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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 104 (1995), S. 12-16 
    ISSN: 1432-1939
    Keywords: Mellitochory ; Seed dispersal ; Stingless bees ; Eucalyptus torelliana ; Trigona carbonaria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ants are the only group of invertebrates currently identified as significant dispersers of seeds, but we report here the dispersal of Eucalyptus torelliana seeds by bees. Fruits of E. torelliana produce resin which is collected by workers of the stingless bee Trigona carbonaria. Seeds adhere to resin in the workers' corbiculate and are transported to the nest. Workers transported seeds distances of more than 300 m from the parent tree and seeds at the nest were viable and capable of germination. Seeds were removed from the nests by workers and discarded away from the nest, and E. torelliana trees became established in the vicinity of colonies of T. carbonaria. ‘Mellitochory’ may be a novel method of seed dispersal where bees are dispersers, and associated with fruits that produce resin as an attractant for bees.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 12 (1973), S. 315-327 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Population fluctuation patterns were determined during 1959–70 in wheat bulks in 2 granaries typical of those used on Manitoba farms for 7 kinds of mites. The patterns were bradly similar in the 2 granaries. Outbreaks of all mites except Tarsonemus granarius and Aëroglyphus robustus were unaffected by the prolonged storage of grain; those of Acarus siro and Cheyletus eruditus occurred in unusually high numbers periodically every 2–5 years, whereas Glycyphagus destructor and Androlaelaps casalis were present in relatively low numbers from the first year of storage. A rise in T. granarius population corresponded with grain age and the succession of microfloral species. Tydeid mites occurred periodically. Pricipal component analyses of up to 26 variates including various fungal species on one grain bulk ecosystem provided a “kaleidoscopic” view of interrelations and dynamics of acarine populations in the grain bulks. The combination of correlated variates of which mites are a part, varied from year to year. Four factors that regulate acarine numbers, particularly those of A. siro and its natural predator C. eruditus, were identified. These are: (i) basic determinants (moisture, temperature, food, and the intrinsic rate of increase of the species); (ii) the main regulator (temperature); (iii) influencers (seed cracks, microflora, dockage, etc.); and (iv) seasonal and cyclic regulators (seasonality in temperature and several density-dependent factors). Generalized diagrams of prey-predator interactions and multivariate interrelations of each kind of mite are presented.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 74 (1987), S. 31-38 
    ISSN: 1432-1939
    Keywords: Fecundity-perennial herb ; Flower bud abortion ; Seed survivorship ; Inbreeding ; Epilobium montanum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plants of the inbreeding perennial herb Epilobium montanum L. were defoliated at two stages in development and the formation and abortion of flower buds, flowers, copsules and ovules was compared with control plants. A comparison was also made of the effects of self- and cross-pollination on fecundily. Defoliation reduced the number of flower buds formed but its greatest effect was to increase the abortion of flower buds. Defoliation also caused earlier abortions which were generally lower on the racemes of the treated than on the control plants. The abortion of flowers and capsules was much less significant. The number of ovules formed per capsule decreased with height on the raceme and the abortion rate of ovules was increased by defoliation. The pattern of ovule abortion within the capsules differed between cross- and self-pollinated plants but the number of seeds ripened was not affected. The overall survivorship of ovules to mature seeds was 89.3% which compares with the average of 85% found by Wiens for inbreeding annuals. The findings suggest that such high values of ovule survivorship may be characteristics of normally inbreeding species irrespective of whether they are annuals or perennials.
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  • 4
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The impact of insect infestation on several biotic and abiotic variates in 3 small bulk-wheat ecosystems was studied by measuring these variates at monthly intervals during 1969–1970. One ecosystem was insect-free, the second was artificially infested with Cryptolestes ferrugineus and Oryzaephilus surinamensis, and the third with Sitophilus granarius and Tribolium castaneum. The relationships between 8 environmental and 8 entomological and microbial variates were examined by canonical correlation analyses. The degree of predictability (R c 2 ) of the first pair of canonical variates in the 3 ecosystems ranged from 80% to 95%. The first 2 pairs of canonical variates were highly significant in all 3 analyses (P〈0.01). In the insect-free ecosystems the canonical variates revealed that temperature and the period of storage were the primary environmental antecedents involved and the criterion was composed primarily of the field fungus Alternaria and the storage fungus Aspergillus. In the second ecosystem uric acid level in the grain bulk was an additional environmental factor that affected the population of both species of insects and 3 kinds of fungi Altrnaria, Aspergillus, and Penicillium. In the third ecosystem temperature, time, uric acid and moisture interacted collectively, with density of insect populations, reduction of Alternaria, and increase of Aspergillus.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 34 (1978), S. 1360-1361 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Contrary to the predictions of the clockface model, rotating a regenerate by 90° produces duplications identical to those resulting from 180° axial reversals. Exchanging regenerates between arms indicates the presence of 2 determined transverse axes.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 55 (1999), S. 901-909 
    ISSN: 1420-9071
    Keywords: Key words. Sex determination; sex reversal; temperature dependence; sex hormone; amphibia; Triturus cristatus.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Amphibians employ a genetic mechanism of sex determination, according to all available information on sex chromosomes or breeding tests. Sex reversal allows breeding tests to establish which sex is heterogametic and provides an indication of the mechanism of sex determination. Cases of spontaneous and experimental sex reversal (by temperature, hormones or surgery) are reviewed and illustrated by previously unpublished studies on crested newts. These newts respond conventionally to temperature and hormone treatment but provide anomalous results from breeding tests. It is suggested that both the evolution from temperature dependency to a genetic switch and from ZZ/ZW to XX/XY are superimposed on a generally uniform mechanism of sex determination in all vertebrates.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 40 (1984), S. 985-986 
    ISSN: 1420-9071
    Keywords: Axolotl ; Ambystoma mexicanum ; limb regeneration ; regeneration ; limb ; vitamin A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Axolotl forearms isolated from upper arm tissue either surgically or by local irradiation regenerate excessive structures after vitamin A treatment. This demonstration excludes the possibility of regeneration being altered by enhanced cellular migration and thus indicates that vitamin A respecifies cells close to the site of amputation.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 134 (1990), S. 541-557 
    ISSN: 1420-9136
    Keywords: Magnetosphere ; ring current ; Dst index ; earth conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Two current rings have been observed in the equatorial plane of the earth at times of high geomagnetic activity. An eastward current exists between about 2 and 3.5 earth radii (Re) distant, and a larger, more variable companion current exists between about 4 and 9 Re. These current regions are loaded during geomagnetic substorms. They decay, almost exponentially, after the cessation of the particle influx that attends the solar wind disturbance. This review focuses upon characteristics needed for intelligent use of the ring current as a source for induction probing of the earth's mantle. Considerable difficulties are found with the assumption thatDst is a ring-current index.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 125 (1987), S. 193-204 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 125 (1987), S. 427-457 
    ISSN: 1420-9136
    Keywords: Electric conductivity ; upper mantle ; Sq ; geomagnetic daily variations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The electrical conductivity of the Earth's upper mantle can be inferred from geomagnetic quiet-day,Sq, variations recorded at the world's observatories using the, coefficients of a spherical harmonic analysis (SHA) that separate the external (source) and internal (induced) parts of the surface field. The conductivity profile determined from such an analysis can be sensitive to special characteristics of the quiet field itself as well as the separation techniques employed. This review of the Sq-analysis features critical to a conductivity derivation is pictorially presented along with the equations for application of theSchmucker (1970) technique to theSHA coefficients for a conductivity determination. Three examples illustrate the use of these equations with differentSq models.
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