Intraspecific variation in the strength of density dependence in aphid populations

Abstract. 1. Experimental evidence is presented for positive, negative, and no density dependence from 32 independent density manipulations of milkweed aphids (Aphis nerii) in laboratory and field experiments. This substantial variation in intraspecific density dependence is associated with temperature and host-plant species. 2. It is reported that as population growth rate increases, density dependence becomes more strongly negative, suggesting that the monotonic definition of density dependence used in many common population models is appropriate for these aphids, and that population growth rate and carrying capacity are not directly proportional. 3. For populations that conform to these assumptions, population growth rate may be widely applicable as a predictor of the strength of density dependence

Phylogeography of spruce beetles ( Dendroctonus rufipennis Kirby) (Curculionidae: Scolytinae) in North America

Abstract Tree-feeding insects that are widespread in north temperate regions are excellent models for studying how past glaciations have impacted differentiation and speciation. We used mitochondrial DNA (mtDNA) sequences and allele frequencies at nine microsatellite loci to examine genetic population structure across the current range of the spruce beetle ( Dendroctonus rufipennis ), an economically important insect in North America. Two major haplotype groups occur across northern North America, from Newfoundland to Alaska, on white spruce ( Picea glauca ), and a third distinctive haplotype group occurs throughout the Rocky Mountains on Engelmann spruce ( Picea engelmannii ). The two mtDNA lineages found in northern populations are 3 -4% divergent from each other and from the lineages found in the Rocky Mountains. Analyses of microsatellite data also suggest the existence of major population groupings associated with different geographical regions. In the Pacific Northwest, concordant contact zones for genetically distinct populations of spruce beetles and their principal hosts appear to reflect recent secondary contact. Although we could detect no evidence of historical mtDNA gene flow between allopatric population groups, patterns of variation in the Pacific Northwest suggest recent hybridization and introgression. Together with the pollen record for spruce, they also suggest that beetles have spread from at least three glacial refugia. A minimum estimate of divergence time between the Rocky Mountain and northern populations was 1.7 Myr (million years), presumably reflecting the combined effects of isolation during multiple glacial cycles

Genome-wide linkage scan in affected sibling pairs identifies novel susceptibility region for venous thromboembolism: Genetics In Familial Thrombosis study

To cite this article: de Visser MCH, van Minkelen R, van Marion V, den Heijer M, Eikenboom J, Vos HL, Slagboom PE, Houwing-Duistermaat JJ, Rosendaal FR, Bertina RM. Genome-wide linkage scan in affected sibling pairs identifies novel susceptibility region for venous thromboembolism: Genetics in Familial Thrombosis study. J Thromb Haemost 2013; 11: 1474-84. Summary. Background: Venous thromboembolism (VTE) is a multicausal disorder involving environmental and genetic risk factors. In many thrombophilic families the clustering of thrombotic events cannot be explained by known genetic risk factors, indicating that some remain to be discovered. Objectives: We aimed to identify novel thrombosis susceptibility alleles in a large panel of small thrombophilic families: the Genetics In Familial Thrombosis (GIFT) study. Patients/Methods: In the GIFT study, 201 families were recruited consisting of 438 siblings with an objectively confirmed VTE at a young age. Multipoint linkage analysis (402 SSR markers) and fine mapping were performed, followed by genotyping of tagging SNPs in positional candidate genes. Results: Established genetic risk factors such as factor V Leiden, ABO blood group non-O, prothrombin 20210A, fibrinogen gamma 10034T and deficiencies of antithrombin, protein C and protein S were more frequent in GIFT patients than in unselected VTE patients. Linkage supported the presence of novel thrombosis susceptibility loci on 7p21.3-22.2 (LOD score = 3.23) and Xq24-27.3 (LOD score = 1.95). Simulation analysis showed that the chr7 signal was genome-wide statistically significant (P = 0.022). Tagging SNPs (n = 157) in eight positional candidate genes (LOD drop 1.5 regions) were genotyped in GIFT patients and 332 healthy controls. Five chr7 SNPs associated with VTE. SNP THSD7A rs2074597 was responsible for part of the chr7 signal. Conclusions: The GIFT panel is rich in established genetic risk factors for VTE, but genetic factors remain unidentified in many families. Genome-wide linkage failed to identify the previously established genetic risk factors for VTE, but identified a novel VTE susceptibility locus on chr7

Reproductive skew and relatedness in social groups of European badgers, Meles meles

Abstract Reproductive skew is a measure of the proportion of individuals of each sex that breed in a group and is a valuable measure for understanding the evolution and maintenance of sociality. Here, we provide the first quantification of reproductive skew within social groups of European badgers Meles meles, throughout an 18-year study in a high-density population. We used 22 microsatellite loci to analyse within-group relatedness and demonstrated that badger groups contained relatives. The average within-group relatedness was high (R = 0.20) and approximately one-third of within-group dyads were more likely to represent first-order kin than unrelated pairs. Adult females within groups had higher pairwise relatedness than adult males, due to the high frequency of extra-group paternities, rather than permanent physical dispersal. Spatial clustering of relatives occurred among neighbouring groups, which we suggest was due to the majority of extra-group paternities being attributable to neighbouring males. Reproductive skew was found among withingroup candidate fathers (B = 0.26) and candidate mothers (B = 0.07), but not among breeding individuals; our power to detect skew in the latter was low. We use these results to evaluate reproductive skew models. Although badger society best fits the assumptions of the incomplete-control models, our results were not consistent with their predictions. We suggest that this may be due to female control of paternity, female-female reproductive suppression occurring only in years with high food availability resulting in competition over access to breeding sites, extra-group paternity masking the benefits of natal philopatry, and/or the inconsistent occurrence of hierarchies that are linear when established

Highly Dispersive Spin Excitations in the Chain Cuprate Li2CuO2

We present an inelastic neutron scattering investigation of Li2CuO2 detecting the long sought quasi-1D magnetic excitations with a large dispersion along the CuO2-chains studied up to 25 meV. The total dispersion is governed by a surprisingly large ferromagnetic (FM) nearest-neighbor exchange integral J1=-228 K. An anomalous quartic dispersion near the zone center and a pronounced minimum near (0,0.11,0.5) r.l.u. (corresponding to a spiral excitation with a pitch angle about 41 degree point to the vicinity of a 3D FM-spiral critical point. The leading exchange couplings are obtained applying standard linear spin-wave theory. The 2nd neighbor inter-chain interaction suppresses a spiral state and drives the FM in-chain ordering below the Ne'el temperature. The obtained exchange parameters are in agreement with the results for a realistic five-band extended Hubbard Cu 3d O 2p model and L(S)DA+U predictions.Comment: 6 pages, 4 figures, submitted to Europhys. Let

Microsatellite markers for the grapevine pathogen, Eutypa lata

Abstract We isolated and characterized nine polymorphic microsatellite markers for Eutypa lata, a fungal pathogen responsible for Eutypa dieback of grapevine, in populations from two California vineyards (24 isolates per vineyard). Allele frequency ranged from two to 11 alleles per locus and haploid gene diversity ranged from 0.33 to 0.83. All samples comprised unique haplotypes. Our results suggest that there is sufficient allelic polymorphism to estimate fine-scale spatial structure, and to identify possible sources of inoculum from habitats outside of vineyards. Keywords: Ascomycota, Diatrypaceae, Eutypa dieback, Eutypa lata, plant pathogen, Vitis vinifera Received 19 May 2008; revision accepted 10 June 2008 The means of spread of Eutypa dieback from vine-to-vine within vineyards is likely due to dispersal of Eutypa lata sexual spores (ascospores), and not asexual spores (conidia), based on evidence of distributions of vegetative compatibility groups, reproductive structures (perithecia), and symptomatic grapevines Genomic DNA was extracted from an isolate of E. lata from Switzerland [isolate 208.87; Centraalbureau voor Schimmelcultures, Utrecht, the Netherlands], purified (GENECLEAN III Kit, MP Biomedicals), digested with Taq αI (New England BioLabs), and enriched for both a trinucleotide, CAC 10 , and a tetranucleotide mixture (AAAC 6 , AAAG 6 , AAAT 8 , AGAT 8 ; Integrated DNA Technologies). Digested DNA was ligated to linker oligonucleotides 20B (5′-GCGGTTCCCGGTCGAGTTGG-3′) and 22B (5′-pCGCCAACTCGACCGGGAACCGC-3′

Many pion decays of rho(770) and omega(782) mesons in chiral theory

The decays rho(770) to 4 pi and omega(782) to 5pi are considered in detail in the approach based on the Weinberg Lagrangian obtained upon the nonlinear realization of chiral symmetry, added with the term induced by the anomalous Lagrangian of Wess and Zumino. The partial widths and excitation curves of the decays rho^0 to 2 pi^+ 2 pi^-, pi^+ pi^- 2 pi^0, rho^{+-} to 2 pi^{+-} pi^{-+} pi^0, rho^(+-} to pi^(+-} 3 pi^0 are evaluated for e^+e^- annihilation, photoproduction and tau lepton decays. The results of calculations are compared with the recent CMD-2 data on the decay rho^0 to 2 pi^+ 2 pi^- observed in e^+e^- annihilation. The omega to 5 pi decay widths and excitation curves in e^+e^- annihilation are obtained. The angular distributions for various combinations of the final pions in the decays rho to 4 pi and omega to 5 pi are written. The perspectives of the experimental study of the above decays in e^+e^- annihilation, tau lepton decays and photoproduction are discussed.Comment: Revtex, 32 pages including 11 ps figures. Replaced to fit the version published in Phys. Rev. D. Material rearranged, clarifying remarks and references added, typos fixe

Exact Results for the Crossover from Gaussian to Non-Gaussian Order Parameter Fluctuations in Quasi One-Dimensional Electronic Systems

The physics of quasi one-dimensional Peierls systems is dominated by order parameter fluctuations. We present an algorithm which allows for the first time to exactly calculate physical properties of the electrons gas coupled to classical order parameter fluctuations. The whole range from the Gaussian regime dominated by amplitude fluctuations to the non-Gaussian regime dominated by phase fluctuations is accessible. Our results provide insight into the 'pseudogap' phenomenon occurring in underdoped high-temperature superconductors, quasi one-dimensional organic conductors and liquid metals.Comment: 4 pages, 4 figures, accepted for publication in Physical Review Letter

Determination of the pion-nucleon coupling constant and scattering lengths

We critically evaluate the isovector GMO sum rule for forward pion-nucleon scattering using the recent precision measurements of negatively charged pion-proton and pion-deuteron scattering lengths from pionic atoms. We deduce the charged-pion-nucleon coupling constant, with careful attention to systematic and statistical uncertainties. This determination gives, directly from data a pseudoscalar coupling constant of 14.11+-0.05(statistical)+-0.19(systematic) or a pseudovector one of 0.0783(11). This value is intermediate between that of indirect methods and the direct determination from backward neutron-proton differential scattering cross sections. We also use the pionic atom data to deduce the coherent symmetric and antisymmetric sums of the negatively charged pion-proton and pion-neutron scattering lengths with high precision. The symmetric sum gives 0.0012+-0.0002(statistical)+-0.0008 (systematic) and the antisymmetric one 0.0895+-0.0003(statistical)+-0.0013(systematic), both in units of inverse charged pion-mass. For the need of the present analysis, we improve the theoretical description of the pion-deuteron scattering length.Comment: 27 pages, 5 figures, submitted to Phys. Rev. C, few modifications and clarifications, no change in substance of the pape

Radiative decays of decuplet hyperons

We calculate the radiative decay widths of decuplet hyperons in a chiral constituent quark model including electromagnetic exchange currents between quarks. Exchange currents contribute significantly to the E2 transition amplitude, while they largely cancel for the M1 transition amplitude. Strangeness suppression of the radiative hyperon decays is found to be weakened by exchange currents. Differences and similarities between our results and other recent model predictions are discussed.Comment: 11 pages, 1 eps figure, revtex, accepted for publication in Phys. Rev.