Variation of selfing rate and inbreeding depression among individuals and across generations within an admixed Cedrus population

[EN] We investigated the variation and short-term evolution of the selfing rate and inbreeding depression (ID) across three generations within a cedar forest that was established from admixture ca 1860. The mean selfing rate was 9.5%, ranging from 0 to 48% among 20 seed trees (estimated from paternally inherited chloroplast DNA). We computed the probability of selfing for each seed and we investigated ID by comparing selfed and outcrossed seeds within progenies, thus avoiding maternal effects. In all progenies, the germination rate was high (88-100%) and seedling mortality was low (0-12%). The germination dynamics differed significantly between selfed and outcrossed seeds within progenies in the founder gene pool but not in the following generations. This transient effect of selfing could be attributed to epistatic interactions in the original admixture. Regarding the seedling growth traits, the ID was low but significant: 8 and 6% for height and diameter growth, respectively. These rates did not vary among generations, suggesting minor gene effects. At this early stage, outcrossed seedlings outcompeted their selfed relatives, but not necessarily other selfed seedlings from other progenies. Thus, purging these slightly deleterious genes may only occur through within-family selection. Processes that maintain a high level of genetic diversity for fitness-related traits among progenies also reduce the efficiency of purging this part of the genetic load. © 2011 Macmillan Publishers Limited All rights reserved. Guardar / Salir Siguiente >This work has been partially supported by Grant PPI-00-04 from the Polytechnic University of Valencia (Spain). We thank B Fady and E Klein as well as two anonymous reviewers for their helpful comments on a previous version of the paper. We acknowledge B Jouaud, W Brunetto, F Jean and H Picot for seed collection and processing and laboratory assistance, as well as P Brahic and staff from the Experimental Nursery of Aix-Les Milles for nursery cares.Ferriol Molina, M.; Pichot, C.; Lefevre, F. (2011). Variation of selfing rate and inbreeding depression among individuals and across generations within an admixed Cedrus population. Heredity. 106(1):146-157. https://doi.org/10.1038/hdy.2010.451461571061Barret SH, Eckert CG (1990). Variation and evolution of mating systems in seed plants. In: Kawano S (ed). Biological Approaches and Evolutionary Trends in Plants. Academic Press: London. pp 230–254.Benton TG, Plaistow SJ, Coulson TN (2006). Complex population dynamics and complex causation: devils, details and demography. Proc R Soc B Biol Sci 273: 1173–1181.Bower AD, Aitken SN (2007). Mating system and inbreeding depression in whitebark pine (Pinus albicaulis Engelm.). Tree Genet Genomes 3: 379–388.Byers DL, Waller DM (1999). Do plant populations purge their genetic load? Effects of population size and mating history on inbreeding depression. Annu Rev Ecol Syst 30: 479–513.Cointat M (1996). Le roman du cèdre. Revue Forestière Française 48: 503–526.Collevatti RG, Grattapaglia D, Duvall J (2001). High resolution microsatellite based analysis of the mating system allows the detection of significant biparental inbreeding in Caryocar brasiliense, an endangered tropical tree species. Heredity 86: 60–67.Cottrell JE, White IMS (1995). The use of isozyme genetic markers to estimate the rate of outcrossing in a Sitka pruce (Picea sitchensis (Bong.) Carr.) seed orchard in Scotland. New Forests 10: 111–122.Coulson T, Benton TG, Lundberg P, Dall SRX, Kendall BE (2006). Putting evolutionary biology back in the ecological theatre: a demographic framework mapping genes to communities. Evol Ecol Res 8: 1155–1171.Durel CE, Bertin P, Kremer A (1996). Relationship between inbreeding depression and inbreeding coefficient in maritime pine (Pinus pinaster). Theor Appl Genet 92: 347–356.Eriksson E (2006). Thinning operations and their impact on biomass production in stands of Norway spruce and Scots pine. Biomass Bioenergy 30: 848–854.Fady B, Lefèvre F, Reynaud M, Vendramin GG, Bou Dagher-Karrat M, Anzidei M et al. (2003). Gene flow among different taxonomic units: evidence from nuclear and cytoplasmic markers in Cedrus plantation forests. Theor Appl Genet 107: 1132–1138.Farris MA, Mitton JB (1984). Population density, outcrossing rate, and heterozygote superiority in ponderosa pine. Evolution 38: 1151–1154.Favre-Duchartre M (1970). Des Ovules Aux Graines. Monographie 8. Masson et Cie.: Paris.Franklin EC (1969). Inbreeding Depression in Metrical Traits of Loblolly Pine (Pinus taeda L.) as a Result of Self-pollination. North Carolina State University: Raleigh, NC. Technical report No 40, School of Forest Resources.Gregorius HR, Ziehe M, Ross MD (1987). Selection caused by self-fertilization I. Four measures of self-fertilization and their effects on fitness. Theor Popul Biol 31: 91–115.Hamrick JL, Godt MJ (1989). Allozyme diversity in plant species. In: Brown AHD, Al Kahler MC, Weir BS (eds). Plant Population Genetics, Breeding, and Genetic Resources. Sinauer: Sunderland, MA. pp 43–63.Holsinger KE (1991). Mass-action models of plant mating systems—the evolutionary stability of mixed mating systems. Am Nat 138: 606–622.Husband BC, Schemske DW (1996). Evolution of the magnitude and timing of inbreeding depression in plants. Evolution 50: 54–70.Jones FA, Hamrick JL, Peterson CJ, Squiers ER (2006). Inferring colonization history from analyses of spatial genetic structure within populations of Pinus strobus and Quercus rubra. Mol Ecol 15: 851–861.Kärkkäinen K, Savolainen O (1993). The degree of early inbreeding depression determines the selfing rate at the seed stage: model and results from Pinus sylvestris (Scots pine). Heredity 71: 160–166.Keller LF, Waller DM (2002). Inbreeding effects in wild populations. Trends Ecol Evol 17: 230–241.Klein EK, Lavigne C, Gouyon PH (2006). Mixing of propagules from discrete sources at long distance: comparing an exponential tail to an exponential. BMC Ecol 6: 3.Knowles P, Furnier GR, Aleksiuk MK, Perry DJ (1987). Significant levels of self-fertilization in natural populations of tamarack. Can J Bot 65: 1087–1091.Koelewijn HP, Koski V, Savolainen O (1999). Magnitude and timing of inbreeding depression in Scots pine (Pinus sylvestris L.). Evolution 53: 758–768.Kremer A (1994). Genetic diversity and phenotypic variability of forest trees. Genet Sel Evol 26: s105–s123.Krouchi F, Derridj A, Lefèvre F (2004). Year and tree effect on reproductive organisation of Cedrus atlantica in a natural forest. For Ecol Manage 197: 181–189.Lande R (1988). Genetics and demography in biological conservation. Science 241: 1455–1460.Ledig FT (1986). Heterozygosity, heterosis, and fitness in outbreeding plants. In: Soulé ME (ed). Conservation Biology: the Science of Scarcity and Diversity. Sinauer Ass: Sunderland. pp 77–104.Lee JK, Nordheim EV, Kang H (1996). Inference for lethal gene estimation with application in plants. Biometrics 52: 451–462.Lefèvre F, Fady B, Fallour-Rubio D, Ghosn D, Bariteau M (2004). Impact of founder population, drift and selection on the genetic diversity of a recently translocated tree population. Heredity 93: 542–550.Marquardt PE, Epperson BK (2004). Spatial and population genetic structure of microsatellites in white pine. Mol Ecol 13: 3305–3315.Morgante M, Vendramin GG, Rossi P (1991). Effects of stand density on outcrossing rate in two Norway spruce (Picea abies) populations. Can J Bot 69: 2704–2708.Mosseler A, Major JE, Simpson JD, Daigle B, Lange K, Park YS et al. (2000). Indicators of population viability in red spruce, Picea rubens. I. Reproductive traits and fecundity. Can J Bot 78: 928–940.Naydenov KD, Tremblay FM, Alexandrov A, Fenton NJ (2005). Structure of Pinus sylvestris L. populations in Bulgaria revealed by chloroplast microsatellites and terpenes analysis : provenance tests. Biochem Syst Ecol 33: 1226–1245.Neale DB, Adams WT (1985). The mating system in natural and shelterwood stands of Douglas-fir. Theor Appl Genet 71: 201–207.Notivol E, Garcia-Gil MR, Alia R, Savolainen O (2007). Genetic variation of growth rhythm traits in the limits of a latitudinal cline in Scots pine. Can J For Res 37: 540–551.O’Connell LM, Russell J, Ritland K (2004). Fine-scale estimation of outcrossing in western redcedar with microsatellite assay of bulked DNA. Heredity 93: 443–449.Parducci L, Szmidt AE, Madaghiele A, Anzidei M, Vendramin GG (2001). Genetic variation at chloroplast microsatellites (CpSSRs) in Abies nebrodensis (Lojac.) Mattei and three neighboring Abies species. Theor Appl Genet 102: 733–740.Parraguirre-Lezama C, Vargas-Hernández JJ, Ramirez-Vallejo P, Ramirez Herrera C (2004). Mating system in four natural populations of Pinus greggii Engelm. Agrociencia 38: 107–119.Petit RJ, Hampe A (2006). Some evolutionary consequences of being a tree. Annu Rev Ecol Evol Syst 37: 187–214.Pichot C, Bastien C, Courbet F, Demesure-Musch B, Dreyfus P, Fady B et al. (2006). Déterminants et conséquences de la qualité génétique des graines et semis lors de la phase initiale de régénération naturelle des peuplements forestiers. In: 6e Colloque National du BRG ; La Rochelle 2006/10/02-04. Les Actes du Bureau des Ressources Génétiques 6: 277–297.Remington DL, O’Malley DM (2000a). Whole-genome characterization of embryonic stage inbreeding depression in a selfed loblolly pine family. Genetics 155: 337–348.Remington DL, O’Malley DM (2000b). Evaluation of major genetic loci contributing to inbreeding depression for survival and early growth in a selfed family of Pinus taeda. Evolution 54: 1580–1589.Restoux G, Silva DE, Sagnard F, Torre F, Klein E, Fady B (2008). Life at the margin: the mating system of Mediterranean conifers. Web Ecol 8: 94–102.Ribeiro MM, Mariette S, Vendramin GG, Szmidt AE, Plomion C, Kremer A (2002). Comparison of genetic diversity estimates within and among populations of maritime pine using chloroplast simple-sequence repeat and amplified fragment length polymorphism data. Mol Ecol 11: 869–877.Ritland K, El-Kassaby YA (1985). The nature of inbreeding in a seed orchard of Douglas fir as shown by an efficient multi-locus model. Theor Appl Genet 71: 375–384.Ritland K, Travis S (2004). Inferences involving individual coefficients of relatedness and inbreeding in natural populations of Abies. For Ecol Manage 197: 171–180.Robledo-Arnuncio JJ, Alia R, Gil L (2004). Increased selfing and correlated paternity in a small population of a predominantly outcrossing conifer, Pinus sylvestris. Mol Ecol 13: 2567–2577.Rouault G, Turgeon J, Candau JN, Roques A, Aderkas P (2004). Oviposition strategies of conifer seed chalcids in relation to host phenology. Naturwissenschaften 91: 472–480.Savolainen O, Kärkkäinen K, Kuittinen H (1992). Estimating numbers of embryonic lethals in conifers. Heredity 69: 308–314.Scofield DG, Schultz ST (2006). Mitosis, stature and evolution of plant mating systems: low-Phi and high-Phi plants. Proc R Soc B Biol Sci 273: 275–282.Shaw DV, Allard RW (1982). Estimation of outcrossing rates in douglas-fir using isoenzyme markers. Theor Appl Genet 62: 113–120.Skrøppa T (1996). Diallel crosses in Picea abies. II. Performance and inbreeding depression of selfed families. For Genet 3: 69–79.Sorensen FC (1997). Effects of sib mating and wind pollination on nursery seedling size, growth components, and phenology of Douglas-fir seed-orchard progenies. Can J For Res 27: 557–566.Sorensen FC (1999). Relationship between self-fertility, allocation of growth, and inbreeding depression in three coniferous species. Evolution 53: 417–425.Sorensen FC (2001). Effect of population outcrossing rate on inbreeding depression in Pinus contorta var. murrayana seedlings. Scand J For Res 16: 391–403.Sorensen FC, Adams WT (1993). Self fertility and natural selfing in three Oregon Cascade populations of lodgepole pine. In: Lindgren D (ed). Pinus contorta—From Untamed Forest to Domesticated Crop. Department of Forest Genetics and Plant Physiology, Sweden University of Agricultural Science: Umea, Sweden. Report 11, pp 358–374.Sorensen FC, Miles RS (1974). Self-pollination effects on Douglas fir and ponderosa pine seeds and seedlings. Silvae Genet 23: 135–138.Sorensen FC, Miles RS (1982). Inbreeding depression in height, height growth, and survival of Douglas-fir, ponderosa pine, and noble fir to 10 years of age. For Sci 28: 283–292.Terrab A, Paun O, Talavera S, Tremetsberger K, Arista M, Stuessy TF (2006). Genetic diversity and population structure in natural populations of Moroccan Atlas cedar (Cedrus atlantica; Pinaceae) determined with cpSSR markers. Am J Bot 93: 1274–1280.Vendramin GG, Lelli L, Rossi P, Morgante M (1996). A set of primers for the amplification of 20 chloroplast microsatellites in Pinaceae. Mol Ecol 5: 595–598.White TL, Adams WT, Neale DB (2007). Forest Genetics. CABI Publisher: Cambridge, MA. pp 149–186.Wilcox MD (1983). Inbreeding depression and genetic variances estimated from self- and cross- pollinated families of Pinus radiata. Silvae Genet 32: 89–96.Williams CG (2007). Re-thinking the embryo lethal system within the Pinaceae. Can J Bot 85: 667–677.Williams CG (2008). Selfed embryo death in Pinus taeda: a phenotypic profile. New Phytol 178: 210–222.Williams CG, Auckland LD, Reynolds MM, Leach KA (2003). Overdominant lethals as part of the conifer embryo lethal system. Heredity 91: 584–592.Wilson R (1923). Life history of Cedrus atlantica. Bot Gaz 75: 203–208.Yazdani R, Muona O, Rudin D, Szmidt AE (1985). Genetic structure of a Pinus sylvestris L. seed-tree stand and naturally regenerated understory. For Sci 31: 430–436

Evolutionary connectionism: algorithmic principles underlying the evolution of biological organisation in evo-devo, evo-eco and evolutionary transitions

The mechanisms of variation, selection and inheritance, on which evolution by natural selection depends, are not fixed over evolutionary time. Current evolutionary biology is increasingly focussed on understanding how the evolution of developmental organisations modifies the distribution of phenotypic variation, the evolution of ecological relationships modifies the selective environment, and the evolution of reproductive relationships modifies the heritability of the evolutionary unit. The major transitions in evolution, in particular, involve radical changes in developmental, ecological and reproductive organisations that instantiate variation, selection and inheritance at a higher level of biological organisation. However, current evolutionary theory is poorly equipped to describe how these organisations change over evolutionary time and especially how that results in adaptive complexes at successive scales of organisation (the key problem is that evolution is self-referential, i.e. the products of evolution change the parameters of the evolutionary process). Here we first reinterpret the central open questions in these domains from a perspective that emphasises the common underlying themes. We then synthesise the findings from a developing body of work that is building a new theoretical approach to these questions by converting well-understood theory and results from models of cognitive learning. Specifically, connectionist models of memory and learning demonstrate how simple incremental mechanisms, adjusting the relationships between individually-simple components, can produce organisations that exhibit complex system-level behaviours and improve the adaptive capabilities of the system. We use the term “evolutionary connectionism” to recognise that, by functionally equivalent processes, natural selection acting on the relationships within and between evolutionary entities can result in organisations that produce complex system-level behaviours in evolutionary systems and modify the adaptive capabilities of natural selection over time. We review the evidence supporting the functional equivalences between the domains of learning and of evolution, and discuss the potential for this to resolve conceptual problems in our understanding of the evolution of developmental, ecological and reproductive organisations and, in particular, the major evolutionary transitions

Research agenda for preventing mosquito-transmitted diseases through improving the built environment in sub-Saharan Africa

Mosquito-transmitted diseases are a major threat to health in sub-Saharan Africa, but could be reduced through modifications to the built environment. Here we report findings from a major workshop held to identify the research gaps in this area, namely: (1) evidence of the health benefits to changes to the built environment, (2) understanding how mosquitoes enter buildings, (3) novel methods for reducing mosquito-house entry, (4) sustainable approaches for reducing mosquito habitats, (5) case studies of micro-financing for healthy homes and (6) methods for increasing scale-up. Multidisciplinary research is essential to build out mosquito-transmitted diseases, and not build them in

Alteration of the embryo transcriptome of hexaploid winter wheat (Triticum aestivum cv. Mercia) during maturation and germination

Grain dormancy and germination are areas of biology that are of considerable interest to the cereal community. We have used a 9,155-feature wheat unigene cDNA microarray resource to investigate changes in the wheat embryo transcriptome during late grain development and maturation and during the first 48 h of postimbibition germination. In the embryo 392 mRNAs accumulated by twofold or greater over the time course from 21 days postanthesis (dpa) to 40 dpa and on through 1 and 2 days postgermination. These included mRNAs encoding proteins involved in amino acid biosynthesis and metabolism, cell division and subsequent cell development, signal transduction, lipid metabolism, energy production, protein turnover, respiration, initiation of transcription, initiation of translation and ribosomal composition. A number of mRNAs encoding proteins of unknown function also accumulated over the time course. Conversely 163 sequences showed decreases of twofold or greater over the time course. A small number of mRNAs also showed rapid accumulation specifically during the first 48 h of germination. We also examined alterations in the accumulation of transcripts encoding proteins involved in abscisic acid signalling. Thus, we describe changes in the level of transcripts encoding wheat Viviparous 1 (Vp1) and other interacting proteins. Interestingly, the transcript encoding wheat Viviparous-interacting protein 1 showed a pattern of accumulation that correlates inversely with germination. Our data suggests that the majority of the transcripts required for germination accumulate in the embryo prior to germination and we discuss the implications of these findings with regard to manipulation of germination in wheat

Human IgG1 Responses to Surface Localised Schistosoma mansoni Ly6 Family Members Drop following Praziquantel Treatment

The heptalaminate-covered, syncytial tegument is an important anatomical adaptation that enables schistosome parasites to maintain long-term, intravascular residence in definitive hosts. Investigation of the proteins present in this surface layer and the immune responses elicited by them during infection is crucial to our understanding of host/parasite interactions. Recent studies have revealed a number of novel tegumental surface proteins including three (SmCD59a, SmCD59b and Sm29) containing uPAR/Ly6 domains (renamed SmLy6A SmLy6B and SmLy6D in this study). While vaccination with SmLy6A (SmCD59a) and SmLy6D (Sm29) induces protective immunity in experimental models, human immunoglobulin responses to representative SmLy6 family members have yet to be thoroughly explored.Using a PSI-BLAST-based search, we present a comprehensive reanalysis of the Schistosoma mansoni Ly6 family (SmLy6A-K). Our examination extends the number of members to eleven (including three novel proteins) and provides strong evidence that the previously identified vaccine candidate Sm29 (renamed SmLy6D) is a unique double uPAR/Ly6 domain-containing representative. Presence of canonical cysteine residues, signal peptides and GPI-anchor sites strongly suggest that all SmLy6 proteins are cell surface-bound. To provide evidence that SmLy6 members are immunogenic in human populations, we report IgG1 (as well as IgG4 and IgE) responses against two surface-bound representatives (SmLy6A and SmLy6B) within a cohort of S. mansoni-infected Ugandan males before and after praziquantel treatment. While pre-treatment IgG1 prevalence for SmLy6A and SmLy6B differs amongst the studied population (7.4% and 25.3% of the cohort, respectively), these values are both higher than IgG1 prevalence (2.7%) for a sub-surface tegumental antigen, SmTAL1. Further, post-treatment IgG1 levels against surface-associated SmLy6A and SmLy6B significantly drop (p = 0.020 and p < 0.001, respectively) when compared to rising IgG1 levels against sub-surface SmTAL1.Collectively, these results expand the number of SmLy6 proteins found within S. mansoni and specifically demonstrate that surface-associated SmLy6A and SmLy6B elicit immunological responses during infection in endemic communities

Killer immunoglobulin-like receptor and human leukocyte antigen-C genotypes in rheumatoid arthritis primary responders and non-responders to anti-TNF-α therapy

The identification of patients who will respond to anti-tumor necrosis factor alpha (anti-TNF-α) therapy will improve the efficacy, safety, and economic impact of these agents. We investigated whether killer cell immunoglobulin-like receptor (KIR) genes are related to response to anti-TNF-α therapy in patients with rheumatoid arthritis (RA). Sixty-four RA patients and 100 healthy controls were genotyped for 16 KIR genes and human leukocyte antigen-C (HLA-C) group 1/2 using polymerase chain reaction sequence-specific oligonucleotide probes (PCR-SSOP). Each patient received anti-TNF-α therapy (adalimumab, etanercept, or infliximab), and clinical responses were evaluated after 3 months using the disease activity score in 28 joints (DAS28). We investigated the correlations between the carriership of KIR genes, HLA-C group 1/2 genes, and clinical data with response to therapy. Patients responding to therapy showed a significantly higher frequency of KIR2DS2/KIR2DL2 (67.7% R vs. 33.3% NR; P = 0.012). A positive clinical outcome was associated with an activating KIR–HLA genotype; KIR2DS2(+)HLA-C group 1/2 homozygous. Inversely, non-response was associated with the relatively inhibitory KIR2DS2(–)HLA-C group 1/2 heterozygous genotype. The KIR and HLA-C genotype of an RA patient may provide predictive information for response to anti-TNF-α therapy

Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012

Observation of associated near-side and away-side long-range correlations in √sNN=5.02 TeV proton-lead collisions with the ATLAS detector

Two-particle correlations in relative azimuthal angle (Δϕ) and pseudorapidity (Δη) are measured in √sNN=5.02  TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1  μb-1 of data as a function of transverse momentum (pT) and the transverse energy (ΣETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Δη|<5) “near-side” (Δϕ∼0) correlation that grows rapidly with increasing ΣETPb. A long-range “away-side” (Δϕ∼π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ΣETPb, is found to match the near-side correlation in magnitude, shape (in Δη and Δϕ) and ΣETPb dependence. The resultant Δϕ correlation is approximately symmetric about π/2, and is consistent with a dominant cos⁡2Δϕ modulation for all ΣETPb ranges and particle pT

Measurement of the cross-section of high transverse momentum vector bosons reconstructed as single jets and studies of jet substructure in pp collisions at √s = 7 TeV with the ATLAS detector

This paper presents a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to all-hadronic final states. The data used in the analysis were recorded by the ATLAS detector at the CERN Large Hadron Collider at a centre-of-mass energy of √s = 7 TeV;{\rm Te}{\rm V}$and correspond to an integrated luminosity of$4.6\;{\rm f}{{{\rm b}}^{-1}}$. The measurement is performed by reconstructing the boosted W or Z bosons in single jets. The reconstructed jet mass is used to identify the W and Z bosons, and a jet substructure method based on energy cluster information in the jet centre-of-mass frame is used to suppress the large multi-jet background. The cross-section for events with a hadronically decaying W or Z boson, with transverse momentum${{p}_{{\rm T}}}\gt 320\;{\rm Ge}{\rm V}$and pseudorapidity$|\eta |\lt 1.9$, is measured to be${{\sigma }_{W+Z}}=8.5\pm 1.7$ pb and is compared to next-to-leading-order calculations. The selected events are further used to study jet grooming techniques

Search for direct pair production of the top squark in all-hadronic final states in proton-proton collisions at s√=8 TeV with the ATLAS detector

The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of 20.1fb−1 of proton–proton collision data at √s = 8 TeV recorded with the ATLAS detector at the LHC are reported. The top squark is assumed to decay via t˜→tχ˜01 or t˜→ bχ˜±1 →bW(∗)χ˜01 , where χ˜01 (χ˜±1 ) denotes the lightest neutralino (chargino) in supersymmetric models. The search targets a fully-hadronic final state in events with four or more jets and large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits are reported in terms of the top squark and neutralino masses and as a function of the branching fraction of t˜ → tχ˜01 . For a branching fraction of 100%, top squark masses in the range 270–645 GeV are excluded for χ˜01 masses below 30 GeV. For a branching fraction of 50% to either t˜ → tχ˜01 or t˜ → bχ˜±1 , and assuming the χ˜±1 mass to be twice the χ˜01 mass, top squark masses in the range 250–550 GeV are excluded for χ˜01 masses below 60 GeV