69 research outputs found

    Endogenous popularity: how perceptions of support affect the popularity of authoritarian regimes

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    Being popular makes it easier for dictators to govern. A growing body of scholarship therefore focuses on the factors that influence authoritarian popularity. However, it is possible that the perception of popularity itself affects incumbent approval in autocracies. We use framing experiments embedded in four surveys in Russia to examine this phenomenon. These experiments reveal that manipulating information - and thereby perceptions - about Russian President Vladimir Putin's popularity can significantly affect respondents' support for him. Additional analyses, which rely on a novel combination of framing and list experiments, indicate that these changes in support are not due to preference falsification, but are in fact genuine. This study has implications for research on support for authoritarian leaders and defection cascades in nondemocratic regimes

    Natal and Breeding Dispersal of Bobolinks (Dolichonyx Oryzivorus) And Savannah Sparrows (Passerculus Sandwichensis) In An Agricultural Landscape

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    Dispersal is a key process in the metapopulation dynamics and genetic structure of spatially segregated populations. However, our knowledge of avian dispersal, particularly in migratory passerines, remains limited. We studied dispersal of Bobolinks (Dolichonyx oryzivorus) and Savannah Sparrows (Passerculus sandwichensis) to determine whether agricultural management practices affected dispersal patterns and habitat selection. From 2002 to 2006, we banded adults and nestlings on six focal hay fields and two pastures in the Champlain Valley of Vermont and New York and searched for banded birds within 1.5 km of Vermont field sites during two years. Natal dispersal distances were greater than breeding dispersal in both species, and breeding dispersal distances of Bobolinks were greater than those of Savannah Sparrows. Site fidelity was high in both species, with \u3e80% of detected adults and ~30% of detected natal dispersers returning to the same field in subsequent years. During natal dispersal, movement was random with respect to habitat quality. Adult Bobolinks dispersed to fields with annual reproductive rates greater than or equal to those of their original field; by contrast, adult Savannah Sparrows were more likely to move to or remain in low-quality habitats. During breeding dispersal, strong site fidelity took precedence over the effect of the previous year’s nest success on the probability of dispersal, particularly for Savannah Sparrows. Site fidelity has implications for management of agricultural fields because consistency of cropping patterns and cutting dates are important for maintaining populations of these species

    Grassland Songbird Survival And Recruitment In Agricultural Landscapes: Implications For Source-Sink Demography

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    Population growth and decline are particularly sensitive to changes in three key life-history parameters: annual productivity, juvenile survival, and adult survival. However, for many species these parameters remain unknown. For example, although grassland songbirds are imperiled throughout North America, for this guild, only a small number of studies have assessed these parameters. From 2002 to 2006, in the agricultural landscape of the Champlain Valley of Vermont and New York, USA, we studied Savannah Sparrow (Passerculus sandwichensis) and Bobolink (Dolichonyx oryzivorus) demography on four grassland treatments: (1) early-hayed fields cut before 11 June and again in early- to mid-July; (2) middle-hayed fields cut once between 21 June and 10 July; (3) late-hayed fields cut after 1 August; and (4) rotationally grazed pastures. We assessed whether these treatments affected adult apparent survival (φ) and recruitment (ƒ ), how sensitive these parameters were to the presence of nonbreeders and local dispersal, and the populations’ ability to persist in these four habitats. On average, birds using late-hayed fields had \u3e25% higher apparent survival than those on the more intensively managed early-hayed, middle-hayed, and grazed fields. Overall male φ was 35% higher than female φ, and Savannah Sparrow φ was 44% higher than Bobolink φ. Across all analyses and treatments, apparent survival estimates were 0.58–0.85 for male and 0.48–0.71 for female Savannah Sparrows, and 0.52–0.70 for male and 0.19–0.55 for female Bobolinks. For males of both species, potential nonbreeders decreased the precision of and lowered apparent survival estimates by 25%; female estimates showed little variation with the inclusion of nonbreeders. Inclusion of local dispersal observations increased apparent survival estimates and, in many cases, increased precision, though the effect was stronger for Savannah Sparrows than for Bobolinks, and also stronger for males than for females. High Savannah Sparrow apparent survival rates resulted in stable or near stable populations (λ ≈ 1), particularly in late-hayed and grazed fields, while low Bobolink apparent survival rates resulted in strongly declining populations (λ \u3c 1) in all treatments

    Grassland Songbirds In A Dynamic Management Landscape: Behavioral Responses And Management Strategies

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    In recent decades, earlier and more frequent harvests of agricultural grasslands have been implicated as a major cause of population declines in grassland songbirds. From 2002 to 2005, in the Champlain Valley of Vermont and New York, USA, we studied the reproductive success of Savannah Sparrows (Passerculus sandwichensis) and Bobolinks (Dolichonyx oryzivorus) on four grassland treatments: (1) early-hayed fields cut before 11 June and again in early- to mid-July; (2) middle-hayed fields cut once between 21 June and 10 July; (3) late-hayed fields cut after 1 August; and (4) rotationally grazed pastures. Both the number of fledglings per female per year and nest success (logistic-exposure method) varied among treatments and between species. Although birds initiated nests earlier on early-hayed fields compared to others, haying caused 99% of active Savannah Sparrow and 100% of active Bobolink nests to fail. Both the initial cutting date and time between cuttings influenced renesting behavior. After haying, Savannah Sparrows generally remained on early-hayed fields and immediately renested (clutch completion 15.6 ± 1.28 days post-haying; all values are reported as mean 6 SE), while Bobolinks abandoned the fields for at least two weeks (mean clutch completion 33 ± 0.82 days post-haying). While female Savannah Sparrows fledged more offspring per year (1.28 ± 0.16) than female Bobolinks (0.05 6 0.05), reproductive success on early-hayed fields was low. The number of fledglings per female per year was greater on middle-hayed fields (Savannah Sparrows, 3.47 ± 0.42; Bobolinks, 2.22 ± 0.26), and late-hayed fields (Savannah Sparrows, 3.29 ± 0.30; Bobolinks, 2.79 ± 0.18). Reproductive success was moderate on rotationally grazed pastures, where female Savannah Sparrows and female Bobolinks produced 2.32 ± 0.25 and 1.79 ± 0.33 fledgling per year, respectively. We simultaneously conducted cutting surveys throughout the Champlain Valley and found that 3–8% of hayfield habitat was cut by 1–4 June, 25–40% by 12–16 June, and 32–60% by 28 June–2 July. Thus, the majority of grassland habitat was cut during the breeding season; however, late-hayed fields served as high-quality reserves for late-nesting female Bobolinks that were displaced from previously hayed fields. For fields first cut in May, a 65-day interval between cuts could provide enough time for both species to successfully fledge young

    Development of a gene silencing DNA vector derived from a broad host range geminivirus

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    <p>Abstract</p> <p>Background</p> <p>Gene silencing is proving to be a powerful tool for genetic, developmental, and physiological analyses. The use of viral induced gene silencing (VIGS) offers advantages to transgenic approaches as it can be potentially applied to non-model systems for which transgenic techniques are not readily available. However, many VIGS vectors are derived from Gemini viruses that have limited host ranges. We present a new, unipartite vector that is derived from a curtovirus that has a broad host range and will be amenable to use in many non-model systems.</p> <p>Results</p> <p>The construction of a gene silencing vector derived from the geminivirus <it>Beet curly top virus </it>(BCTV), named pWSRi, is reported. Two versions of the vector have been developed to allow application by biolistic techniques or by agro-infiltration. We demonstrate its ability to silence nuclear genes including ribulose bisphosphate carboxylase small subunit (<it>rbcS</it>), <it>transketolase</it>, the sulfur allele of magnesium chelatase (<it>ChlI</it>), and two homeotic transcription factors in spinach or tomato by generating gene-specific knock-down phenotypes. Onset of phenotypes occurred 3 to 12 weeks post-inoculation, depending on the target gene, in organs that developed after the application. The vector lacks movement genes and we found no evidence for significant spread from the site of inoculation. However, viral amplification in inoculated tissue was detected and is necessary for systemic silencing, suggesting that signals generated from active viral replicons are efficiently transported within the plant.</p> <p>Conclusion</p> <p>The unique properties of the pWSRi vector, the ability to silence genes in meristem tissue, the separation of virus and silencing phenotypes, and the broad natural host range of BCTV, suggest that it will have wide utility.</p

    Determining the extragalactic extinction law with SALT. II. Additional sample

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    We present new results from an on-going programme to study the dust extragalactic extinction law in E/S0 galaxies with dust lanes with the Southern African Large Telescope (SALT) during its performance-verification phase. The wavelength dependence of the dust extinction for seven galaxies is derived in six spectral bands ranging from the near-ultraviolet atmospheric cutoff to the near-infrared. The derivation of an extinction law is performed by fitting model galaxies to the unextinguished parts of the image in each spectral band, and subtracting from these the actual images. We compare our results with the derived extinction law in the Galaxy and find them to run parallel to the Galactic extinction curve with a mean total-to-selective extinction value of 2.71+-0.43. We use total optical extinction values to estimate the dust mass for each galaxy, compare these with dust masses derived from IRAS measurements, and find them to range from 10^4 to 10^7 Solar masses. We study the case of the well-known dust-lane galaxy NGC2685 for which HST/WFPC2 data is available to test the dust distribution on different scales. Our results imply a scale-free dust distribution across the dust lanes, at least within ~1 arcsec (~60 pc) regions.Comment: 11 pages, 7 figures, 3 tables. Accepted for publication in MNRAS. R-band contour maps and B-R colour-index maps are low-resolution versions of those used in the MNRAS versio

    Approaches for advancing scientific understanding of macrosystems

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    The emergence of macrosystems ecology (MSE), which focuses on regional- to continental-scale ecological patterns and processes, builds upon a history of long-term and broad-scale studies in ecology. Scientists face the difficulty of integrating the many elements that make up macrosystems, which consist of hierarchical processes at interacting spatial and temporal scales. Researchers must also identify the most relevant scales and variables to be considered, the required data resources, and the appropriate study design to provide the proper inferences. The large volumes of multi-thematic data often associated with macrosystem studies typically require validation, standardization, and assimilation. Finally, analytical approaches need to describe how cross-scale and hierarchical dynamics and interactions relate to macroscale phenomena. Here, we elaborate on some key methodological challenges of MSE research and discuss existing and novel approaches to meet them

    Determining the extragalactic extinction law with SALT

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    We present CCD imaging observations of early-type galaxies with dark lanes obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. We derive the extinction law by the extragalactic dust in the dark lanes in the spectral range 1.11mu m^{-1} < lambda^{-1} < 2.94 mu m^{-1} by fitting model galaxies to the unextinguished parts of the image, and subtracting from these the actual images. We find that the extinction curves run parallel to the Galactic extinction curve, which implies that the properties of dust in the extragalactic enviroment are similar to those of the Milky Way. The ratio of the total V band extinction to the selective extinction between the V and B bands is derived for each galaxy with an average of 2.82+-0.38, compared to a canonical value of 3.1 for the Milky Way. The similar values imply that galaxies with well-defined dark lanes have characteristic dust grain sizes similar to those of Galactic dust.Comment: 20 pages, 15 figures and 4 tables. Accepted for publication in MNRA
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