scholarly journals Heterotrophic eukaryotes show a slow-fast continuum, not a gleaner–exploiter trade-off

2020 ◽  
Vol 117 (40) ◽  
pp. 24893-24899
Author(s):  
Thomas Kiørboe ◽  
Mridul K. Thomas
Keyword(s):  
Positive Relationship ◽  
Ingestion Rate ◽  
Negative Relationship ◽  
Large Mammals ◽  
Ecological Processes ◽  
Trade Off ◽  
Trade Offs ◽  
Wide Range ◽  
Fast Gradient ◽  
Using Data

Gleaners and exploiters (opportunists) are organisms adapted to feeding in nutritionally poor and rich environments, respectively. A trade-off between these two strategies—a negative relationship between the rate at which organisms can acquire food and ingest it—is a critical assumption in many ecological models. Here, we evaluate evidence for this trade-off across a wide range of heterotrophic eukaryotes from unicellular nanoflagellates to large mammals belonging to both aquatic and terrestrial realms. Using data on the resource acquisition and ingestion rates in >500 species, we find no evidence of a trade-off across species. Instead, there is a positive relationship between maximum clearance rate and maximum ingestion rate. The positive relationship is not a result of lumping together diverse taxa; it holds within all subgroups of organisms we examined as well. Correcting for differences in body mass weakens but does not reverse the positive relationship, so this is not an artifact of size scaling either. Instead, this positive relationship represents a slow–fast gradient in the “pace of life” that overrides the expected gleaner–exploiter trade-off. Other trade-offs must therefore shape ecological processes, and investigating them may provide deeper insights into coexistence, competitive dynamics, and biodiversity patterns in nature. A plausible target for study is the well-documented trade-off between growth rate and predation avoidance, which can also drive the slow–fast gradient we observe here.

scholarly journals Robust estimation of vertical symmetry axis models via joint migration inversion: Including multiples in anisotropic parameter estimation

Geophysics ◽  
2019 ◽  
Vol 84 (1) ◽  
pp. C57-C74 ◽  
Author(s):  
Abdulrahman A. Alshuhail ◽  
Dirk J. Verschuur
Keyword(s):  
Symmetry Axis ◽  
Transverse Isotropy ◽  
Half Cycle ◽  
Anisotropic Parameter ◽  
Data Set ◽  
Trade Off ◽  
Trade Offs ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Internal Multiples

Because the earth is predominately anisotropic, the anisotropy of the medium needs to be included in seismic imaging to avoid mispositioning of reflectors and unfocused images. Deriving accurate anisotropic velocities from the seismic reflection measurements is a highly nonlinear and ambiguous process. To mitigate the nonlinearity and trade-offs between parameters, we have included anisotropy in the so-called joint migration inversion (JMI) method, in which we limit ourselves to the case of transverse isotropy with a vertical symmetry axis. The JMI method is based on strictly separating the scattering effects in the data from the propagation effects. The scattering information is encoded in the reflectivity operators, whereas the phase information is encoded in the propagation operators. This strict separation enables the method to be more robust, in that it can appropriately handle a wide range of starting models, even when the differences in traveltimes are more than a half cycle away. The method also uses internal multiples in estimating reflectivities and anisotropic velocities. Including internal multiples in inversion not only reduces the crosstalk in the final image, but it can also reduce the trade-off between the anisotropic parameters because internal multiples usually have more of an imprint of the subsurface parameters compared with primaries. The inverse problem is parameterized in terms of a reflectivity, vertical velocity, horizontal velocity, and a fixed [Formula: see text] value. The method is demonstrated on several synthetic models and a marine data set from the North Sea. Our results indicate that using JMI for anisotropic inversion makes the inversion robust in terms of using highly erroneous initial models. Moreover, internal multiples can contain valuable information on the subsurface parameters, which can help to reduce the trade-off between anisotropic parameters in inversion.

Relationship Quality Among Older Cohabitors: A Comparison to Remarrieds

2019 ◽  
Vol 75 (8) ◽  
pp. 1808-1817
Author(s):  
Matthew R Wright
Keyword(s):  
Relationship Quality ◽  
Positive Relationship ◽  
Negative Relationship ◽  
Later Life ◽  
Well Being ◽  
Poor Quality ◽  
Two Measures ◽  
Using Data ◽  
Union Type ◽  
Quality Relationships

Abstract Objectives Later life marital patterns have undergone shifts over the past few decades, including a rapid growth of cohabiting unions. Despite the increase in older adult cohabitation, research on this population has been slow to keep up. Intimate relationships are linked to well-being and relationship quality is especially important because high-quality relationships offer a number of benefits for well-being, whereas poor-quality relationships often are detrimental. This study compares cohabiting and remarried individuals on two measures of relationship quality. Method Using data from the 2010 and 2012 Health and Retirement Study, I investigate the positive and negative relationship quality of cohabitors relative to their remarried counterparts and whether the association of union type and relationship quality varies by race. Results Across both positive and negative relationship quality, I found few differences between cohabiting and remarried individuals. Black cohabitors report higher positive relationship quality than remarrieds, whereas White cohabitors and remarrieds do not differ. Discussion These findings suggest that cohabiting unions and remarriages are comparable among White older adults, but that Black cohabitors may gain more in terms of positive relationship quality than their remarried counterparts.

scholarly journals Heat hardening in a pair of Anolis lizards: constraints, dynamics, and ecological consequences

2021 ◽  
pp. jeb.240994
Author(s):  
Sean W. Deery ◽  
Julie E. Rej ◽  
Daniel Haro ◽  
Alex. R. Gunderson
Keyword(s):  
Heat Shock ◽  
Heat Tolerance ◽  
Negative Relationship ◽  
Anolis Carolinensis ◽  
Biophysical Model ◽  
Published Data ◽  
Lizard Species ◽  
Trade Off ◽  
Trade Offs ◽  
Heat Hardening

Heat tolerance plasticity is predicted to be an important buffer against global warming. Nonetheless, basal heat tolerance often correlates negatively with tolerance plasticity (“Trade-off Hypothesis”), a constraint that could limit plasticity benefits. We tested the trade-off hypothesis at the individual level with respect to heat hardening in two lizard species, Anolis carolinensis and A. sagrei. Heat hardening is a rapid increase in heat tolerance after heat shock that is rarely measured in reptiles but is generally considered a first line of physiological defense against heat. We also employed a biophysical model of operative habitat temperatures to estimate the performance consequences of hardening under ecologically relevant conditions. Anolis carolinensis hardened by two hours post heat shock and maintained hardening for several hours. However, A. sagrei did not harden. Biophysical models showed that hardening in A. carolinensis reduces their overheating risk in the field. Therefore, while not all lizards heat harden, hardening has benefits for species that can. We initially found a negative relationship between basal tolerance and hardening within both species, consistent with the trade-off hypothesis. However, permutation analyses showed that the apparent trade-offs could not be differentiated from statistical artifact. We found the same result when we re-analyzed published data supporting the trade-off hypothesis in another lizard species. Our results show that false positives may be common when testing the trade-off hypothesis. Statistical approaches that account for this are critical to ensure that the hypothesis, which has broad implications for thermal adaptation and responses to warming, is assessed appropriately.

An integrated methodology to assess the operational and environmental performance of a conceptual regenerative helicopter

2015 ◽  
Vol 119 (1211) ◽  
pp. 67-90 ◽  
Author(s):  
F. Ali ◽  
I. Goulos ◽  
V. Pachidis
Keyword(s):  
Environmental Impact ◽  
Environmental Performance ◽  
Engine Performance ◽  
Comprehensive Assessment ◽  
Operational Performance ◽  
Reactor Model ◽  
Trade Off ◽  
Emissions Inventory ◽  
Trade Offs ◽  
Wide Range

AbstractThis paper aims to present an integrated multidisciplinary simulation framework, deployed for the comprehensive assessment of combined helicopter–powerplant systems at mission level. Analytical evaluations of existing and conceptual regenerative engine designs are carried out in terms of operational performance and environmental impact. The proposed methodology comprises a wide-range of individual modeling theories applicable to helicopter flight dynamics, gas turbine engine performance as well as a novel, physics-based, stirred reactor model for the rapid estimation of various helicopter emissions species. The overall methodology has been deployed to conduct a preliminary trade-off study for a reference simple cycle and conceptual regenerative twin-engine light helicopter, modeled after the Airbus Helicopters Bo105 configuration, simulated under the representative mission scenarios. Extensive comparisons are carried out and presented for the aforementioned helicopters at both engine and mission level, along with general flight performance charts including the payload-range diagram. The acquired results from the design trade-off study suggest that the conceptual regenerative helicopter can offer significant improvement in the payload-range capability, while simultaneously maintaining the required airworthiness requirements. Furthermore, it has been quantified through the implementation of a representative case study that, while the regenerative configuration can enhance the mission range and payload capabilities of the helicopter, it may have a detrimental effect on the mission emissions inventory, specifically for NOx(Nitrogen Oxides). This may impose a trade-off between the fuel economy and environmental performance of the helicopter. The proposed methodology can effectively be regarded as an enabling technology for the comprehensive assessment of conventional and conceptual helicopter-powerplant systems, in terms of operational performance and environmental impact as well as towards the quantification of their associated trade-offs at mission level.

When Civilians Are Attacked: Gender Equality and Terrorist Targeting

2019 ◽  
Vol 63 (10) ◽  
pp. 2289-2318 ◽  
Author(s):  
Laura Huber
Keyword(s):  
Public Opinion ◽  
Gender Equality ◽  
Negative Relationship ◽  
Domestic Terrorism ◽  
Trade Off ◽  
Peace And Security ◽  
Using Data ◽  
Public Reaction ◽  
Gender Quota

While scholars demonstrate a consistent negative relationship between gender equality and violence, the effect of women’s rights on the quality of terrorism and the type of victims targeted remains unexplored. This article introduces a new model of terrorists’ strategic targeting by examining the trade-off between the ease of a civilian-oriented attack and the negative public reaction these attacks invoke. Within this framework, gender equality increases the costs of civilian targeting by inducing public opinion costs. As gender equality increases, the costs of attacking civilians increase relatively more than government-oriented attacks. Using data on domestic terrorism between 1970 and 2007 and a subnational examination of a randomly implemented gender quota in India, this study demonstrates that as gender equality increases, the ratio of civilian-oriented to government-oriented attacks decreases. Overall, this study refines our understanding of terrorists’ strategic targeting and identifies heterogeneity in the Women, Peace, and Security theory.

scholarly journals Consistency of demographic trade-offs across tropical forests

2021 ◽  
Author(s):  
Stephan Kambach ◽  
Richard Condit ◽  
Salomón Aguilar ◽  
Helge Bruelheide ◽  
Sarayudh Bunyavejchewin ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Tropical Forests ◽  
Large Scale ◽  
Negative Relationship ◽  
Trade Off ◽  
Growth And Survival ◽  
Trade Offs ◽  
Tree Communities ◽  
Demographic Processes ◽  
Tropical Forest Dynamics

All species must balance their allocation to growth, survival and recruitment. Among trees, evolution has resulted in different strategies of partitioning resources to these key demographic processes, i.e. demographic trade-offs. It is unclear whether the same demographic trade-offs structure tropical forests worldwide. Here, we used data from 13 large-scale and long-term tropical forest plots to estimate the principal trade-offs in growth, survival, recruitment, and tree stature at each site. For ten sites, two trade-offs appeared repeatedly. One trade-off showed a negative relationship between growth and survival, i.e. the well-known fast−slow continuum. The second trade-off distinguished between tall-statured species and species with high recruitment rates, i.e. a stature−recruitment trade-off. Thus, the fast-slow continuum and tree stature are two independent dimensions structuring most tropical tree communities. Our discovery of the consistency of demographic trade-offs and strategies across forest types in three continents substantially improves our ability to predict tropical forest dynamics worldwide.

scholarly journals Cost of resistance: an unreasonably expensive concept

2018 ◽  
Vol 3 ◽  
pp. 51-70 ◽  
Author(s):  
Thomas Lenormand ◽  
Noémie Harmand ◽  
Romain Gallet
Keyword(s):  
Pleiotropic Effects ◽  
Adaptation Theory ◽  
Trade Off ◽  
Resistance Evolution ◽  
Fitness Effects ◽  
Trade Offs ◽  
Wide Range ◽  
Recent Developments ◽  
Cost Of Resistance ◽  
Genetics And Genomics

The concept of “cost of resistance” has been very important for decades, for fundamental reasons (theory of adaptation), with a wide range of applications for the genetics and genomics of resistance: resistance to antibiotics, insecticide, herbicide, fungicides; resistance to chemotherapy in cancer research; coevolution between all kinds of parasites and their hosts. This paper reviews this history, including latest developments, shows the interest of the idea but also challenges the usefulness and limits of this widely used concept, based on the most recent development of adaptation theory.  It explains how the concept can be flawed and how this can impede research efforts in the field of resistance at large, including all applied aspects. In particular, it would be clearer to simply measure the fitness effects of mutations across environments and to better distinguish those effects from ‘pleiotropic effects’ of those mutations. Overall, we show how to correct the concept, and how this correction helps to better understand the wealth of data that has accumulated in recent years. The main points are: 1. The concept of «cost of resistance» needs to be carefully used, to avoid misconceptions, false paradox and flawed applications. The recent developments in adaptation theory are useful to clarify this. 2. “Cost of resistance” and pleiotropy have to be distinguished. More than one trait is required to discuss pleiotropy. Resistance evolution must at least involve the modification of one trait. If there is an irreducible trade-off on that trait between environments with and without drug, it creates a fitness effect that is not due to pleiotropy. Pleiotropic effects can, but need not, occur in addition. 3. “Cost of resistance” must depend on the pair of environments considered with and without drug. Hence, there are as many measures of cost as there are environments without drug. If the focal genotype is not well adapted to one focal environment, it is relatively easy to observe “negative” costs of resistance. There is nothing surprising about this, and it does not indicate an absence of trade-off. 4. Environments with drug can differ according to the dose. It may be more informative to measure the possible trade-offs among all doses than to focus exclusively on the fitness contrast between the presence and the absence of drug.

scholarly journals Anomalous invasion dynamics due to dispersal polymorphism and dispersal-reproduction trade-offs

2020 ◽  
Author(s):  
Vincent A. Keenan ◽  
Stephen J. Cornell
Keyword(s):  
Life History Theory ◽  
Invasion Speed ◽  
Complex Behaviour ◽  
Trade Off ◽  
Invasion Dynamics ◽  
Population Growth Rates ◽  
Trade Offs ◽  
Invasion Fronts ◽  
Wide Range ◽  
Dispersal Polymorphism

AbstractDispersal polymorphism and mutation play significant roles during biological invasions, potentially leading to evolution and complex behaviour such as accelerating or decelerating invasion fronts. However, life history theory predicts that reproductive fitness — another key determinant of invasion dynamics – may be lower for more dispersive strains. Here, we use a mathematical model to show that unexpected invasion dynamics emerge from the combination of heritable dispersal polymorphism, dispersal-fitness trade-offs, and mutation between strains. We show that the invasion dynamics are determined by the trade-off relationship between dispersal and population growth rates of the constituent strains. We find that invasion dynamics can be “anomalous” (i.e. faster than any of the strains in isolation), but that the ultimate invasion speed is determined by the traits of at most two strains. The model is simple but generic, so we expect the predictions to apply to a wide range of ecological, evolutionary or epidemiological invasions.

scholarly journals Conflicting functional effects of xylem pit structure relate to the growth-longevity trade-off in a conifer species

2019 ◽  
Vol 116 (30) ◽  
pp. 15282-15287 ◽  
Author(s):  
Beth Roskilly ◽  
Eric Keeling ◽  
Sharon Hood ◽  
Arnaud Giuggiola ◽  
Anna Sala
Keyword(s):  
Life History ◽  
Pinus Ponderosa ◽  
Growth Rates ◽  
Morphological Traits ◽  
Natural Populations ◽  
Negative Relationship ◽  
Multiple Traits ◽  
Conifer Species ◽  
Trade Off ◽  
Trade Offs

Consistent with a ubiquitous life history trade-off, trees exhibit a negative relationship between growth and longevity both among and within species. However, the mechanistic basis of this life history trade-off is not well understood. In addition to resource allocation conflicts among multiple traits, functional conflicts arising from individual morphological traits may also contribute to life history trade-offs. We hypothesized that conflicting functional effects of xylem structural traits contribute to the growth-longevity trade-off in trees. We tested this hypothesis by examining the extent to which xylem morphological traits (i.e., wood density, tracheid diameters, and pit structure) relate to growth rates and longevity in two natural populations of the conifer speciesPinus ponderosa. Hydraulic constraints arise as trees grow larger and xylem anatomical traits adjust to compensate. We disentangled the effects of size through ontogeny in individual trees and growth rates among trees on xylem traits by sampling each tree at multiple trunk diameters. We found that the oldest trees had slower lifetime growth rates compared with younger trees in the studied populations, indicating a growth-longevity trade-off. We further provide evidence that a single xylem trait, pit structure, with conflicting effects on xylem function (hydraulic safety and efficiency) relates to the growth-longevity trade-off in a conifer species. This study highlights that, in addition to trade-offs among multiple traits, functional constraints based on individual morphological traits like that of pit structure provide mechanistic insight into how and when life history trade-offs arise.

scholarly journals Testing relationships between firm size and perceptions of growth and profitability: An investigation into the practices of Australian ICT SMEs

2016 ◽  
Vol 22 (5) ◽  
pp. 680-701 ◽  
Author(s):  
Áron Perényi ◽  
Andrey Yukhanaev
Keyword(s):  
Firm Size ◽  
Firm Growth ◽  
Positive Relationship ◽  
Empirical Studies ◽  
High Growth ◽  
Entrepreneurial Success ◽  
Resource Based View ◽  
Trade Off ◽  
Trade Offs ◽  
Profit Growth

AbstractGibrat’s Law mandates the independence of firm size and growth, while the resource-based view of the firm implies a positive relationship between firm size and profits, to be concluded in a profit–growth trade-off. Empirical studies of entrepreneurial success however, have demonstrated firms’ ability to reach a state of high growth and profitability, despite the trade-offs encapsulated within the profit–growth nexus. Upon assessing the relationships between past profitability, current firm growth and size in Australian ICT SMEs, results demonstrate positive relationships between all three indicators. This suggests that profitability can be considered the most important precursor of entrepreneurial success, and also that successful businesses do not suffer from the trade-offs implied by theory.

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