A Pleistocene legacy structures variation in modern seagrass ecosystems.

Distribution of Earth's biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate-trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth's environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass (Zostera marina), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems.

Climate drives the geography of marine consumption by changing predator communities.

The global distribution of primary production and consumption by humans (fisheries) is well-documented, but we have no map linking the central ecological process of consumption within food webs to temperature and other ecological drivers. Using standardized assays that span 105° of latitude on four continents, we show that rates of bait consumption by generalist predators in shallow marine ecosystems are tightly linked to both temperature and the composition of consumer assemblages. Unexpectedly, rates of consumption peaked at midlatitudes (25 to 35°) in both Northern and Southern Hemispheres across both seagrass and unvegetated sediment habitats. This pattern contrasts with terrestrial systems, where biotic interactions reportedly weaken away from the equator, but it parallels an emerging pattern of a subtropical peak in marine biodiversity. The higher consumption at midlatitudes was closely related to the type of consumers present, which explained rates of consumption better than consumer density, biomass, species diversity, or habitat. Indeed, the apparent effect of temperature on consumption was mostly driven by temperature-associated turnover in consumer community composition. Our findings reinforce the key influence of climate warming on altered species composition and highlight its implications for the functioning of Earth's ecosystems.

The biogeography of community assembly: latitude and predation drive variation in community trait distribution in a guild of epifaunal crustaceans.

While considerable evidence exists of biogeographic patterns in the intensity of species interactions, the influence of these patterns on variation in community structure is less clear. Studying how the distributions of traits in communities vary along global gradients can inform how variation in interactions and other factors contribute to the process of community assembly. Using a model selection approach on measures of trait dispersion in crustaceans associated with eelgrass (Zostera marina) spanning 30° of latitude in two oceans, we found that dispersion strongly increased with increasing predation and decreasing latitude. Ocean and epiphyte load appeared as secondary predictors; Pacific communities were more overdispersed while Atlantic communities were more clustered, and increasing epiphytes were associated with increased clustering. By examining how species interactions and environmental filters influence community structure across biogeographic regions, we demonstrate how both latitudinal variation in species interactions and historical contingency shape these responses. Community trait distributions have implications for ecosystem stability and functioning, and integrating large-scale observations of environmental filters, species interactions and traits can help us predict how communities may respond to environmental change.

Latitude, temperature, and habitat complexity predict predation pressure in eelgrass beds across the Northern Hemisphere.

Latitudinal gradients in species interactions are widely cited as potential causes or consequences of global patterns of biodiversity. However, mechanistic studies documenting changes in interactions across broad geographic ranges are limited. We surveyed predation intensity on common prey (live amphipods and gastropods) in communities of eelgrass (Zostera marina) at 48 sites across its Northern Hemisphere range, encompassing over 37° of latitude and four continental coastlines. Predation on amphipods declined with latitude on all coasts but declined more strongly along western ocean margins where temperature gradients are steeper. Whereas in situ water temperature at the time of the experiments was uncorrelated with predation, mean annual temperature strongly positively predicted predation, suggesting a more complex mechanism than simply increased metabolic activity at the time of predation. This large-scale biogeographic pattern was modified by local habitat characteristics; predation declined with higher shoot density both among and within sites. Predation rates on gastropods, by contrast, were uniformly low and varied little among sites. The high replication and geographic extent of our study not only provides additional evidence to support biogeographic variation in predation intensity, but also insight into the mechanisms that relate temperature and biogeographic gradients in species interactions.

A call to incorporate systems theory and human factors into the existing investigation of harm in clinical research involving healthcare products.

This is a joint statement from individual pharmacology and pharmaceutical professionals acting in their own capacity, including members of the Alliance for Clinical Research Excellence and Safety (ACRES) and the International Society of Pharmacovigilance (ISoP). By building on the extensive pharmacological and regulatory investigations that already take place, we are calling for a fuller and more robust systems-based approach to the independent investigation of clinical research when serious incidents of harm occur, starting with first-in-human clinical trials. To complement existing activities and regulations, we propose an additional approach blending evidence derived from both pharmacological and organizational science, which addresses human factors and transparency, to enhance organizational learning and continuous improvement. As happens with investigations in other sectors of society, such as the chemical and aviation sector, this systems approach should be seen as an additional way to understand how problems occur and how they might be prevented in the future. We believe that repetition of potentially preventable and adverse outcomes during clinical research, by failing to identify and act upon all systematic vulnerabilities, is a situation that needs urgent change. As we will discuss further on, approaches based on applying systems theory and human factors are much more likely to improve objectivity and transparency, leading to better system design.

Grazer diversity interacts with biogenic habitat heterogeneity to accelerate intertidal algal succession.

Environmental heterogeneity contributes to coexistence by allowing species with different traits to persist when different species perform best at different times or places. This interaction between niche differences and environmental variability may also help explain relationships between biodiversity and ecosystem functioning, but few data are available to rigorously evaluate this hypothesis. We assessed how a biologically relevant aspect of environmental heterogeneity interacts with species diversity to determine ecosystem processes in a natural rocky intertidal community. We used field removals to factorially manipulate biogenic habitat heterogeneity (barnacles, bare rock, and plots that were 50/50 mixes of the two habitat types) and gastropod grazer species richness and then tracked algal community succession and recovery over the course of 1 yr. We found that herbivore diversity, substrate heterogeneity, and their interaction played unique roles in the peak abundance and timing of occurrence of different algal functional groups. Early successional microalgae were most heavily grazed in diverse herbivore assemblages and those with barnacles present, which was likely due to complementary feeding strategies among all three grazers. In contrast, late successional macroalgae were strongly influenced by the presence of a habitat generalist limpet. In this herbivore's absence, heterogeneous habitats (i.e., mixtures of bare rock and barnacles) experienced the greatest algal accumulation, which was partly a result of complementary habitat use by the remaining herbivores. The complex way habitat identity and heterogeneity altered grazer-algal interactions in our study suggests species' differences and environmental heterogeneity both separately and interactively contribute to the relationship between biodiversity and ecosystem functions.

Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approach.

Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom-up and top-down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top-down and bottom-up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top-down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross-site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large-scale patterns corresponded strikingly with prior small-scale experiments. Our results link global and local evidence that biodiversity and top-down control strongly influence functioning of threatened seagrass ecosystems, and suggest that biodiversity is comparably important to global change stressors.

Temporal shifts in top-down vs. bottom-up control of epiphytic algae in a seagrass ecosystem.

In coastal marine food webs, small invertebrate herbivores (mesograzers) have long been hypothesized to occupy an important position facilitating dominance of habitat-forming macrophytes by grazing competitively superior epiphytic algae. Because of the difficulty of manipulating mesograzers in the field, however, their impacts on community organization have rarely been rigorously documented. Understanding mesograzer impacts has taken on increased urgency in seagrass systems due to declines in seagrasses globally, caused in part by widespread eutrophication favoring seagrass overgrowth by faster-growing algae. Using cage-free field experiments in two seasons (fall and summer), we present experimental confirmation that mesograzer reduction and nutrients can promote blooms of epiphytic algae growing on eelgrass (Zostera marina). In this study, nutrient additions increased epiphytes only in the fall following natural decline of mesograzers. In the summer, experimental mesograzer reduction stimulated a 447% increase in epiphytes, appearing to exacerbate seasonal dieback of eelgrass. Using structural equation modeling, we illuminate the temporal dynamics of complex interactions between macrophytes, mesograzers, and epiphytes in the summer experiment. An unexpected result emerged from investigating the interaction network: drift macroalgae indirectly reduced epiphytes by providing structure for mesograzers, suggesting that the net effect of macroalgae on seagrass depends on macroalgal density. Our results show that mesograzers can control proliferation of epiphytic algae, that top-down and bottom-up forcing are temporally variable, and that the presence of macroalgae can strengthen top-down control of epiphytic algae, potentially contributing to eelgrass persistence.

Physiological effects of diet mixing on consumer fitness: a meta-analysis.

The degree of dietary generalism among consumers has important consequences for population, community, and ecosystem processes, yet the effects on consumer fitness of mixing food types have not been examined comprehensively. We conducted a meta-analysis of 161 peer-reviewed studies reporting 493 experimental manipulations of prey diversity to test whether diet mixing enhances consumer fitness based on the intrinsic nutritional quality of foods and consumer physiology. Averaged across studies, mixed diets conferred significantly higher fitness than the average of single-species diets, but not the best single prey species. More than half of individual experiments, however, showed maximal growth and reproduction on mixed diets, consistent with the predicted benefits of a balanced diet. Mixed diets including chemically defended prey were no better than the average prey type, opposing the prediction that a diverse diet dilutes toxins. Finally, mixed-model analysis showed that the effect of diet mixing was stronger for herbivores than for higher trophic levels. The generally weak evidence for the nutritional benefits of diet mixing in these primarily laboratory experiments suggests that diet generalism is not strongly favored by the inherent physiological benefits of mixing food types, but is more likely driven by ecological and environmental influences on consumer foraging.

Heatwave restructures marine intertidal communities across a stress gradient.

Significant questions remain about how ecosystems that are structured by abiotic stress will be affected by climate change. Warmer temperatures are hypothesized to shift species along abiotic gradients such that distributions track changing environments where physical conditions allow. However, community-scale impacts of extreme warming in heterogeneous landscapes are likely to be more complex. We investigated the impacts of a multiyear marine heatwave on intertidal community dynamics and zonation on a wave-swept rocky coastline along the Central Coast of British Columbia, Canada. Leveraging an 8-year time series with high seaweed taxonomic resolution (116 taxa) that was established 3 years prior to the heatwave, we document major shifts in zonation and abundance of populations that led to substantial reorganization at the community level. The heatwave was associated with shifts in primary production away from upper elevations through declines in seaweed cover and partial replacement by invertebrates. At low elevations, seaweed cover remained stable or recovered rapidly following decline, being balanced by increases in some species and decreases in others. These results illustrate that, rather than shifting community zonation uniformly along abiotic stress gradients, intense and lasting warming events may restructure patterns of ecological dominance and reduce total habitability of ecosystems, especially at extreme ends of pre-existing abiotic gradients.

Theory and application of an improved species richness estimator.

Species richness is an essential biodiversity variable indicative of ecosystem states and rates of invasion, speciation and extinction both contemporarily and in fossil records. However, limited sampling effort and spatial aggregation of organisms mean that biodiversity surveys rarely observe every species in the survey area. Here we present a non-parametric, asymptotic and bias-minimized richness estimator, Ω by modelling how spatial abundance characteristics affect observation of species richness. Improved asymptotic estimators are critical when both absolute richness and difference detection are important. We conduct simulation tests and applied Ω to a tree census and a seaweed survey. Ω consistently outperforms other estimators in balancing bias, precision and difference detection accuracy. However, small difference detection is poor with any asymptotic estimator. An R-package, Richness, performs the proposed richness estimations along with other asymptotic estimators and bootstrapped precisions. Our results explain how natural and observer-induced variations affect species observation, how these factors can be used to correct observed richness using the estimator Ω on a variety of data, and why further improvements are critical for biodiversity assessments. This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'.

Above-Room-Temperature Ferromagnetism in Thin van der Waals Flakes of Cobalt-Substituted Fe5GeTe2.

Two-dimensional (2D) magnetic van der Waals materials provide a powerful platform for studying the fundamental physics of low-dimensional magnetism, engineering novel magnetic phases, and enabling thin and highly tunable spintronic devices. To realize high-quality and practical devices for such applications, there is a critical need for robust 2D magnets with ordering temperatures above room temperature that can be created via exfoliation. Here, the study of exfoliated flakes of cobalt-substituted Fe5GeTe2 (CFGT) exhibiting magnetism above room temperature is reported. Via quantum magnetic imaging with nitrogen-vacancy centers in diamond, ferromagnetism at room temperature was observed in CFGT flakes as thin as 16 nm corresponding to 16 layers. This result expands the portfolio of thin room-temperature 2D magnet flakes exfoliated from robust single crystals that reach a thickness regime relevant to practical spintronic applications. The Curie temperature Tc of CFGT ranges from 310 K in the thinnest flake studied to 328 K in the bulk. To investigate the prospect of high-temperature monolayer ferromagnetism, Monte Carlo calculations were performed, which predicted a high value of Tc of ∼270 K in CFGT monolayers. Pathways toward further enhancing monolayer Tc are discussed. These results support CFGT as a promising platform for realizing high-quality room-temperature 2D magnet devices.

The developmental high wire: Balancing resource investment in immunity and reproduction.

The strategic allocation of resources into immunity poses a unique challenge for individuals, where infection at different stages of development may result in unique trade-offs with concurrent physiological processes or future fitness-enhancing traits. Here, we experimentally induced an immune challenge in female Gryllus firmus crickets to test whether illness at discrete life stages differentially impacts fitness. We injected heat-killed Serratia marcescens bacteria into antepenultimate juveniles, penultimate juveniles, sexually immature adults, and sexually mature adults, and then measured body growth, instar duration, mating rate, viability of stored sperm, egg production, oviposition rate, and egg viability. Immune activation significantly impacted reproductive traits, where females that were immune challenged as adults had decreased mating success and decreased egg viability compared to healthy individuals or females that were immune challenged as juveniles. Although there was no effect of an immune challenge on the other traits measured, the stress of handling resulted in reduced mass gain and smaller adult body size in females from the juvenile treatments, and females in the adult treatments suffered from reduced viability of sperm stored within their spermatheca. In summary, we found that an immune challenge does have negative impacts on reproduction, but also that even minor acute stressors can have significant impacts on fitness-enhancing traits. These findings highlight that the factors affecting fitness can be complex and at times unpredictable, and that the consequences of illness are specific to when during an individual's life an immune challenge is induced.

Fluctuating Asymmetry in the Polymorphic Sand Cricket (Gryllus firmus): Are More Functionally Important Structures Always More Symmetric?

Fluctuating asymmetry (FA) may serve as a reliable indicator of the functional importance of structures within an organism. Primary locomotor structures often display lower levels of FA than other paired structures, highlighting that selection can maintain symmetry in fitness-enhancing traits. Polyphenic species represent an attractive model for studying the fine-scale relationship between trait form and function, because multiple morphs exhibit unique life history adaptations that rely on different traits to maximize fitness. Here, we investigated whether individuals of the wing polyphenic sand field cricket (Gryllus firmus) maintain higher levels of symmetry in the bilateral structures most vital for maximizing fitness based on their specific life history strategy. We quantified FA and directional asymmetry (DA) across a suite of key morphological structures indicative of investment in somatic growth, reproduction, and flight capability for males and females across the flight-capable longwing (LW) and flight-incapable shortwing (SW) morphs. Although we did not find significant differences in FA across traits, hindwings lacked DA that was found in all other structures. We predicted that functionally important traits should maintain a higher level of symmetry; however, locomotor compensation strategies may reduce the selective pressures on symmetry or developmental constraints may limit the optimization between trait form and function.

Effects of Student Physical Therapists on Clinical Instructor Productivity Across Settings in an Academic Medical Center.

BACKGROUND: Clinical education is an integral component of physical therapy education. Both benefits and barriers exist in clinical education, but 1 commonly stated barrier includes the perception that students have a negative impact on clinical instructor productivity. OBJECTIVE: The purposes of this study were to evaluate the productivity of physical therapist clinical instructors in an academic medical center before, during, and after clinical education experiences, determine if there are differences in productivity during clinical education experiences across settings, and compare clinical instructor productivity with that of therapists who did not have a student during the same time frames. DESIGN: A retrospective design examined productivity across 3 years in acute care, inpatient rehabilitation, outpatient orthopedics, and outpatient neurology. Mean daily productivity was computed, normalized to an 8-hour day, and averaged for each week of the year. Data were analyzed using a repeated-measures ANOVA. Post-hoc comparisons were made within each setting to compare therapists with a student to those without. The Bonferonni-correction was used to control for multiple comparisons. RESULTS: Clinical instructor productivity was significantly increased in outpatient orthopedics and inpatient rehabilitation, and approached significance in outpatient neurology, but was not significant in acute care. The presence of a student made clinical instructors more productive but had no effect on the productivity of other therapists in that setting during the same time frame. LIMITATIONS: We studied only 1 academic medical center and could not account for clinical instructor factors such as years of experience or student factors such as year in their program. CONCLUSIONS: Our results indicate that having a student increases productivity of therapists in various settings. Future studies should examine the impact of clinical instructor experience and student characteristics and should expand to other settings.

Vulnerability and Clinical Research: Mapping the Challenges for Stakeholders.

Beyond what are characterized as Special Populations in U.S. FDA regulatory considerations is vulnerability of patient populations in a broader context of international guidance. Such a review suggests a rich appreciation for the diversity of patients. Vulnerable patients' status and the associated patient protections are of growing interest in the clinical research environment. To participate in the current developments and reflections, we selected 12 international & recognized core documents that are discussing human research protections and identify all references to them pertinent to Vulnerables. This allows the identification of 15 different categories of Vulnerability, that we group in five kinds of challenges. We then map significant regulatory and ethical interpretations and their implications toward applying what Vulnerability constitutes for the stakeholder ecosystem and its evolving direction as part of the overall protection for patients, defined as a "chain of protection." Different levels of understanding are proposed: Who are vulnerable (a 'macro'-mapping), what is Vulnerability (a 'meso'-mapping) leading to applications with practical questions (a 'micro'-mapping). We offer this analysis and mapping for practical benefit to a range of stakeholders with staffs whose functional responsibilities indirectly or directly essentially touch the broad spectrum of involvement with patients. The practical application is for multi-stakeholder consideration of patients-as-subjects in research, especially for Sites and Ethics Committees/IRBs, given the extended efforts of "patient-centricity"-the 'how's' and 'what's' of including patients in the clinical research process from discovery to RWE and its implications. Also considered is the value of education and training purposes on the true diversity of patients so that sensitivity to such matters from protocol development through informed consent and privacy protections are taken into account in the era of "new science," technological advances, and expansion of clinical research investigators, patient populations, and types of non-traditional research sites.

Meta-Analysis of Reciprocal Linkages between Temperate Seagrasses and Waterfowl with Implications for Conservation.

Multi-trophic conservation and management strategies may be necessary if reciprocal linkages between primary producers and their consumers are strong. While herbivory on aquatic plants is well-studied, direct top-down control of seagrass populations has received comparatively little attention, particularly in temperate regions. Herein, we used qualitative and meta-analytic approaches to assess the scope and consequences of avian (primarily waterfowl) herbivory on temperate seagrasses of the genus Zostera. Meta-analyses revealed widespread evidence of spatio-temporal correlations between Zostera and waterfowl abundances as well as strong top-down effects of grazing on Zostera. We also documented the identity and diversity of avian species reported to consume Zostera and qualitatively assessed their potential to exert top-down control. Our results demonstrate that Zostera and their avian herbivores are ecologically linked and we suggest that bird herbivory may influence the spatial structure, composition, and functioning of the seagrass ecosystem. Therefore, the consequences of avian herbivory should be considered in the management of seagrass populations. Of particular concern are instances of seagrass overgrazing by waterfowl which result in long-term reductions in seagrass biomass or coverage, with subsequent impacts on local populations of waterfowl and other seagrass-affiliated species. While our results showed that bird density and type may affect the magnitude of the top-down effects of avian herbivory, empirical research on the strength, context-dependency, and indirect effects of waterfowl-Zostera interactions remains limited. For example, increased efforts that explicitly measure the effects of different functional groups of birds on seagrass abundance and/or document how climate change-driven shifts in waterfowl migratory patterns impact seagrass phenology and population structure will advance research programs for both ecologists and managers concerned with the joint conservation of both seagrasses and their avian herbivores.

The synergy of the whole: building a global system for clinical trials to accelerate medicines development.

PURPOSE: The pharmaceutical industry, once highly respected, productive, and profitable, is in the throes of major change driven by many forces, including economics, science, regulation, and ethics. A variety of initiatives and partnerships have been launched to improve efficiency and productivity but without significant effect because they have failed to consider the process as a system. METHODS: Addressing the challenges facing this complex endeavor requires more than modifications of individual processes; it requires a fully integrated application of systems thinking and an understanding of the desired goals and complex interactions among essential components and stakeholders of the whole. A multistakeholder collaborative effort, led by the Alliance for Clinical Research Excellence and Safety (ACRES), a global nonprofit organization operating in the public interest, is now under way to build a shared global system for clinical research. Its systems approach focuses on the interconnection of stakeholders at critical points of interaction within 4 operational domains: site development and support, quality management, information technology, and safety. The ACRES initiatives, Site Accreditation and Standards, Product Safety Culture, Global Ethical Review and Regulatory Innovation, and Quality Assurance and Safety, focus on building and implementing systems solutions. Underpinning these initiatives is an open, shared, integrated technology (site and optics and quality informatics initiative). FINDINGS: We describe the rationale, challenges, progress, and successes of this effort to date and lessons learned. The complexity and fragmentation of the intensely proprietary ecosystem of drug development, challenging regulatory climate, and magnitude of the endeavor itself pose significant challenges, but the economic, social, and scientific rewards will more than justify the effort. IMPLICATIONS: An effective alliance model requires a willingness of multiple stakeholders to work together to build a shared system within a noncompetitive space that will have major benefits for all, including better access to medicines, better health, and more productive lives.