Why does the magnitude of genotype‐by‐environment interaction vary?

Genotype‐by‐environment interaction (G × E), that is, genetic variation in phenotypic plasticity, is a central concept in ecology and evolutionary biology. G×E has wide‐ranging implications for trait development and for understanding how organisms will respond to environmental change. Although G × E has been extensively documented, its presence and magnitude vary dramatically across populations and traits. Despite this, we still know little about why G × E is so evident in some traits and populations, but minimal or absent in others. To encourage synthetic research in this area, we review diverse hypotheses for the underlying biological causes of variation in G × E. We extract common themes from these hypotheses to develop a more synthetic understanding of variation in G × E and suggest some important next steps.     

A patch-dynamics approach to savanna dynamics and woody plant encroachment – Insights from an arid savanna

The coexistence of woody and grassy plants in savannas has often been attributed to a rooting-niche separation (two-layer hypothesis). Water was assumed to be the limiting resource for both growth forms and grasses were assumed to extract water from the upper soil layer and trees and bushes from the lower layers. Woody plant encroachment (i.e. an increase in density of woody plants often unpalatable to domestic livestock) is a serious problem in many savannas and is believed to be the result of overgrazing in ‘two-layer systems’. Recent research has questioned the universality of both the two-layer hypothesis and the hypothesis that overgrazing is the cause of woody plant encroachment.

We present an alternative hypothesis explaining both tree–grass coexistence and woody plant encroachment in arid savannas. We propose that woody plant encroachment is part of a cyclical succession between open savanna and woody dominance and is driven by two factors: rainfall that is highly variable in space and time, and inter-tree competition. In this case, savanna landscapes are composed of many patches (a few hectares in size) in different states of transition between grassy and woody dominance, i.e. we hypothesize that arid savannas are patch-dynamic systems. We summarize patterns of tree distribution observed in an arid savanna in Namibia and show that these patterns are in agreement with the patch-dynamic savanna hypothesis. We discuss the applicability of this hypothesis to fire-dominated savannas, in which rainfall variability is low and fire drives spatial heterogeneity.

We conclude that field studies are more likely to contribute to a general understanding of tree–grass coexistence and woody plant encroachment if they consider both primary (rain and nutrients) and secondary (fire and grazing) determinants of patch properties across different savannas.     

Anticipated effects of abiotic environmental change on intraspecific social interactions

Social interactions are ubiquitous across the animal kingdom. A variety of ecological and evolutionary processes are dependent on social interactions, such as movement, disease spread, information transmission, and density-dependent reproduction and survival. Social interactions, like any behaviour, are context dependent, varying with environmental conditions. Currently, environments are changing rapidly across multiple dimensions, becoming warmer and more variable, while habitats are increasingly fragmented and contaminated with pollutants. Social interactions are expected to change in response to these stressors and to continue to change into the future. However, a comprehensive understanding of the form and magnitude of the effects of these environmental changes on social interactions is currently lacking. Focusing on four major forms of rapid environmental change currently occurring, we review how these changing environmental gradients are expected to have immediate effects on social interactions such as communication, agonistic behaviours, and group formation, which will thereby induce changes in social organisation including mating systems, dominance hierarchies, and collective behaviour. Our review covers intraspecific variation in social interactions across environments, including studies in both the wild and in laboratory settings, and across a range of taxa. The expected responses of social behaviour to environmental change are diverse, but we identify several general themes. First, very dry, variable, fragmented, or polluted environments are likely to destabilise existing social systems. This occurs as these conditions limit the energy available for complex social interactions and affect dissimilar phenotypes differently. Second, a given environmental change can lead to opposite responses in social behaviour, and the direction of the response often hinges on the natural history of the organism in question. Third, our review highlights the fact that changes in environmental factors are not occurring in isolation: multiple factors are changing simultaneously, which may have antagonistic or synergistic effects, and more work should be done to understand these combined effects. We close by identifying methodological and analytical techniques that might help to study the response of social interactions to changing environments, highlight consistent patterns among taxa, and predict subsequent evolutionary change. We expect that the changes in social interactions that we document here will have consequences for individuals, groups, and for the ecology and evolution of populations, and therefore warrant a central place in the study of animal populations, particularly in an era of rapid environmental change.     

Effect of nest-site microclimatic conditions on nesting success in the Lesser Kestrel Falco naumanni

Capsule: Microclimatic conditions in the nests of the Lesser Kestrel Falco naumanni, particularly the percentage of time of extremely low humidity, affect breeding success.

Aim: To study the effect of within-nest temperature and humidity on nest productivity, and the correlation between nest productivity and the order of dates on which nests were occupied by the parents. To compare microclimatic conditions in the nest, breeding success and order of occupation between nests under tile roofs and in artificial nest boxes.

Methods: Three different Lesser Kestrel colonies were monitored in Israel – one rural, one urban and one in an open country habitat. Data loggers were placed in 39 nests for the entire breeding period to measure temperature and humidity. The number of fledglings was recorded for each nest, as well as the date of occupation.

Results: Full microclimatic data from 35 nests suggest that percentage of time of extremely low humidity is the major predictor of nest productivity – low humidity is negatively correlated with nest productivity. Sites of more successful nests were occupied earlier. Considering only successful nests, the urban colony had the lowest breeding success of the three colonies. There was no significant difference in mean productivity between nests in roofs and nest boxes, but nests in roofs were occupied earlier.

Conclusion: Nest microclimate, particularly low humidity, affects nesting success in addition to colony location.     

The chemokine receptors ACKR2 and CCR2 reciprocally regulate lymphatic vessel density

Macrophages regulate lymphatic vasculature development; however, the molecular mechanisms regulating their recruitment to developing, and adult, lymphatic vascular sites are not known. Here, we report that resting mice deficient for the inflammatory chemokine‐scavenging receptor, ACKR2, display increased lymphatic vessel density in a range of tissues under resting and regenerating conditions. This appears not to alter dendritic cell migration to draining lymph nodes but is associated with enhanced fluid drainage from peripheral tissues and thus with a hypotensive phenotype. Examination of embryonic skin revealed that this lymphatic vessel density phenotype is developmentally established. Further studies indicated that macrophages and the inflammatory CC‐chemokine CCL2, which is scavenged by ACKR2, are associated with this phenotype. Accordingly, mice deficient for the CCL2 signalling receptor, CCR2, displayed a reciprocal phenotype of reduced lymphatic vessel density. Further examination revealed that proximity of pro‐lymphangiogenic macrophages to developing lymphatic vessel surfaces is increased in ACKR2‐deficient mice and reduced in CCR2‐deficient mice. Therefore, these receptors regulate vessel density by reciprocally modulating pro‐lymphangiogenic macrophage recruitment, and proximity, to developing, resting and regenerating lymphatic vessels.     

Comparison of low and high dose cosyntropin stimulation tests in the diagnosis of adrenal insufficiency in septic shock patients

Stress situations such as septic shock are accompanied by activation of the HPA axis. Some patients do not activate this axis in stress situations. This blunted response is currently designated as critical illness-related corticosteroid insufficiency (CIRCI). Currently the 250 μg cosyntropin stimulation test is the preferred diagnostic test for CIRCI. Few papers explored the role of the 1 μg cosyntropin test in septic shock patients. In this study, we compared both tests in septic shock patients taking a special interest in the population with intermediary baseline cortisol. Prospective noninterventional study included 74 septic shock patients. After measurement of baseline cortisol all patients received 1 μg of cosyntropin i. v. and 4 h later 249 μg of cosyntropin. We compared the cortisol increase after each test and its relation to mortality and vasopressor therapy. There was a moderate correlation in response to low and high dose cosyntropin, r(s)=0.55. This correlation in patients with baseline cortisol between 10-34 μg/dl is, r(s)=0.67. The increase induced by both tests was equally accurate to identify mortality and time of vasopressor withdrawal. Low and high dose cosyntropin tests presented a moderate correlation in patients with baseline cortisol between 10-34 μg/dl. Both tests are equally accurate to identify mortality and time of vasopressor therapy. These results suggest that both tests could be used to diagnose CIRCI.     

caGrid: design and implementation of the core architecture of the cancer biomedical informatics grid

MOTIVATION: The complexity of cancer is prompting researchers to find new ways to synthesize information from diverse data sources and to carry out coordinated research efforts that span multiple institutions. There is a need for standard applications, common data models, and software infrastructure to enable more efficient access to and sharing of distributed computational resources in cancer research. To address this need the National Cancer Institute (NCI) has initiated a national-scale effort, called the cancer Biomedical Informatics Grid (caBIGtrade mark), to develop a federation of interoperable research information systems. RESULTS: At the heart of the caBIG approach to federated interoperability effort is a Grid middleware infrastructure, called caGrid. In this paper we describe the caGrid framework and its current implementation, caGrid version 0.5. caGrid is a model-driven and service-oriented architecture that synthesizes and extends a number of technologies to provide a standardized framework for the advertising, discovery, and invocation of data and analytical resources. We expect caGrid to greatly facilitate the launch and ongoing management of coordinated cancer research studies involving multiple institutions, to provide the ability to manage and securely share information and analytic resources, and to spur a new generation of research applications that empower researchers to take a more integrative, trans-domain approach to data mining and analysis. AVAILABILITY: The caGrid version 0.5 release can be downloaded from https://cabig.nci.nih.gov/workspaces/Architecture/caGrid/. The operational test bed Grid can be accessed through the client included in the release, or through the caGrid-browser web application http://cagrid-browser.nci.nih.gov.     

Salivary and serum procalcitonin and C-reactive protein as biomarkers of periodontitis in United States veterans with osteoarthritis or rheumatoid arthritis

Serum procalcitonin (ProCT) is elevated in response to bacterial infections, whereas high sensitivity C-reactive protein (hsCRP) is a nonspecific inflammatory marker that is increased by excess adipose tissue. We examined the efficacy of ProCT and hsCRP as biomarkers of periodontitis in the saliva and serum of patients with arthritis, which is characterized by variable levels of systemic inflammation that potentially can confound the interpretation of inflammatory biomarkers. Blood and unstimulated whole saliva were collected from 33 patients with rheumatoid arthritis (RA) and 50 with osteoarthritis (OA). Periodontal status was assessed by full mouth examination and patients were categorized as having no/mild, moderate or severe periodontitis by standard parameters. Salivary and serum ProCT and hsCRP concentrations were compared. BMI, diabetes, anti-inflammatory medications and smoking status were ascertained from the patient records. Differences between OA and RA in proportionate numbers of patients were compared for race, gender, diabetes, adiposity and smoking status. Serum ProCT was significantly higher in arthritis patients with moderate to severe and severe periodontitis compared with no/mild periodontitis patients. There were no significant differences in salivary ProCT or salivary or serum hsCRP in RA patients related to periodontitis category. Most of the OA and RA patients were middle aged or older, 28.9% were diabetic, 78.3% were overweight or obese, and slightly more than half were either current or past smokers. The OA and RA groups differed by race, but not gender; blacks and males were predominant in both groups. The OA and RA groups did not differ in terms of controlled or uncontrolled diabetes, smoking status or BMI. The RA patients had been prescribed more anti-inflammatory medication than the OA patients. Our results demonstrate that circulating ProCT is a more discriminative biomarker for periodontitis than serum hsCRP in patients with underlying arthritis. Any elevation in salivary and serum hsCRP due to periodontitis apparently was overshadowed by differences among these patients in factors that influence CRP, such as the extent of inflammation between RA and OA, the extent of adipose tissue, the use of anti- inflammatory medications and smoking status. Although our study showed no differences in salivary ProCT related to severity of periodontitis, this biomarker also may be useful with further refinement.     

Urinary cortisol and urea nitrogen responses in irreversibly undernourished mule deer fawns

We examined the concentration of urinary cortisol and urea nitrogen of five hand-reared mule deer (Odocoileus hemionus) fawns that failed to recover from winter starvation, and compared them to levels found in fawns that recovered. The fawns wintered in fenced pastures stocked with wild deer, and were put back on supplemental feed after losing 15% of their body mass. The five fawns that died began receiving supplemental feed up to 3 wk before death. All continued to lose weight, and were consequently removed from the pasture and fed ad libitum 4 to 10 days before death. In the animals that died, cortisol levels continued to increase regardless of food availability, and were correlated with those of urea nitrogen. Postmortem cortisol and urea nitrogen measurements were significantly greater than concentrations found in the weeks preceding death. We hypothesize that uncontrolled protein catabolism is promoted by high levels of cortisol. These cortisol levels may reach a point at which irreversible multiple-system organ failure occurs, leading to the animal's death.