Selection Arena Research Articles

A new human embryonic cell type associated with activity of young transposable elements allows definition of the inner cell mass.

There remains much that we do not understand about the earliest stages of human development. On a gross level, there is evidence for apoptosis, but the nature of the affected cell types is unknown. Perhaps most importantly, the inner cell mass (ICM), from which the foetus is derived and hence of interest in reproductive health and regenerative medicine, has proven hard to define. Here, we provide a multi-method analysis of the early human embryo to resolve these issues. Single-cell analysis (on multiple independent datasets), supported by embryo visualisation, uncovers a common previously uncharacterised class of cells lacking commitment markers that segregates after embryonic gene activation (EGA) and shortly after undergo apoptosis. The discovery of this cell type allows us to clearly define their viable ontogenetic sisters, these being the cells of the ICM. While ICM is characterised by the activity of an Old non-transposing endogenous retrovirus (HERVH) that acts to suppress Young transposable elements, the new cell type, by contrast, expresses transpositionally competent Young elements and DNA-damage response genes. As the Young elements are RetroElements and the cells are excluded from the developmental process, we dub these REject cells. With these and ICM being characterised by differential mobile element activities, the human embryo may be a "selection arena" in which one group of cells selectively die, while other less damaged cells persist.

The human embryo selection arena is associated with transposable element activity.

Our current understanding of early human development is limited. A study in PLOS Biology found a previously undefined group of cells that diverges from the main lineages and undergo apoptosis through the activity of young transposable elements.

Seminal Fluid-Mediated Manipulation of Post-mating Behavior in a Simultaneous Hermaphrodite

Seminal fluid proteins (SFPs) are uniquely positioned to mediate post-mating sexual selection and sexual conflict [1-3]. This role may be especially important in simultaneous hermaphrodites, in which individuals will often agree to receive sperm in order to be able to donate it, shifting the arena of sexual selection to post-mating reproductive interactions [4-7]. Nevertheless, as in separate-sexed organisms, identifying individual SFPs responsible for specific post-mating effects is difficult, owing to the complexity, rapid evolution, and functional redundancy of seminal fluid [8-11]. Here, we sought to identify SFPs that influence one striking post-mating behavior of the simultaneously hermaphroditic flatworm Macrostomum lignano, the so-called "suck behavior," in which worms respond to ejaculate receipt by placing their pharynx over their female genital opening and seemingly attempt to remove sperm and/or other ejaculate components [12-14]. We hypothesized that sucking is counter to the sperm donor's interests, potentially selecting for SFPs that reduce the suck propensity of mating partners. We tested this using a combination of quantitative genetics and RNA interference (RNAi) knockdown. As predicted, we found negative genetic correlations between the expression levels of six (outof 58) seminal fluid transcripts and partner suck propensity. RNAi knockdown confirmed that two of these transcripts, designated suckless-1 and suckless-2, indeed caused mating partners to suck less often. We suggest that these proteins are male counter-adaptations to recipient suck behavior, which itself is likely a female counter-adaptation in the ongoing evolutionary conflict to (re)gain control over ejaculate fate after mating in this hermaphroditic organism.

Applicant Perspectives During Selection: A Review Addressing “So What?,” “What’s New?,” and “Where to Next?”

We provide a comprehensive but critical review of research on applicant reactions to selection procedures published since 2000 ( n = 145), when the last major review article on applicant reactions appeared in the Journal of Management. We start by addressing the main criticisms levied against the field to determine whether applicant reactions matter to individuals and employers (“So what?”). This is followed by a consideration of “What’s new?” by conducting a comprehensive and detailed review of applicant reaction research centered upon four areas of growth: expansion of the theoretical lens, incorporation of new technology in the selection arena, internationalization of applicant reactions research, and emerging boundary conditions. Our final section focuses on “Where to next?” and offers an updated and integrated conceptual model of applicant reactions, four key challenges, and eight specific future research questions. Our conclusion is that the field demonstrates stronger research designs, with studies incorporating greater control, broader constructs, and multiple time points. There is also solid evidence that applicant reactions have significant and meaningful effects on attitudes, intentions, and behaviors. At the same time, we identify some remaining gaps in the literature and a number of critical questions that remain to be explored, particularly in light of technological and societal changes.

Capitalism: restless and unbounded? Some neo-Polanyian and Schumpeterian reflections

This paper first explores the notion that the limitlessness of knowledge is a privileged source of the restlessness of capitalism [Metcalfe, J. S. 2001. “Institutions and Progress.” Industrial and Corporate Change 10 (3): 561–586; 2002. “Knowledge of Growth and Growth of Knowledge.” Journal of Evolutionary Economics 12 (1): 3–13; 2004. “The Entrepreneur and the Style of Modern Economies.” Journal of Evolutionary Economics 14 (2): 157–175; 2010. “University and Business Relations: Connecting the Knowledge Economy.” Minerva 48 (1): 5–33] when combined with incentives of entrepreneurialism in a market society. Metcalfe gives a central paradigm of evolutionary economics a distinctive turn, with knowledge the pre-eminent source of variation, and markets the primary arena of selection. The paper engages this approach with a neo-Polanyian approach of ‘instituted economic process’, in which the variation and selection dynamic is itself seen as instituted within a particular historical economic context. The paper develops a critique of the evolutionary paradigm firstly by suggesting variations in instituted ‘economies of knowledge’ within a multi-modal conception of capitalism. Further breaking with the bipolar variation-selection paradigm, the paper argues that there has been a significant role of the state as a distinctive source of variation and selection in innovation and economic transformation. This leads us finally to analyse the shifting place of economy in society and polity, and the strategic responses in the USA, Brazil and Europe to the historically novel conjuncture of peak oil and global climate change, as a further source of variation. We conclude that a choice between evolutionary and historical approaches to innovation and economic transformation is a false one, once a universalising and unbounded paradigm of variation and selection is abandoned.

Deleterious effects of recombination and possible nonrecombinatorial advantages of sex in a fungal model

Why sexual reproduction is so prevalent in nature remains a major question in evolutionary biology. Most of the proposed advantages of sex rely on the benefits obtained from recombination. However, it is still unclear whether the conditions under which these recombinatorial benefits would be sufficient to maintain sex in the short term are met in nature. Our study addresses a largely overlooked hypothesis, proposing that sex could be maintained in the short term by advantages due to functions linked with sex, but not related to recombination. These advantages would be so essential that sex could not be lost in the short term. Here, we used the fungus Aspergillus nidulans to experimentally test predictions of this hypothesis. Specifically, we were interested in (i) the short-term deleterious effects of recombination, (ii) possible nonrecombinatorial advantages of sex particularly through the elimination of mutations and (iii) the outcrossing rate under choice conditions in a haploid fungus able to reproduce by both outcrossing and haploid selfing. Our results were consistent with our hypotheses: we found that (i) recombination can be strongly deleterious in the short term, (ii) sexual reproduction between individuals derived from the same clonal lineage provided nonrecombinatorial advantages, likely through a selection arena mechanism, and (iii) under choice conditions, outcrossing occurs in a homothallic species, although at low rates.

The shifting landscape of e‐books

PurposeThe purpose of this paper is to review the current state of e‐books, describing their potential scope, highlighting information from recent ebrary surveys in connection with the author's on‐the‐ground experience with students, and discussing the challenges of these evolving works.Design/methodology/approachThe paper describes the need to broaden perceptions of e‐books in light of their extensive potential and scope. It highlights significant points in the ebrary surveys and compares them with the author's on‐the‐ground experience in a medium‐sized university with students who are less advantaged. It also presents the challenges librarians face, both currently and in the future, illustrating progress in some areas and emphasizing the growing complexity in managing these works.FindingsEven as librarians cope with what can now be considered “traditional” e‐books, little attention is paid to the potential breadth and diversity of e‐books. The surveys show that librarians are only partially aware of students' perceptions about e‐books and that there are conflicting priorities among students, faculty, and librarians. Conclusions are that: even as librarians cope with the current state of e‐books, they must also plan for future types of e‐books; and there is a strong need for greater communication in the increasingly complex e‐book arena of selection, acquisition, collection integration, and instruction.Originality/valueMuch of the literature about e‐books deals with the pros and cons, either of e‐books or of e‐book readers. The paper lays out e‐book issues to foster further in‐depth discussion.

Issues in evolutionary medicine

This paper illustrates the utility of applying evolutionary thought to medical issues with three examples: selection arenas, aging, and tradeoffs. First, the human female reproductive tract functions as a selection arena at two levels: in the ovaries, where atresia reduces the number of oocytes by more than 99.99% before any are ovulated, and in the uterus, where early embryos homozygous for immune genes are spontaneously aborted. These selective filters early in life have implications both for eugenics and for the anti-abortion movement. Second, the evolutionary theory of aging predicts that intrinsic mortality should reflect extrinsic mortality: if life for adults is risky, then it does not pay to invest in maintenance at the expense of reproduction. This idea is well confirmed, at least in populations where density effects are not important. While only organisms that reproduce asymmetrically should age, even bacteria reproduce asymmetrically, and they do age, suggesting that all organisms reproduce asymmetrically and therefore age. Third, tradeoffs are central to theories of phenotypic design, but the mechanisms that cause them remain obscure. A method is suggested to get at the mechanisms of tradeoffs by examining conflicts among functions over gene expression. It could be applied in humans to the tradeoff between reproductive performance and disease resistance.

Selection arena in Aspergillus nidulans

The selection arena hypothesis states that overproduction of zygotes—a widespread phenomenon in animals and plants—can be explained as a mechanism of progeny choice. As a similar mechanism, the ascomycetous fungus Aspergillus nidulans may overproduce dikaryotic fruit initials, hereafter called dikaryons. Then, progeny choice might involve selection on which of these dikaryons will thrive to produce thousands of zygotes. These zygotes each produce eight sexual spores which together fill up one fruiting body. In this study, we test the selection arena hypothesis in this homothallic fungus that produces both sexual and asexual spores. We analyzed two mitochondrial and 15 auxotrophic mutations for consequences on sexual and asexual reproduction. We found that many of these mutations confer sexual self-sterility as a pleiotropic effect under conditions of normal asexual spore production. This confirms an important prediction of the selection arena, namely that dikaryons carrying a (slightly) deleterious mutation are not able to proliferate and produce sexual spores. The selection arena ensures that reproductive energy is invested mainly in dikaryons and thus sexual spores of good genetic quality.

Perspective: female remating, operational sex ratio, and the arena of sexual selection in Drosophila species.

As commonly observed among closely related species within a variety of taxa, Drosophila species differ considerably in whether they exhibit sexual dimorphism in coloration or morphology. Those Drosophila species in which male external sexual characters are minimal or absent tend, instead, to have exaggerated ejaculate traits such as sperm gigantism or seminal nutrient donations. Underlying explanations for the interspecific differences in the presence of external morphological sexual dimorphism versus exaggerated ejaculate traits are addressed here by examining the opportunity for sexual selection on males to occur before versus after mating in 21 species of Drosophila. Female remating frequency, an important component of the operational sex ratio, differs widely among Drosophila species and appears to dictate whether the arena of sexual selection is prior to, as opposed to after, copulation. Infrequent female mating results in fewer mating opportunities for males and thus stronger competition for receptive females that favors the evolution of male characters that maximize mating success. On the other hand, rapid female remating results in overlapping ejaculates in the female reproductive tract, such that ejaculate traits which enhance fertilization success are favored. The strong association between female remating frequency in a given species and the presence of sexually selected external versus internal male characters indicates that the relationship be examined in other taxa as well.

PERSPECTIVE: FEMALE REMATING, OPERATIONAL SEX RATIO, AND THE ARENA OF SEXUAL SELECTION IN DROSOPHILA SPECIES

As commonly observed among closely related species within a variety of taxa, Drosophila species differ considerably in whether they exhibit sexual dimorphism in coloration or morphology. Those Drosophila species in which male external sexual characters are minimal or absent tend, instead, to have exaggerated ejaculate traits such as sperm gigantism or seminal nutrient donations. Underlying explanations for the interspecific differences in the presence of external morphological sexual dimorphism versus exaggerated ejaculate traits are addressed here by examining the opportunity for sexual selection on males to occur before versus after mating in 21 species of Drosophila. Female remating frequency, an important component of the operational sex ratio, differs widely among Drosophila species and appears to dictate whether the arena of sexual selection is prior to, as opposed to after, copulation. Infrequent female mating results in fewer mating opportunities for males and thus stronger competition for receptive females that favors the evolution of male characters that maximize mating success. On the other hand, rapid female remating results in overlapping ejaculates in the female reproductive tract, such that ejaculate traits which enhance fertilization success are favored. The strong association between female remating frequency in a given species and the presence of sexually selected external versus internal male characters indicates that the relationship be examined in other taxa as well.