scholarly journals Evolutionary determinants of morphological polymorphism in colonial animals

2016 ◽  
Author(s):  
Carl Simpson ◽  
Jeremy B.C. Jackson ◽  
Amalia Herrera-Cubilla
Keyword(s):  
Life Histories ◽  
Competitive Ability ◽  
Environmental Variability ◽  
Temporal Position ◽  
Costs And Benefits ◽  
Isthmus Of Panama ◽  
Modular Units ◽  
Environmental Hypothesis ◽  
Colonial Ascidians

AbstractColonial animals commonly exhibit morphologically polymorphic modular units that are phenotypically distinct and specialize in specific functional tasks. But how and why these polymorphic modules have evolved is poorly understood. Across colonial invertebrates there is wide variation in the degree of polymorphism from none in colonial ascidians, to extreme polymorphism in siphonophores such as the Portuguese Man of War. Bryozoa are a phylum of exclusively colonial invertebrates that uniquely exhibit almost the entire range of polymorphism from monomorphic species to others that rival siphonophores in their polymorphic complexity. Previous approaches to understanding the evolution of polymorphism have been based upon analyses of (1) the functional role of polymorphs or (2) presumed evolutionary costs and benefits based upon evolutionary theory that postulates polymorphism should only be evolutionarily sustainable in more “stable” environments because polymorphism commonly leads to the loss of feeding and sexual competence. Here we use bryozoans from opposite shores of the Isthmus of Panama to revisit the environmental hypothesis by comparison of faunas from distinct oceanographic provinces that differ greatly in environmental variability and we then examine the correlations between the extent of polymorphism in relation to patterns of ecological succession and variation in life histories. We find no support for the environmental hypothesis. Distributions of the incidence of polymorphism in the oceanographically unstable Eastern Pacific are indistinguishable from those in the more stable Caribbean. In contrast, the temporal position of species in a successional sequence is collinear with the degree of polymorphism because species with fewer types of polymorphs are competitively replaced by species with higher numbers of polymorphs on the same substrata. Competitively dominant species also exhibit patterns of growth that increase their competitive ability. The association between degrees of polymorphism and variations in life histories is fundamental to understanding of the macroevolution of polymorphism.

Hostile Takeovers and Anti-takeover Defenses in the Russian Corporate Market

2007 ◽  
pp. 70-84 ◽  
Author(s):  
E. Demidova
Keyword(s):  
Cost Benefit Analysis ◽  
Cost Benefit ◽  
Benefit Analysis ◽  
Costs And Benefits ◽  
Hostile Takeovers ◽  
Russian Market ◽  
Takeover Defenses ◽  
The Cost ◽  
European Markets

This article analyzes definitions and the role of hostile takeovers at the Russian and European markets for corporate control. It develops the methodology of assessing the efficiency of anti-takeover defenses adapted to the conditions of the Russian market. The paper uses the cost-benefit analysis, where the costs and benefits of the pre-bid and post-bid defenses are compared.

The Ethics of Petroleum

2017 ◽  
Author(s):  
Jonathon W. Moses ◽  
Bjørn Letnes
Keyword(s):  
Corporate Social Responsibility ◽  
Social Responsibility ◽  
Host Country ◽  
Corporate Citizenship ◽  
Costs And Benefits ◽  
Political Actors ◽  
Oil Companies ◽  
Corporate Social ◽  
Oil Company

This chapter considers the role of international oil companies (IOCs) as global political actors with significant economic and political power. In doing so, we weigh the ethical costs and benefits for individuals, companies, and states alike. Using the concepts of “corporate social responsibility” (CSR) and “corporate citizenship” as points of departure, we consider the extent to which international oil companies have social and political responsibilities in the countries where they operate and what the host country can do to encourage this sort of behavior. We examine the nature of anticorruption legislation in several of the sending countries (including Norway), and look closely at how the Norwegian national oil company (NOC), Statoil, has navigated these ethical waters.

The Acceptance of Party Unity in Parliamentary Democracies

2017 ◽  
Author(s):  
David M. Willumsen
Keyword(s):  
Political Parties ◽  
Costs And Benefits ◽  
Parliamentary Democracies ◽  
Survey Questions ◽  
Ideal Policy ◽  
Central Argument ◽  
The Individual ◽  
Policy Incentives

The central argument of this book is that voting unity in European legislatures is not primarily the result of the ‘disciplining’ power of the leadership of parliamentary parties, but rather the result of a combination of ideological homogeneity through self-selection into political parties and the calculations of individual legislators about their own long-term benefits. Despite the central role of policy preferences in the subsequent behaviour of legislators, preferences at the level of the individual legislator have been almost entirely neglected in the study of parliaments and legislative behaviour. The book measures these using an until now under-utilized resource: parliamentary surveys. Building on these, the book develops measures of policy incentives of legislators to dissent from their parliamentary parties, and show that preference similarity amongst legislators explains a very substantial proportion of party unity, yet alone cannot explain all of it. Analysing the attitudes of legislators to the demands of party unity, and what drives these attitudes, the book argues that what explains the observed unity (beyond what preference similarity would explain) is the conscious acceptance by MPs that the long-term benefits of belonging to a united party (such as increased influence on legislation, lower transaction costs, and better chances of gaining office) outweigh the short-terms benefits of always voting for their ideal policy outcome. The book buttresses this argument through the analysis of both open-ended survey questions as well as survey questions on the costs and benefits of belonging to a political party in a legislature.

Hormones and Behavior

2019 ◽  
pp. 11-26
Author(s):  
Maren N. Vitousek ◽  
Laura A. Schoenle
Keyword(s):  
Life History ◽  
Life Histories ◽  
Life History Traits ◽  
Developmental Plasticity ◽  
Endocrine System ◽  
Phenotypic Traits ◽  
Social Environments ◽  
Trade Offs ◽  
And Behavior

Hormones mediate the expression of life history traits—phenotypic traits that contribute to lifetime fitness (i.e., reproductive timing, growth rate, number and size of offspring). The endocrine system shapes phenotype by organizing tissues during developmental periods and by activating changes in behavior, physiology, and morphology in response to varying physical and social environments. Because hormones can simultaneously regulate many traits (hormonal pleiotropy), they are important mediators of life history trade-offs among growth, reproduction, and survival. This chapter reviews the role of hormones in shaping life histories with an emphasis on developmental plasticity and reversible flexibility in endocrine and life history traits. It also discusses the advantages of studying hormone–behavior interactions from an evolutionary perspective. Recent research in evolutionary endocrinology has provided insight into the heritability of endocrine traits, how selection on hormone systems may influence the evolution of life histories, and the role of hormonal pleiotropy in driving or constraining evolution.

scholarly journals Robustness of life histories to environmental variability in complex versus simple life cycles

2021 ◽  
Author(s):  
Annie Jonsson
Keyword(s):  
Growth Rate ◽  
Life Histories ◽  
Environmental Variability ◽  
Life Cycles ◽  
Relative Advantage ◽  
Complex Life Cycle ◽  
Life Stages ◽  
Vital Rates ◽  
Habitat Separation ◽  
Simple Life

AbstractMost animal species have a complex life cycle (CLC) with metamorphosis. It is thus of interest to examine possible benefits of such life histories. The prevailing view is that CLC represents an adaptation for genetic decoupling of juvenile and adult traits, thereby allowing life stages to respond independently to different selective forces. Here I propose an additional potential advantage of CLCs that is, decreased variance in population growth rate due to habitat separation of life stages. Habitat separation of pre- and post-metamorphic stages means that the stages will experience different regimes of environmental variability. This is in contrast to species with simple life cycles (SLC) whose life stages often occupy one and the same habitat. The correlation in the fluctuations of the vital rates of life stages is therefore likely to be weaker in complex than in simple life cycles. By a theoretical framework using an analytical approach, I have (1) derived the relative advantage, in terms of long-run growth rate, of CLC over SLC phenotypes for a broad spectrum of life histories, and (2) explored which life histories that benefit most by a CLC, that is avoid correlation in vital rates between life stages. The direction and magnitude of gain depended on life history type and fluctuating vital rate. One implication of our study is that species with CLCs should, on average, be more robust to increased environmental variability caused by global warming than species with SLCs.

Vertical Trade Relationships: The Role of Dependence and Symmetry in Attaining Organizational Goals

1992 ◽  
Vol 29 (1) ◽  
pp. 65-75 ◽  
Author(s):  
Lauranne Buchanan
Keyword(s):  
Performance Goals ◽  
Costs And Benefits ◽  
Strong Ties ◽  
Organizational Goals ◽  
Vertical Trade ◽  
Trade Relationships ◽  
The Impact ◽  
Trade Partners

The perspective that dependence on vertical trade partners should be avoided has been countered recently by the view that there are advantages to strong ties between firms. The author offers a framework from which trade partners can assess the potential costs and benefits of trade relationships and empirically investigates the impact of trade relationships on the firm's ability to realize performance goals.

Costs and benefits of livestock systems and the role of market and nonmarket relationships

2005 ◽  
Vol 32 (2) ◽  
pp. 181-193 ◽  
Author(s):  
Henk A. J. Moll
Keyword(s):  
Costs And Benefits ◽  
Livestock Systems

scholarly journals Evaluating the role of contracting and expanding rainforest in initiating cycles of speciation across the Isthmus of Panama

2012 ◽  
Vol 279 (1742) ◽  
pp. 3520-3526 ◽  
Author(s):  
Brian Tilston Smith ◽  
Amei Amei ◽  
John Klicka
Keyword(s):  
Bird Species ◽  
Tropical Regions ◽  
Isthmus Of Panama ◽  
Species Pairs ◽  
The Matrix ◽  
High Species Richness ◽  
The Rich ◽  
The Tropics ◽  
The Impact

Climatic and geological changes across time are presumed to have shaped the rich biodiversity of tropical regions. However, the impact climatic drying and subsequent tropical rainforest contraction had on speciation has been controversial because of inconsistent palaeoecological and genetic data. Despite the strong interest in examining the role of climatic change on speciation in the Neotropics there has been few comparative studies, particularly, those that include non-rainforest taxa. We used bird species that inhabit humid or dry habitats that dispersed across the Panamanian Isthmus to characterize temporal and spatial patterns of speciation across this barrier. Here, we show that these two assemblages of birds exhibit temporally different speciation time patterns that supports multiple cycles of speciation. Evidence for these cycles is further corroborated by the finding that both assemblages consist of ‘young’ and ‘old’ species, despite dry habitat species pairs being geographically more distant than pairs of humid habitat species. The matrix of humid and dry habitats in the tropics not only allows for the maintenance of high species richness, but additionally this study suggests that these environments may have promoted speciation. We conclude that differentially expanding and contracting distributions of dry and humid habitats was probably an important contributor to speciation in the tropics.

scholarly journals Reduced Translocation Is Associated with Tolerance of Common Lambsquarters (Chenopodium album) to Glyphosate

Weed Science ◽  
2013 ◽  
Vol 61 (3) ◽  
pp. 353-360 ◽  
Author(s):  
Melinda K. Yerka ◽  
Andrew T. Wiersma ◽  
R. Bradley Lindenmayer ◽  
Philip Westra ◽  
William G. Johnson ◽  
...  
Keyword(s):  
Competitive Ability ◽  
Chenopodium Album ◽  
Protein Abundance ◽  
Crop Species ◽  
Common Lambsquarters ◽  
Treated Leaf ◽  
The Mean ◽  
Shoot Mass ◽  
Sites Of Action

Common lambsquarters tolerance to glyphosate is problematic because of the species' widespread distribution, competitive ability with many crop species, the widespread use of glyphosate in agriculture, and the weed's potential to develop decreased sensitivity to multiple herbicide sites of action. The mechanism that confers common lambsquarters tolerance to glyphosate is not known. Therefore, we conducted experiments to determine the mechanism of tolerance to glyphosate in an accession of common lambsquarters from Indiana relative to a sensitive accession from Wisconsin. The ED50(the effective dose that reduced shoot mass 50% relative to nontreated plants) value for the tolerant accession (1.6 kg ae ha−1± 0.4 standard error of the mean [SEM]) was eightfold greater than the ED50for the sensitive accession (0.2 kg ae ha−1± 0.2 SEM) 28 d after treatment. The glyphosate target-site (EPSPS) DNA sequence at proline 106, shikimate accumulation as an estimate of EPSPS sensitivity, and EPSPS protein abundance did not differ between accessions. Absorption of14C-glyphosate was slightly greater in the tolerant accession than it was in the sensitive accession at 48 and 72 h after treatment (HAT). However, the tolerant accession translocated a smaller percentage of absorbed14C-glyphosate to the tissue above the treated leaf, which included the shoot apical meristem, at 24, 48, and 72 HAT (P ≤ 0.05, 0.01, and 0.10, respectively). These results suggest an important role of reduced translocation in conferring tolerance of common lambsquarters to glyphosate.

“Knowledge-Based Economics” in the Innovative Development of the Construction Sphere

2015 ◽  
Vol 725-726 ◽  
pp. 996-1001
Author(s):  
Galina Tokunova ◽  
Alexander Petrov
Keyword(s):  
Construction Industry ◽  
Competitive Ability ◽  
Scientific Discipline ◽  
Knowledge Based ◽  
Institutional Structures ◽  
The Usa ◽  
Business Structures ◽  
The Government ◽  
Technological Platforms

The increased role of knowledge in the economics, the growth of the role of education and innovations caused the necessity to revise the role of the basic subjects in the market (the government, business structures, universities) and mechanisms of their interaction. The primary importance is now being shifted towards such subjects of innovations as resource centers, innovative businesses, technological platforms, the clusters capable of exerting efficient influence upon the innovations process, which, in its turn, improves the competitive ability of particular spheres of business and entire national economics. This process also influenced the construction industry. The purpose of this research is to analyze the manifestation of the phenomenon of the knowledge-based economics in the construction sphere. The tasks of this research: firstly, to highlight the evolution of the scientific discipline “knowledge-based economics”; secondly, to analyze the efficiency of the phenomenon on the example of the USA, the EC and Russia; thirdly, to analyze the innovative process in the construction sphere; fourthly, to highlight the role of various institutional structures (resource centers, innovative businesses, technological platforms, clusters) for innovative activity in the construction sphere.

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