The role of selection in the evolution of blindness in cave fish

2020 ◽  
Vol 130 (3) ◽  
pp. 421-432 ◽  
Author(s):  
Horst Wilkens
Keyword(s):  
Neutral Theory ◽  
Genetic Introgression ◽  
Cave Fish ◽  
Surface Form ◽  
Continuous Darkness ◽  
Ongoing Debate ◽  
Dark Pigmentation ◽  
Phenotypic And Genotypic Variability ◽  
Neutral Mutations

Abstract The forces driving regression of biologically functionless traits remain disputed. There is ongoing debate regarding whether selection, as opposed to disuse and neutral mutations, is involved in this process. Cave species are of particular relevance for study in this regard because in continuous darkness all traits that depend on information from light, such as eyes, dark pigmentation and certain behaviours, abruptly lose their function. Recently, strong selection driving reduction has again been proposed, which relied on modelling analyses based on assumptions such as immigration of surface alleles into the cave forms or no fitness difference existing between Astyanax surface and cave fish. The validity of these assumptions, often applied to reject neutral processes in functionless traits, is questioned in this review. Morphological variation in a trait resulting from genetic variability is typical of biologically functionless traits and is particularly notable in phylogenetically young cave species. It is the most evident indicator of loss of selection, which normally enforces uniformity to guarantee optimal functionality. Phenotypic and genotypic variability in Astyanax cave fish eyes does not derive from genetic introgression by the surface form, but from regressive mutations not being eliminated by selection. This matches well with the principles of Kimura’s neutral theory of molecular evolution.

Implications

2017 ◽  
Author(s):  
Mark Edele
Keyword(s):  
Soviet Union ◽  
Second World War ◽  
Soviet Regime ◽  
World War ◽  
Ongoing Debate ◽  
Middle Position ◽  
The Soviet Union ◽  
War Effort ◽  
Second World

This chapter turns to the present and explains the implications of the current study for the ongoing debate about the Soviet Union in the Second World War and in particular about the role of loyalty and disloyalty in the Soviet war effort. It argues that this study strengthens those who argue for a middle position: the majority of Soviet citizens were neither unquestioningly loyal to the Stalinist regime nor convinced resisters. The majority, instead, saw their interests as distinct from both the German and the Soviet regime. Nevertheless, ideology remains important if we want to understand why in the Soviet Union more resisted or collaborated than elsewhere in Europe and Asia.

scholarly journals Entrepreneurial ecosystems: Founding figures and research frontiers in economic geography

2019 ◽  
Vol 63 (2-4) ◽  
pp. 55-63 ◽  
Author(s):  
Susann Schäfer ◽  
Heike Mayer
Keyword(s):  
Economic Geography ◽  
Unique Contribution ◽  
Special Issue ◽  
Entrepreneurial Ecosystem ◽  
Ongoing Debate ◽  
Entrepreneurial Ecosystems ◽  
Published Research ◽  
Research Frontiers

Abstract The editorial for the special issue on entrepreneurial ecosystems summarizes the ongoing debate on the entrepreneurial ecosystem concept and portrays the backgrounds of founding figures of the concept. It traces the unique contribution of this issue with regard to recently published research. The contributions deal with the measurement of and the role of specific actors and institutions in entrepreneurial ecosystems.

scholarly journals The universal force of free choice any

2004 ◽  
Vol 4 ◽  
pp. 5-40 ◽  
Author(s):  
Veneeta Dayal
Keyword(s):  
Free Choice ◽  
Linguistic Variation ◽  
Ongoing Debate ◽  
Existential Statement

This paper adds to the ongoing debate about the quantificational status of English FC any. It argues that any is a universal, though its universality is such that it can be conjoined with an existential statement. This is established by showing, first of all, that various properties that are amenable to a universal account of FC any remain elusive in recent accounts that treat it as an indefinite. Secondly, it presents a detailed description of supplementary/numeral any, cases in which any occurs with an indefinite. Such cases have been assumed to provide evidence for the indefinite-any view but an explicit semantics for the constructions is given, showing that any invariably contributes universal quantificational force. Existential force always comes from other elements. The paper also discusses alternative formulations that preserve the key insights of the universalist position and the role of cross-linguistic variation in the study of FC items.

BLIND MEXICAN CAVE FISH (ASTYANAX HUBBSI) RESPOND TO MOVING VISUAL STIMULI

1994 ◽  
Vol 188 (1) ◽  
pp. 89-101 ◽  
Author(s):  
T Teyke ◽  
S Schaerer
Keyword(s):  
Visual Stimulus ◽  
Swimming Velocity ◽  
Environmental Cues ◽  
Cave Fish ◽  
Optomotor Response ◽  
Aquarium Fish ◽  
Modified Theory ◽  
Test Aquarium ◽  
Optomotor Behaviour

In apparatus for measuring optomotor behaviour, blind Mexican cave fish, Astyanax hubbsi, increase their swimming velocity upon rotation of a striped cylinder, i.e. in response to a solely visual stimulus. The fish follow the movements of the stripes at (i) rotation velocities between 60 degrees s-1 and 80 degrees s-1, (ii) light intensities of less than 20 lx and, (iii) stimulus widths subtending an angle of less than 1 °. Extirpation of the vestigial eye structures does not affect the response to the moving visual stimulus, which indicates that the response is mediated by extra-ocular photoreceptors. An optomotor response can be reliably evoked in a round test aquarium. Fish do not respond when the test aquarium contains environmental cues, such as bars on the wall or when a section of the round aquarium is divided off. This indicates that the fish obtain information about their environment from different sensory sources and that the visual stimulus is effective only when no other means of orientation are available. We suggest a modified theory of the optomotor response, which emphasizes the crucial role of the environment in eliciting the response and which permits behaviours more complex than just following the stimulus.

GENETIC REPRESENTATION AND GENETIC NEUTRALITY IN GENE EXPRESSION PROGRAMMING

2002 ◽  
Vol 05 (04) ◽  
pp. 389-408 ◽  
Author(s):  
CÂNDIDA FERREIRA
Keyword(s):  
Gene Expression ◽  
Molecular Evolution ◽  
Gene Expression Programming ◽  
Neutral Theory ◽  
Artificial System ◽  
Evolutionary Systems ◽  
Theory Of Evolution ◽  
Coding Regions ◽  
Neutral Mutations

The neutral theory of molecular evolution states that the accumulation of neutral mutations in the genome is fundamental for evolution to occur. The genetic representation of gene expression programming, an artificial genotype/phenotype system, not only allows the existence of non-coding regions in the genome where neutral mutations can accumulate but also allows the controlled manipulation of both the number and the extent of these non-coding regions. Therefore, gene expression programming is an ideal artificial system where the neutral theory of evolution can be tested in order to gain some insights into the workings of artificial evolutionary systems. The results presented in this work show beyond any doubt that the existence of neutral regions in the genome is fundamental for evolution to occur efficiently.

Neutrality in the Study of Religion

2022 ◽  
Vol 50 (2) ◽  
pp. 73-76
Author(s):  
John H. Whittaker
Keyword(s):  
Department Chair ◽  
Religious Studies ◽  
State University ◽  
Original Publication ◽  
Critical Inquiry ◽  
Ongoing Debate ◽  
Louisiana State University ◽  
Robert Bellah

The Archive is a feature of the Bulletin in which previous publications are reprinted to reinforce the modern relevance of archived arguments. “Neutrality in the Study of Religion,” originally published in 1981, comes from Dr. John H. Whittaker (1945-2019), who was the Department Chair of Philosophy and Religious Studies at Louisiana State University until 2006. This article is relevant 30 years after its original publication, as it explores an ongoing debate in the field: the limits of objectivity in religious studies. Whittaker critiques a claim made by sociologist Robert Bellah in order to argue that religion can and should be taught from what he terms a “neutral” standpoint that encourages critical inquiry. The role of the scholar of religion as a researcher, observer, and teacher is one that remains contended across the field of religious studies today.

Financial Reporting and Entrepreneurial Finance: Evidence from Equity Crowdfunding

2021 ◽  
Author(s):  
John Donovan
Keyword(s):  
Financial Reporting ◽  
Positive Association ◽  
Financial Statement ◽  
Entrepreneurial Finance ◽  
Ongoing Debate ◽  
Equity Crowdfunding ◽  
Macroeconomic Uncertainty ◽  
Ex Post ◽  
Insight Into

I study the role of accounting and financial reporting in entrepreneurial finance by examining whether financial statement disclosure increases capital raised through equity crowdfunding. On average, I find a positive association between financial reporting and capital raised, suggesting that accounting reduces information asymmetry with potential investors. Additionally, the importance of financial reporting in equity crowdfunding varies predictably in the cross-section. Specifically, financial reporting is associated with greater capital raised when the firm has longer historical operations, during periods of higher macroeconomic uncertainty, and when complemented by detailed shareholder agreements. Finally, using a mediation analysis, I find evidence that financial reporting is indirectly associated with better ex post performance by increasing the likelihood of raising capital. These results provide insight into the role of financial reporting in entrepreneurial finance and inform the ongoing debate over regulation and disclosure in the equity crowdfunding market. This paper was accepted by Brian Bushee, accounting.

Dialogic and Direct Instruction: Two Distinct Models of Mathematics Instruction and the Debate(s) Surrounding Them

2015 ◽  
Vol 117 (11) ◽  
pp. 1-32
Author(s):  
Charles Munter ◽  
Mary Kay Stein ◽  
Margaret S. Smith
Keyword(s):  
State Standards ◽  
Student Thinking ◽  
Instructional Models ◽  
Common Goal ◽  
Ongoing Debate ◽  
The Common ◽  
Points Of View ◽  
K 12 ◽  
Background Context

Background/Context Which ideas should be included in the K–12 curriculum, how they are learned, and how they should be taught have been debated for decades in multiple subjects. In this article, we offer mathematics as a case in point of how new standards-related policies may offer an opportunity for reassessment and clarification of such debates. Purpose/Objective Our goal was to specify instructional models associated with terms such as “reform” and “traditional”—which, in this article, we refer to as “dialogic” and “direct”—in terms of perspectives on what it means to know mathematics, how students learn mathematics, and how mathematics should be taught. Research Design In the spirit of “adversarial collaboration,” we hosted a series of semi-structured discussions among nationally recognized experts who hold opposing points of view on mathematics teaching and/or learning. During those discussions, the recent consensus regarding what students should learn—as represented by the Common Core State Standards for Mathematics (CCSSM)—was taken as a common goal, and additional areas of agreement and disagreement were identified and discussed. The goal was not to reach consensus but to invite representatives of different perspectives to clarify and come to agreement on how they disagree. Findings/Results We present two instructional models that were specified and refined over the course of those discussions and describe nine key areas that distinguish the two models: (a) the importance and role of talk; (b) the importance and role of group work; (c) the sequencing of mathematical topics; (d) the nature and ordering of mathematical instructional tasks; (e) the nature, timing, source, and purpose of feedback; (f) the emphasis on creativity (i.e., authoring one's own learning; mathematizing subject matter from reality); (g) the purpose of diagnosing student thinking; (h) the introduction and role of definitions; and (i) the nature and role of representations. Additionally, we elaborate a more nuanced description of the ongoing debate, as it pertains to particular sources of difference in perspective. Conclusions/Recommendations With this article, we hope to advance ongoing debates in two ways: (a) discrediting false assumptions and oversimplified conceptions of the “other side's” arguments (which can obscure both the real differences and real similarities between different models of instruction), and (b) framing the debates in a manner that allows for more thoughtful empirical investigation oriented to understanding learning in the discipline.

On the role of person in the mapping of syntactic features onto their interpretable counterparts

2019 ◽  
Vol 64 (4) ◽  
pp. 649-672
Author(s):  
Ivona Kučerová
Keyword(s):  
Division Of Labour ◽  
Special Focus ◽  
Semantic Features ◽  
Ongoing Debate ◽  
Syntactic Features ◽  
Person Features ◽  
The Subject

AbstractPerson features play a role in narrow-syntax processes. However, a person feature is often characterized as [±participant], a characterization that suggests pragmatic or semantic features. Relatedly, person has been the subject of an ongoing debate in the literature: one family of approaches argues that 3rd person is an elsewhere case, while another argues that it is a valued interpretable feature. This article provides a programatic argument that this disagreement has a principled basis. I argue that the representation of the features we identify as person changes between narrow syntax and the syntax-semantics interface. The tests and empirical descriptions are incongruent because they target different modules of the grammar and in turn different grammatical objects. The article thus contributes to our understanding of the division of labour among the modules, with a special focus on the autonomous status of narrow syntax.

“It's the Politics, Stupid.” Or is Reality more Complex?

2013 ◽  
Vol 4 (2) ◽  
pp. 297-306 ◽  
Author(s):  
Maria Weimer
Keyword(s):  
United States ◽  
Precautionary Principle ◽  
Significant Contribution ◽  
The United States ◽  
The Other ◽  
Ongoing Debate ◽  
Risk Regulation ◽  
The Precautionary Principle ◽  
The One

Reality is complex, and often does not lend itself to generalization or simplifying explanations. Yet at the same time, explaining reality often requires the shaping of notions and concepts of it through generalization and the reduction of complexity. This tension between complexity and particularity on the one hand and generalization and the search for abstracting explanatory patterns on the other is beautifully illustrated by two recently released publications on precaution and risk regulation in the United States and Europe, namely “The Politics of Precaution” by David Vogel1 and “The Reality of Precaution” edited by Jonathan Wiener, Michael Rogers, James Hammitt, and Peter Sand.Both books together can be seen as the latest significant contribution to the ongoing debate on the role of the precautionary principle in risk regulation in a comparative EU-US perspective. Both contributions are significant in that they consolidate the trend towards an empirically informed analysis of the actual practice of the application of precaution in risk regulation.

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