2,220 research outputs found

    Energy Allocation in Ephemeral Adult Insects

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    Author Institution: Department of Entomology, University of IllinoisEphemeral adults must be structurally prepared to produce a certain number of progeny, because time of reproduction is not a maneuverable factor. Since structures are more visible than fecundity, reproductive strategies may be more easily studied and interpreted. A study of 10 species of parasitic wasps (Hymenoptera: Ichneumonidae), with ephemeral adults (longevity 13-31 days with only one or two generations per year), used ovariole numbers per ovary, egg volume and number, and the survivorship curve of the host, and host stage attacked, was used to interpret reproductive strategies. The balanced mortality hypothesis and Lack's hypothesis are supported. There is an evolutionary trend in the family Ichneumonidae for increased egg production paralleled by a decreased total reproductive effor

    Metal-assisted reactions. Part 25. Heterogeneous and homogeneous catalytic transfer hydrogenolysis of allyloxytetrazoles to yield alkenes or alkanes

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    Transfer hydrogenolysis of 5-allyloxy- 1-phenyltetrazoles using either a heterogeneous or a homogeneous palladium catalyst and a hydrogen donor leads to cleavage of the allyloxy C-O bond to yield an alkane or an alkene and 1-phenyltetrazolone, depending on the catalyst used

    Adaptive radiation into ecological niches with eruptive dynamics: a comparison of tenthredinid and diprionid sawflies

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    Summary 1. We tested the hypothesis that the bottom-up influence of coniferous plant resources promotes the probability of outbreak or eruptive dynamics in sawflies. The literature was examined for three geographical regions − North America north of Mexico, Europe and Japan. 2. In each region tenthredinid sawflies (Hymenoptera: Tenthredinidae) were significantly more likely to be eruptive on conifers than on angiosperms. 3. The diprionid sawflies (Hymenoptera: Diprionidae) that attack conifers exclusively showed a significantly higher probability of eruptive dynamics than the tenthredinid sawflies on angiosperms in two regions, North America and Europe, and in Japan the trend was in the same direction. 4. The probability of species showing eruptive dynamics on coniferous hosts was not significantly different among tenthredinids and diprionids on conifers in North America, Europe and Japan. 5. The weight of evidence supports the hypothesis of conifers supporting a higher percentage of eruptive species than angiosperms. 6. In the adaptive radiation of tenthredinid sawflies from flowering plants onto conifers, larches ( Larix ) appear to be particularly favourable for colonization, but pines ( Pinus ) have not been colonized in any region, a pattern likely to be explained by the growth characteristics of the host plants. 7. Among tenthredinid species in Europe, where sawfly/host relationships are best known, there is a significant trend for an increasing proportion of outbreaking species from herbs, to shrubs, to trees. 8. The results indicate for the first time the strong bottom-up effects of plant resources on the population dynamics of sawflies, involving general features of host plant taxa and growth characteristics

    Adaptive radiation into ecological niches with eruptive dynamics: a comparison of tenthredinid and diprionid sawflies

    Get PDF
    Summary 1. We tested the hypothesis that the bottom-up influence of coniferous plant resources promotes the probability of outbreak or eruptive dynamics in sawflies. The literature was examined for three geographical regions − North America north of Mexico, Europe and Japan. 2. In each region tenthredinid sawflies (Hymenoptera: Tenthredinidae) were significantly more likely to be eruptive on conifers than on angiosperms. 3. The diprionid sawflies (Hymenoptera: Diprionidae) that attack conifers exclusively showed a significantly higher probability of eruptive dynamics than the tenthredinid sawflies on angiosperms in two regions, North America and Europe, and in Japan the trend was in the same direction. 4. The probability of species showing eruptive dynamics on coniferous hosts was not significantly different among tenthredinids and diprionids on conifers in North America, Europe and Japan. 5. The weight of evidence supports the hypothesis of conifers supporting a higher percentage of eruptive species than angiosperms. 6. In the adaptive radiation of tenthredinid sawflies from flowering plants onto conifers, larches ( Larix ) appear to be particularly favourable for colonization, but pines ( Pinus ) have not been colonized in any region, a pattern likely to be explained by the growth characteristics of the host plants. 7. Among tenthredinid species in Europe, where sawfly/host relationships are best known, there is a significant trend for an increasing proportion of outbreaking species from herbs, to shrubs, to trees. 8. The results indicate for the first time the strong bottom-up effects of plant resources on the population dynamics of sawflies, involving general features of host plant taxa and growth characteristics

    Diverse population trajectories among coexisting species of subarctic forest moths

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    Records of 232 moth species spanning 26 years (total catch of ca. 230,000 specimens), obtained by continuous light‐trapping in Kevo, northernmost subarctic Finland, were used to examine the hypothesis that life‐history traits and taxonomic position contribute to both relative abundance and temporal variability of Lepidoptera. Species with detritophagous or moss‐feeding larvae, species hibernating in the larval stage, and species pupating during the first half of the growing season were over‐represented among 42 species classified as abundant during the entire sampling period. The coefficients of variation in annual catches of species hibernating as eggs averaged 1.7 times higher than those of species hibernating as larvae or pupae. Time‐series analysis demonstrated that periodicity in fluctuations of annual catches is generally independent of life‐history traits and taxonomic affinities of the species. Moreover, closely related species with similar life‐history traits often show different population dynamics, undermining the phylogenetic constraints hypothesis. Species with the shortest (1 year) time lag in the action of negative feedback processes on population growth exhibit the largest magnitude of fluctuations. Our analyses revealed that only a few consistent patterns in the population dynamics of herbivorous moths can be deduced from life‐history characteristics of the species. Moreover, the diversity of population behaviour in one moth assemblage challenges any conventional wisdom suggesting predictable patterns. Our results raise several questions about perceptions and paradigms in insect population dynamics and stress the need for research on detritivorous insect population dynamics, as well as the need for more assemblage‐wide studies using common trapping methods to provide comparative data on related and unrelated species with different life‐history traits.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146872/1/pope0295.pd

    Supervoid Origin of the Cold Spot in the Cosmic Microwave Background

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    We use a WISE-2MASS-Pan-STARRS1 galaxy catalog to search for a supervoid in the direction of the Cosmic Microwave Background Cold Spot. We obtain photometric redshifts using our multicolor data set to create a tomographic map of the galaxy distribution. The radial density profile centred on the Cold Spot shows a large low density region, extending over 10's of degrees. Motivated by previous Cosmic Microwave Background results, we test for underdensities within two angular radii, 5∘5^\circ, and 15∘15^\circ. Our data, combined with an earlier measurement by Granett et al 2010, are consistent with a large Rvoid=(192±15)h−1MpcR_{\rm void}=(192 \pm 15)h^{-1} Mpc (2σ)(2\sigma) supervoid with ή≃−0.13±0.03\delta \simeq -0.13 \pm 0.03 centered at z=0.22±0.01z=0.22\pm0.01. Such a supervoid, constituting a ∌3.5σ\sim3.5 \sigma fluctuation in the ΛCDM\Lambda CDM model, is a plausible cause for the Cold Spot.Comment: 4 pages, 2 figures, Proceedings of IAU 306 Symposium: Statistical Challenges in 21st Century Cosmolog

    The Collision of Two Black Holes

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    We study the head-on collision of two equal mass, nonrotating black holes. We consider a range of cases from holes surrounded by a common horizon to holes initially separated by about 20M20M, where MM is the mass of each hole. We determine the waveforms and energies radiated for both the ℓ=2\ell = 2 and ℓ=4\ell=4 waves resulting from the collision. In all cases studied the normal modes of the final black hole dominate the spectrum. We also estimate analytically the total gravitational radiation emitted, taking into account the tidal heating of horizons using the membrane paradigm, and other effects. For the first time we are able to compare analytic calculations, black hole perturbation theory, and strong field, nonlinear numerical calculations for this problem, and we find excellent agreement.Comment: 14 pages, 93-
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