Natural selection in a population of Drosophila melanogaster explained by changes in gene expression caused by sequence variation in core promoter regions

Estimated regions of linkage disequilibrium and associations between SNPs and expression level in regions flanking CPRs for which sequence variation could explain gene expression variation and was subject to purifying selection or selective sweep. Flanking regions (±5000 bp) of CPRs for CG15743 (A), CG9044 (B), brat (C), Cyp4d1 (D), CG14253 (E), Nmda1 (F), CG6950 (G), CG10463 (H), and CG33506 (I) are shown. Gray shades indicate haplotype blocks within which linkage disequilibrium could be found. Orange bars indicate coding region. Green bar indicates CPR. Each dot indicates a false discovery rate value (FDR) using the Wald test for the association between expression levels and SNPs. Horizontal line indicates FDR threshold (α = 0.01). (PDF 626 kb

Evolution for the Next Generation

Do you want to know about evolution? Brian and Deborah Charlesworth provide an excellent and concise account of the core issues for a broad range of reader

A genetically explicit model of speciation by sensory drive within a continuous population in aquatic environments

<p>Abstract</p> <p>Background</p> <p>The sensory drive hypothesis predicts that divergent sensory adaptation in different habitats may lead to premating isolation upon secondary contact of populations. Speciation by sensory drive has traditionally been treated as a special case of speciation as a byproduct of adaptation to divergent environments in geographically isolated populations. However, if habitats are heterogeneous, local adaptation in the sensory systems may cause the emergence of reproductively isolated species from a single unstructured population. In polychromatic fishes, visual sensitivity might become adapted to local ambient light regimes and the sensitivity might influence female preferences for male nuptial color. In this paper, we investigate the possibility of speciation by sensory drive as a byproduct of divergent visual adaptation within a single initially unstructured population. We use models based on explicit genetic mechanisms for color vision and nuptial coloration.</p> <p>Results</p> <p>We show that in simulations in which the adaptive evolution of visual pigments and color perception are explicitly modeled, sensory drive can promote speciation along a short selection gradient within a continuous habitat and population. We assumed that color perception evolves to adapt to the modal light environment that individuals experience and that females prefer to mate with males whose nuptial color they are most sensitive to. In our simulations color perception depends on the absorption spectra of an individual's visual pigments. Speciation occurred most frequently when the steepness of the environmental light gradient was intermediate and dispersal distance of offspring was relatively small. In addition, our results predict that mutations that cause large shifts in the wavelength of peak absorption promote speciation, whereas we did not observe speciation when peak absorption evolved by stepwise mutations with small effect.</p> <p>Conclusion</p> <p>The results suggest that speciation can occur where environmental gradients create divergent selection on sensory modalities that are used in mate choice. Evidence for such gradients exists from several animal groups, and from freshwater and marine fishes in particular. The probability of speciation in a continuous population under such conditions may then critically depend on the genetic architecture of perceptual adaptation and female mate choice.</p

MOTOR UNIT FIRINGS DURING VOLUNTARY ISOMETRIC RAMP AND BALLISTIC CONTRACTIONS IN HUMAN VASTUS MEDIALIS MUSCLE

Intra-muscular electromyographic (EMG) signals in vastus medialis muscle were decomposed into their constituent motor unit action potential trains using a specially designed quadrifilar wire electrode during voluntary isometric ramp and ballistic contractions. Five male adults participated in our experiments as subjects and performed ramp trapezoidal, ramp triangular, and ballistic contractions. By using a newly developed wire electrode, intra-muscular EMG signals were successfully decomposed into the individual motor unit action potential trains. The firing behaviors analyzed by the decomposition technique were consistent with previous studies on small muscles. This new quadrifilar wire electrode is potentially a useful tool for detecting intra-muscular electromyographic signals in large limb muscles such as the vastus medialis

Size-dependent foraging gene expression and behavioral caste differentiation in Bombus ignitus

<p>Abstract</p> <p>Background</p> <p>In eusocial hymenopteran insects, <it>foraging </it>genes, members of the cGMP-dependent protein kinase family, are considered to contribute to division of labor through behavioral caste differentiation. However, the relationship between <it>foraging </it>gene expression and behavioral caste in honeybees is opposite to that observed in ants and wasps. In the previously examined eusocial Hymenoptera, workers behave as foragers or nurses depending on age. We reasoned that examination of a different system of behavioral caste determination might provide new insights into the relationship between <it>foraging </it>genes and division of labor, and accordingly focused on bumblebees, which exhibit size-dependent behavioral caste differentiation. We characterized a <it>foraging </it>gene (<it>Bifor</it>) in bumblebees (<it>Bombus ignitus</it>) and examined the relationship between <it>Bifor </it>expression and size-dependent behavioral caste differentiation.</p> <p>Findings</p> <p>A putative open reading frame of the <it>Bifor </it>gene was 2004 bp in length. It encoded 668 aa residues and showed high identity to orthologous genes in other hymenopterans (85.3-99.0%). As in ants and wasps, <it>Bifor </it>expression levels were higher in nurses than in foragers. <it>Bifor </it>expression was negatively correlated with individual body size even within the same behavioral castes (regression coefficient = -0.376, P < 0.001, all individuals; -0.379, <it>P </it>= 0.018, within foragers).</p> <p>Conclusion</p> <p>These findings indicate that <it>Bifor </it>expression is size dependent and support the idea that <it>Bifor </it>expression levels are related to behavioral caste differentiation in <it>B. ignitus</it>. Thus, the relationship between <it>foraging </it>gene expression and behavioral caste differentiation found in ants and wasps was identified in a different system of labor determination.</p

Evidence of introgressive hybridization between the morphologically divergent land snails Ainohelix and Ezohelix

Hybridization between different taxa is likely to take place when adaptive morphological differences evolve more rapidly than reproductive isolation. When studying the phylogenetic relationship between two land snails of different nominal genera, Ainohelix editha and Ezohelix gainesi, from Hokkaido, Japan, using nuclear internal transcribed spacer and mitochondrial 16S ribosomal DNA, we found a marked incongruence in the topology between nuclear and mitochondrial phylogenies. Furthermore, no clear association was found between shell morphology (which defines the taxonomy) and nuclear or mitochondrial trees and morphology of reproductive system. These patterns are most likely explained by historical introgressive hybridization between A. editha and E. gainesi. Because the shell morphologies of the two species are quite distinct, even when they coexist, the implication is that natural selection is able to maintain (or has recreated) distinct morphologies in the face of gene flow. Future studies may be able to reveal the regions of the genome that maintain the morphological differences between these species

Antimicrobial Ointments and Methicillin-Resistant Staphylococcus aureus USA300

We tested 259 methicillin-resistant Staphylococcus aureus isolates and 2 USA300 ATCC type strains for susceptibility to bacitracin and neomycin contained in over-the-counter antibacterial ointments. Resistance to both bacitracin and neomycin was found only in USA300. The use of over-the counter antimicrobial drugs may select for the USA300 clone