trophic type, and whether experiments were open or closed to colonization. These analyses synthesize extensive experimental evidence showing declines in local richness with increased temperature, particularly in terrestrial and marine communities. However, the more variable effects of warming on evenness were better explained by the random effect of site identity, suggesting that effects on species’ relative abundances were contingent on local species composition.
Synthesis
A global research priority is to understand the consequences of climate change for biodiversity. A growing number of experimental studies have manipulated climatic drivers, in particular changes in temperature, in local communities. In the first quantitative meta‐analysis of community‐level studies across freshwater, marine and terrestrial experiments, species richness declined consistently with experimental warming. This effect was insensitive to warming intensity, duration, and multiple environmental and procedural covariates. However, evenness responses were weakly negative only in terrestrial systems and more variable across ecosystem types. Linear mixed model analyses revealed that the identity of local sites explained nearly 50% of variance in evenness effect sizes, compared to only 10% for richness. This result provides evidence that local species composition strongly constrains changes in relative species abundances in response to warming.
Theory on trophic interactions predicts that predators increase plant biomass by feeding on herbivores, an indirect interaction called a trophic cascade. Theory also predicts that predators feeding ...on predators, or intraguild predation, will weaken trophic cascades. Although past syntheses have confirmed cascading effects of terrestrial arthropod predators, we lack a comprehensive analysis for vertebrate insectivores—which by virtue of their body size and feeding habits are often top predators in these systems—and of how intraguild predation mediates trophic cascade strength. We report here on a meta-analysis of 113 experiments documenting the effects of insectivorous birds, bats, or lizards on predaceous arthropods, herbivorous arthropods, and plants. Although vertebrate insectivores fed as intraguild predators, strongly reducing predaceous arthropods (38%), they nevertheless suppressed herbivores (39%), indirectly reduced plant damage (40%), and increased plant biomass (14%). Furthermore, effects of vertebrate insectivores on predatory and herbivorous arthropods were positively correlated. Effects were strongest on arthropods and plants in communities with abundant predaceous arthropods and strong intraguild predation, but weak in communities depauperate in arthropod predators and intraguild predation. The naturally occurring ratio of arthropod predators relative to herbivores varied tremendously among the studied communities, and the skew to predators increased with site primary productivity and in trees relative to shrubs. Although intraguild predation among arthropod predators has been shown to weaken herbivore suppression, we find this paradigm does not extend to vertebrate insectivores in these communities. Instead, vertebrate intraguild predation is associated with strengthened trophic cascades, and insectivores function as dominant predators in terrestrial plant-arthropod communities.
Background
ProGlide is a percutaneous suture‐mediated closure device used in arterial and venous closure following percutaneous intervention. Risk of vascular complications from use, particularly ...related to failure in hemostasis, or acute vessel closure, remains significant and often related to improper suture deployment. We describe a technique of ultrasound‐guided ProGlide deployment in transfemoral transcatheter aortic valve implantation (TF‐TAVI).
Aims
The aim of this study is to assess vascular outcomes for ultrasound‐guided deployment of ProGlide vascular closure devices in patients undergoing TF‐TAVI.
Methods
We collected relevant clinical data of patients undergoing TAVI in a large volume centre. Primary outcome: main access Valve Academic Research Consortium 3 (VARC‐3) major vascular complication. Secondary outcome: any major/minor VARC‐3 vascular complication, its type (bleed or ischemia), and treatment required (medical, percutaneous, or surgical). We performed inverse weighting propensity score analysis to compare the population undergoing ultrasound‐guided versus conventional ProGlide deployment for main TAVI access. Ultrasound technique for ProGlide insertion was performed as described below.
Results
Five hundred and seventeen patients undergoing TF‐TAVI were included.
Primary outcome: In 126 (ultrasound‐guided) and 391 (conventional ProGlide insertion), 0% versus 1.8% (p < 0.001) had a major VARC‐3 vascular complication, respectively.
Secondary outcome: 0.8% (one minor VARC‐3 bleed) vs 4.1% (13 bleeds and three occlusions) had any VARC‐3 vascular complication (major and minor) (p < 0.001). Surgical treatment of vascular complication was required in 0.8% versus 1.3% (p = NS).
Conclusions
Ultrasound‐guided deployment of ProGlide for vascular closure reduced the risk of major vascular complications in a large population undergoing TAVI.
Niche dimensionality provides a general theoretical explanation for biodiversity-more niches, defined by more limiting factors, allow for more ways that species can coexist. Because plant species ...compete for the same set of limiting resources, theory predicts that addition of a limiting resource eliminates potential trade-offs, reducing the number of species that can coexist. Multiple nutrient limitation of plant production is common and therefore fertilization may reduce diversity by reducing the number or dimensionality of belowground limiting factors. At the same time, nutrient addition, by increasing biomass, should ultimately shift competition from belowground nutrients towards a one-dimensional competitive trade-off for light. Here we show that plant species diversity decreased when a greater number of limiting nutrients were added across 45 grassland sites from a multi-continent experimental network. The number of added nutrients predicted diversity loss, even after controlling for effects of plant biomass, and even where biomass production was not nutrient-limited. We found that elevated resource supply reduced niche dimensionality and diversity and increased both productivity and compositional turnover. Our results point to the importance of understanding dimensionality in ecological systems that are undergoing diversity loss in response to multiple global change factors.
Forest structural diversity and its spatiotemporal variability are constrained by environmental and biological factors, including species pools, climate, land‐use history, and legacies of disturbance ...regimes. These factors influence forest responses to disturbances and their interactions with structural diversity, potentially creating structurally mediated emergent properties at local to continental spatial scales and over evolutionary time. Here, we present a conceptual framework for exploring the emergent properties that arise from interactions between forest structural diversity and disturbances. We synthesize and present definitions for key terms, including emergent property, disturbance, and resilience, and highlight various types and examples of emergent properties, such as (1) interactions with species composition, (2) interactions with disturbance frequency and intensity, and (3) evolutionary changes to communities. Although emergent properties in forest ecosystems remain poorly understood, we describe a foundation for study and applied management of forest structural diversity to enhance forest restoration and resilience.
Climate-driven global change is shifting the distribution and abundance of foundation species that form the base of ecosystems. The corresponding responses of inhabitant species to shifts in ...habitat-forming species are poorly understood, however we expect community responses to depend on how species perceive habitat patches and sort among them, particularly along range edges. We used the poleward shift of a mangrove–marsh ecotone to evaluate sorting of marine macrofauna (small fish and decapod crustaceans) among vegetation patches at a series of nested scales. Within the mangrove–marsh ecotone, we deployed retrievable panels of artificial vegetation structures mimicking a marsh grass and two mangrove species in patches dominated by each of these three foundation species. Over six months, we observed macrofaunal sorting by physical structure, isolated on panels, and by patch type, which included stand-level attributes such as production, shading, and chemical cues. We found multiscale partitioning of macrofaunal community composition by site (kilometer scale), vegetation type, and patch type with stand attributes (meters), and physical structure (centimeters). Differences in community composition between vegetation types at each scale indicated that mangroves and marsh grass differ as habitat for marine fauna and that wetland inhabitants can distinguish and sort among fine-grain habitat patches that co-occur within the ecotone. Such differences suggest that shifts in wetland vegetation are consequential for the protection and management of coastal populations. Studies that determine which habitat attributes shape inhabitant fauna associations can help reveal not just the spatial grain at which inhabitants associate with emerging frontier habitat but also how the redistribution of foundation species shapes the pace and resolution of broader community change.
The dynamic structure of ecological communities results from interactions among taxa that change with shifts in species composition in space and time. However, our ability to study the interplay of ...ecological and evolutionary processes on community assembly remains relatively unexplored due to the difficulty of measuring community structure over long temporal scales. Here, we made use of a geological chronosequence across the Hawaiian Islands, representing 50 years to 4.15 million years of ecosystem development, to sample 11 communities of arthropods and their associated plant taxa using semiquantitative DNA metabarcoding. We then examined how ecological communities changed with community age by calculating quantitative network statistics for bipartite networks of arthropod–plant associations. The average number of interactions per species (linkage density), ratio of plant to arthropod species (vulnerability) and uniformity of energy flow (interaction evenness) increased significantly in concert with community age. The index of specialization H2′ has a curvilinear relationship with community age. Our analyses suggest that younger communities are characterized by fewer but stronger interactions, while biotic associations become more even and diverse as communities mature. These shifts in structure became especially prominent on East Maui (~0.5 million years old) and older volcanos, after enough time had elapsed for adaptation and specialization to act on populations in situ. Such natural progression of specialization during community assembly is probably impeded by the rapid infiltration of non‐native species, with special risk to younger or more recently disturbed communities that are composed of fewer specialized relationships.
Islands are widely considered to be model systems for studying fundamental questions in ecology and evolutionary biology. The fundamental state factors that vary among island systems – geologic ...history, size, isolation and age – form the basis of mature phenomenological and predictive theory. In this review, we first highlight classic lines of inquiry that exemplify the historical and continuing importance of islands. We then show how the conceptual power of islands as ‘natural laboratories’ can be improved through functional classifications of both the biological properties of, and human impact on, insular systems. We highlight how global environmental change has been accentuated on islands, expressly because of their unique insular properties. We review five categories of environmental perturbation: climate change, habitat modification, direct exploitation, invasion and disease. Using an analysis of taxonomic checklists for the arthropod biotas of three well-studied island archipelagos, we show how taxonomists are meeting the challenge of biodiversity assessment before the biodiversity disappears. Our aim is to promote discussion on the tight correlations of the environmental health of insular systems to their continued importance as singular venues for discovery in ecology and evolutionary biology, as well as to their conservation significance as hotspots of endemism.
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