76 research outputs found
Effects of Ploidy and Recombination on Evolution of Robustness in a Model of the Segment Polarity Network
Many genetic networks are astonishingly robust to quantitative variation,
allowing these networks to continue functioning in the face of mutation and
environmental perturbation. However, the evolution of such robustness remains
poorly understood for real genetic networks. Here we explore whether and how
ploidy and recombination affect the evolution of robustness in a detailed
computational model of the segment polarity network. We introduce a novel
computational method that predicts the quantitative values of biochemical
parameters from bit sequences representing genotype, allowing our model to
bridge genotype to phenotype. Using this, we simulate 2,000 generations of
evolution in a population of individuals under stabilizing and truncation
selection, selecting for individuals that could sharpen the initial pattern of
engrailed and wingless expression. Robustness was measured by simulating a
mutation in the network and measuring the effect on the engrailed and wingless
patterns; higher robustness corresponded to insensitivity of this pattern to
perturbation. We compared robustness in diploid and haploid populations, with
either asexual or sexual reproduction. In all cases, robustness increased, and
the greatest increase was in diploid sexual populations; diploidy and sex
synergized to evolve greater robustness than either acting alone. Diploidy
conferred increased robustness by allowing most deleterious mutations to be
rescued by a working allele. Sex (recombination) conferred a robustness
advantage through “survival of the compatible”: those
alleles that can work with a wide variety of genetically diverse partners
persist, and this selects for robust alleles
Evolution of Sex Chromosome Dosage Compensation in Animals: A Beautiful Theory, Undermined by Facts and Bedeviled by Details
Many animals with genetic sex determination harbor heteromorphic sex chromosomes, where the heterogametic sex has half the gene dose of the homogametic sex. This imbalance, if reflected in the abundance of transcripts or proteins, has the potential to deleteriously disrupt interactions between X-linked and autosomal loci in the heterogametic sex. Classical theory predicts that molecular mechanisms will evolve to provide dosage compensation that recovers expression levels comparable to ancestral expression prior to sex chromosome divergence. Such dosage compensating mechanisms may also, secondarily, result in balanced sex-linked gene expression between males and females. However, numerous recent studies addressing sex chromosome dosage compensation (SCDC) in a diversity of animals have yielded a surprising array of patterns concerning dosage compensation in the heterogametic sex, as well as dosage balance between sexes. These results substantially contradict longstanding theory, catalyzing both novel perspectives and new approaches in dosage compensation research. In this review, we summarize the theory, analytical approaches, and recent results concerning evolutionary patterns of SCDC in animals. We also discuss methodological challenges and discrepancies encountered in this research, which often underlie conflicting results. Finally, we discuss what outstanding questions and opportunities exist for future research on SCDC
COI barcode versus morphological identification of Culex ( Culex ) (Diptera: Culicidae) species: a case study using samples from Argentina and Brazil
Post-glacial hunter-gatherer subsistence patterns in Britain:Dietary reconstruction using FRUITS
Heterogeneous natural selection on oxidative phosphorylation genes among fishes with extreme high and low aerobic performance
Background: Oxidative phosphorylation (OXPHOS) is the primary source of ATP in eukaryotes and serves as a mechanistic link between variation in genotypes and energetic phenotypes. While several physiological and anatomical factors may lead to increased aerobic capacity, variation in OXPHOS proteins may influence OXPHOS efficiency and facilitate adaptation in organisms with varied energy demands. Although there is evidence that natural selection acts on OXPHOS genes, the focus has been on detection of directional (positive) selection on specific phylogenetic branches where traits that increase energetic demands appear to have evolved. We examined patterns of selection in a broader evolutionary context, i.e., on multiple lineages of fishes with extreme high and low aerobic performance.
Results: We found that patterns of natural selection on mitochondrial OXPHOS genes are complex among fishes with different swimming performance. Positive selection is not consistently associated with high performance taxa and appears to be strongest on lineages containing low performance taxa. In contrast, within high performance lineages, purifying (negative) selection appears to predominate.
Conclusions: We provide evidence that selection on OXPHOS varies in both form and intensity within and among lineages through evolutionary time. These results provide evidence for fluctuating selection on OXPHOS associated with divergence in aerobic performance. However, in contrast to previous studies, positive selection was strongest on low performance taxa suggesting that adaptation of OXPHOS involves many factors beyond enhancing ATP production in high performance taxa. The broader pattern indicates a complex interplay between organismal adaptations, ATP demand, and OXPHOS function.This work was supported by NSF award DEB-0732988 (to REB).Ye
Mindfulness at Work: Positive Affect, Hope, and Optimism Mediate the Relationship Between Dispositional Mindfulness, Work Engagement, and Well-Being
Mindfulness has been described as a state of awareness characterized by refined attentional skills and a non-evaluative attitude toward internal and external events. Recently it has been suggested that higher levels of mindfulness may be beneficial in the workplace and first programs aiming to increase mindful awareness in occupational settings have been introduced. The current study underpins these developments with empirical evidence regarding the involved psychological processes, by investigating the relationship between dispositional mindfulness, work engagement and well-being in 299 adults in fulltime employment. As hypothesized, the results confirm that self-reported mindfulness predicts work engagement and general well-being. Furthermore, these relationships are mediated by positive job-related affect and psychological capital (hope, optimism, resiliency, and self-efficacy). Investigating mindfulness and psychological capital as multi-faceted concepts by means of structural equation modeling yielded a more precise picture. The ability to step back from automatic, habitual reactions to distress turned out to be the mindfulness facet most central for predicting work engagement and well-being. Furthermore, mindfulness exerts its positive effect on work engagement by increasing positive affect, hope, and optimism, which on their own and in combination enhance work engagement (full mediation). Well-being, on the other hand, is directly influenced by mindfulness, which exerts additional indirect influence via positive affect, hope and optimism (partial mediation). Although exploratory in nature, the results identify non-reactivity and non-judging as important mindfulness skills in the workplace
Development of a text message intervention aimed at reducing alcohol-related harm in patients admitted to hospital as a result of injury
Selfish drive can trump function when animal mitochondrial genomes compete.
Mitochondrial genomes compete for transmission from mother to progeny. We explored this competition by introducing a second genome into Drosophila melanogaster to follow transmission. Competitions between closely related genomes favored those functional in electron transport, resulting in a host-beneficial purifying selection. In contrast, matchups between distantly related genomes often favored those with negligible, negative or lethal consequences, indicating selfish selection. Exhibiting powerful selfish selection, a genome carrying a detrimental mutation displaced a complementing genome, leading to population death after several generations. In a different pairing, opposing selfish and purifying selection counterbalanced to give stable transmission of two genomes. Sequencing of recombinant mitochondrial genomes showed that the noncoding region, containing origins of replication, governs selfish transmission. Uniparental inheritance prevents encounters between distantly related genomes. Nonetheless, in each maternal lineage, constant competition among sibling genomes selects for super-replicators. We suggest that this relentless competition drives positive selection, promoting change in the sequences influencing transmission
Sarcophaga maxima sp. nov. (Diptera: Sarcophagidae: Sarcophaginae), a new Australian flesh fly recognised by morphology and DNA barcoding
A new species, Sarcophaga (Sarcorohdendorfia) maxima sp. nov., supported by both morphological and DNA barcoding data, is described from Queensland and New South Wales, Australia. The major morphological features of the new species are listed, and the male terminalia are documented with both photography and scanning electron microscopy. Sarcophaga alcicornis Hardy, 1932 is transferred from subgenus Lioproctia Enderlein to Sarcorohdendorfia Baranov
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