scholarly journals Using changes in host demographic rates to reveal the effects of infection with hidden variable models

2020 ◽  
Author(s):  
Jake M. Ferguson ◽  
Andrea González-González ◽  
Johnathan A. Kaiser ◽  
Sara M. Winzer ◽  
Justin M. Anast ◽  
...  
Keyword(s):  
Longitudinal Studies ◽  
Population Level ◽  
Vital Rates ◽  
Hidden Variable ◽  
Demographic Rates ◽  
Public Health Data ◽  
Individual Effects ◽  
Wildlife Populations ◽  
The Individual ◽  
Hidden Variable Models

AbstractThe impacts of disease on host vital rates can be clearly demonstrated using longitudinal studies, but these studies can be expensive and logistically challenging. We examined the utility of hidden variable models to infer the individual effects of disease, caused by infection, from population-level measurements of survival and fecundity when longitudinal studies are not possible. Our approach seeks to explain temporal changes in population-level vital rates by coupling observed changes in the infection status of individuals to an epidemiological model. We tested the approach using both single and coinfection viral challenge experiments on populations of fruit flies (Drosophila melanogaster). Specifically, we determined whether our approach yielded reliable estimates of disease prevalence and of the effects of disease on survival and fecundity rates for treatments of single infections and coinfection. We found two conditions are necessary for reliable estimation. First, diseases must drive detectable changes in vital rates, and second, there must be substantial variation in the degree of prevalence over time. This approach could prove useful for detecting epidemics from public health data in regions where standard surveillance techniques are not available, and in the study of epidemics in wildlife populations, where longitudinal studies can be especially difficult to implement.

scholarly journals Distinguishing within from between individual effects: How to use the within-individual centering method for quadratic pattern

2020 ◽  
Author(s):  
Rémi Fay ◽  
Julien Martin ◽  
Floriane Plard
Keyword(s):  
Linear Relationship ◽  
General Equation ◽  
Evolutionary Dynamics ◽  
Population Level ◽  
List Type ◽  
Ecological Processes ◽  
Individual Pattern ◽  
Individual Effects ◽  
Non Linear ◽  
The Individual

AbstractAny average pattern observed at the population level may confound two different processes: the within-individual process and the between-individual process. Separating within- from between-individual patterns is critical for our understanding of ecological processes and evolutionary dynamics.The within-individual centering method allows distinguishing within from between individual effects and this method has been largely used in ecology to investigate both linear and quadratic patterns. Here we show that two alternative equations could be used for the investigation of quadratic relationships and explain in which circumstances they are valid.We show that these two alternative equations make different assumptions about the shape of the individual pattern. Reviewing the literature, we find that the inappropriate equation has likely been applied by most of the studies investigated quadratic patterns.To investigate properly quadratic patterns using the within individual centering method, it is critical that the pattern assumed by the equation used is consistent with the biological pattern investigated. We illustrate this statement with the example of age-specific trajectories because age corresponds to the most frequent individual-centered variable used for quadratic pattern. Finally, we give the general equation of the within-individual centering method for any non-linear relationship.

scholarly journals CO<sub>2</sub> and nutrient-driven changes across multiple levels of organization in <i>Zostera noltii</i> ecosystems

2014 ◽  
Vol 11 (24) ◽  
pp. 7237-7249 ◽  
Author(s):  
B. Martínez-Crego ◽  
I. Olivé ◽  
R. Santos
Keyword(s):  
Carbon Storage ◽  
Population Level ◽  
Interactive Effects ◽  
Zostera Noltii ◽  
Seagrass Meadows ◽  
Plant Biochemistry ◽  
Individual Effects ◽  
High Nutrient ◽  
The Individual ◽  
Shoot Mortality

Abstract. Increasing evidence emphasizes that the effects of human impacts on ecosystems must be investigated using designs that incorporate the responses across levels of biological organization as well as the effects of multiple stressors. Here we implemented a mesocosm experiment to investigate how the individual and interactive effects of CO2 enrichment and eutrophication scale-up from changes in primary producers at the individual (biochemistry) or population level (production, reproduction, and/or abundance) to higher levels of community (macroalgae abundance, herbivory, and global metabolism), and ecosystem organization (detritus release and carbon sink capacity). The responses of Zostera noltii seagrass meadows growing in low- and high-nutrient field conditions were compared. In both meadows, the expected CO2 benefits on Z. noltii leaf production were suppressed by epiphyte overgrowth, with no direct CO2 effect on plant biochemistry or population-level traits. Multi-level meadow response to nutrients was faster and stronger than to CO2. Nutrient enrichment promoted the nutritional quality of Z. noltii (high N, low C : N and phenolics), the growth of epiphytic pennate diatoms and purple bacteria, and shoot mortality. In the low-nutrient meadow, individual effects of CO2 and nutrients separately resulted in reduced carbon storage in the sediment, probably due to enhanced microbial degradation of more labile organic matter. These changes, however, had no effect on herbivory or on community metabolism. Interestingly, individual effects of CO2 or nutrient addition on epiphytes, shoot mortality, and carbon storage were attenuated when nutrients and CO2 acted simultaneously. This suggests CO2-induced benefits on eutrophic meadows. In the high-nutrient meadow, a striking shoot decline caused by amphipod overgrazing masked the response to CO2 and nutrient additions. Our results reveal that under future scenarios of CO2, the responses of seagrass ecosystems will be complex and context-dependent, being mediated by epiphyte overgrowth rather than by direct effects on plant biochemistry. Overall, we found that the responses of seagrass meadows to individual and interactive effects of CO2 and nutrient enrichment varied depending on interactions among species and connections between organization levels.

scholarly journals Century-long cod otolith biochronology reveals individual growth plasticity in response to temperature

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Szymon Smoliński ◽  
Julie Deplanque-Lasserre ◽  
Einar Hjörleifsson ◽  
Audrey J. Geffen ◽  
Jane A. Godiksen ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Environmental Variability ◽  
Atlantic Cod ◽  
Population Level ◽  
Climatic Conditions ◽  
Individual Growth ◽  
Individual Level ◽  
Thermal Plasticity ◽  
Individual Effects ◽  
The Individual

Abstract Otolith biochronologies combine growth records from individual fish to produce long-term growth sequences, which can help to disentangle individual from population-level responses to environmental variability. This study assessed individual thermal plasticity of Atlantic cod (Gadus morhua) growth in Icelandic waters based on measurements of otolith increments. We applied linear mixed-effects models and developed a century-long growth biochronology (1908–2014). We demonstrated interannual and cohort-specific changes in the growth of Icelandic cod over the last century which were mainly driven by temperature variation. Temperature had contrasting relationships with growth—positive for the fish during the youngest ages and negative during the oldest ages. We decomposed the effects of temperature on growth observed at the population level into within-individual effects and among‐individual effects and detected significant individual variation in the thermal plasticity of growth. Variance in the individual plasticity differed across cohorts and may be related to the mean environmental conditions experienced by the group. Our results underscore the complexity of the relationships between climatic conditions and the growth of fish at both the population and individual level, and highlight the need to distinguish between average population responses and growth plasticity of the individuals for accurate growth predictions.

scholarly journals A methodological framework to predict the individual and population‐level distributions from tracking data

Ecography ◽  
2021 ◽  
Author(s):  
Philippine Chambault ◽  
Tarek Hattab ◽  
Pascal Mouquet ◽  
Touria Bajjouk ◽  
Claire Jean ◽  
...  
Keyword(s):  
Population Level ◽  
Tracking Data ◽  
Methodological Framework ◽  
The Individual

ALTERNATIVE ROUTES TO INNOVATION — THE EFFECTS OF CULTURAL AND STRUCTURAL FIT

2019 ◽  
Vol 24 (01) ◽  
pp. 2050006
Author(s):  
DAG INGVAR JACOBSEN ◽  
TORE HILLESTAD ◽  
BIRGITTE YTTRI ◽  
JARLE HILDRUM
Keyword(s):  
Response Rate ◽  
Organic Structure ◽  
Configurational Approach ◽  
Culture Strength ◽  
Individual Effects ◽  
Collective Phenomenon ◽  
The Individual ◽  
Alternative Routes ◽  
Innovative Culture ◽  
The Empirical Analysis

A configurational approach to organizations assumes that structural and cultural characteristics must be in “fit” to produce the wanted outcome. With a focus on innovation, this study examines empirically to what extent innovative activities with a large, global telecom company are produced by an innovative culture, an innovative structure, as well as the fit between the two. Based on an extensive survey (N = 21064, response rate = 65) of employees in seven countries in Europe and Asia, data was aggregated to unit level as culture by nature is a collective phenomenon. The empirical analysis detected both the individual effects of culture strength and homogeneity, structure, as well as the fit between the two. The results indicate that an innovative culture and an organic structure indeed fosters innovation, but that, somewhat surprisingly, there are not effects of the fit between the two. Both practical and theoretical implications are discussed.

Factors influencing the individual effects of blood transfusions on oxygen delivery and oxygen consumption*

2001 ◽  
Vol 29 (Supplement) ◽  
pp. S173-S179 ◽  
Author(s):  
Mattias Casutt ◽  
Burkhardt Seifert ◽  
Thomas Pasch ◽  
Edith R. Schmid ◽  
Marko I. Turina ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Delivery ◽  
Blood Transfusions ◽  
Factors Influencing ◽  
Individual Effects ◽  
The Individual

scholarly journals Phenotypic plasticity of labile traits in the wild

2013 ◽  
Vol 59 (4) ◽  
pp. 485-505 ◽  
Author(s):  
Jon E. Brommer
Keyword(s):  
Life History ◽  
Phenotypic Plasticity ◽  
Statistical Approach ◽  
Scale Up ◽  
Population Level ◽  
Wild Populations ◽  
Quantitative Genetic ◽  
In The Wild ◽  
The Individual ◽  
Quantitative Genetic Parameters

Abstract Individual-based studies allow quantification of phenotypic plasticity in behavioural, life-history and other labile traits. The study of phenotypic plasticity in the wild can shed new light on the ultimate objectives (1) whether plasticity itself can evolve or is constrained by its genetic architecture, and (2) whether plasticity is associated to other traits, including fitness (selection). I describe the main statistical approach for how repeated records of individuals and a description of the environment (E) allow quantification of variation in plasticity across individuals (IxE) and genotypes (GxE) in wild populations. Based on a literature review of life-history and behavioural studies on plasticity in the wild, I discuss the present state of the two objectives listed above. Few studies have quantified GxE of labile traits in wild populations, and it is likely that power to detect statistically significant GxE is lacking. Apart from the issue of whether it is heritable, plasticity tends to correlate with average trait expression (not fully supported by the few genetic estimates available) and may thus be evolutionary constrained in this way. Individual-specific estimates of plasticity tend to be related to other traits of the individual (including fitness), but these analyses may be anti-conservative because they predominantly concern stats-on-stats. Despite the increased interest in plasticity in wild populations, the putative lack of power to detect GxE in such populations hinders achieving general insights. I discuss possible steps to invigorate the field by moving away from simply testing for presence of GxE to analyses that ‘scale up’ to population level processes and by the development of new behavioural theory to identify quantitative genetic parameters which can be estimated.

scholarly journals Influence of process variables on release properties of paracetamol tablets

2007 ◽  
Vol 57 (1) ◽  
pp. 73-86 ◽  
Author(s):  
Gbenga Alebiowu ◽  
Oludele Itiola
Keyword(s):  
Interaction Effects ◽  
Process Variables ◽  
Factorial Experimental Design ◽  
Disintegration Time ◽  
Individual Effects ◽  
Pregelatinized Starch ◽  
Tablet Formulations ◽  
Binder Concentration ◽  
The Individual ◽  
Paracetamol Tablet

Influence of process variables on release properties of paracetamol tablets A 23 factorial experimental design has been used to quantitatively study individual and interaction effects of the nature of binder (N), binder concentration (c) and relative density of tablet (d) on the disintegration time (DT) and dissolution times, t1, t50 and t90, of paracetamol tablet formulations. The factorial design was also used to study the quantitative effects of pregelatinization of starch binders on these parameters, i.e., N, c and d. In general, the most common ranking of the individual effects on DT, t1, t50 and t90 for native/native, pregelatinized/pregelatinized and native/pregelatinized starch binder formulations was c > d > N. For interaction effects, the most common ranking was N-c > c-d > N-d for all formulations. The results generally showed that c can considerably affect DT, t1, t50 and t90 of the tablets.

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