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  • 1
    Book
    Book
    Cambridge [u.a.] : Cambridge Univ. Press
    Keywords: Ökologie ; Experiment ; Ökologie ; Methode
    Type of Medium: Book
    Pages: XIII, 370 S. , graph. Darst.
    ISBN: 0521345960 , 0521346924
    Series Statement: Cambridge studies in ecology
    DDC: 574.5'0723
    RVK:
    Language: English
    Note: Hier auch später erschienene, unveränderte Nachdrucke
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 439.2006, 7072, E1-, (2 S.) 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Arising from: W. A. Nelson, E. McCauley & F. J. Wrona Nature 433, 413–417 (2005); Nelson et al. reply. A variety of mechanisms can theoretically produce competitive coexistence in nature, making it hard to identify a ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 405 (2000), S. 1047-1049 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Food-chain length is an important characteristic of ecological communities: it influences community structure, ecosystem functions and contaminant concentrations in top predators. Since Elton first noted that food-chain length was variable among natural systems, ecologists have considered ...
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Natural selection can lead to rapid changes in organisms, which can in turn influence ecosystem processes. A key factor in the functioning of lake ecosystems is the rate at which primary producers are eaten, and major consumers, such as the zooplankton Daphnia, can be subject to strong ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Ecological and evolutionary dynamics can occur on similar timescales. However, theoretical predictions of how rapid evolution can affect ecological dynamics are inconclusive and often depend on untested model assumptions. Here we report that rapid prey evolution in response to oscillating ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 54 (1992), S. 313-334 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Studies of plant and animal populations have demonstrated the occurrence of multiple and mixed life history strategies such as polymodal timing of germination and emergence from dormancy. We present the results of a simulation model used to test whether between-year variance in mortality can lead to the persistence of multiple hatching strategies considered over an ecological time scale (50 years). The model is based on the general life history characteristics of a population of planktonic copepods (Diaptomus sanguineus) in Bullhead Pond, Rhode Island. Our model results demonstrate that, given a range of between-year variance in mortality, multiple strategies for timing of emergence can persist in a common environment for ecologically relevant periods of time. A qualitative test of the model comparing field estimates of mean and variance of mortality in Bullhead Pond with the region of persistence indicates that the model results are in approximate agreement with field estimates. The results suggest that variability in year-to-year selection pressures, such as predation or harsh winters, may play an important role in determining the evolution of life histories.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Populations of the planktonic copepod, Diaptomus sanguineus, live in permanent and temporary freshwater ponds in Rhode Island. All ponds in which they occur become uninhabitable at some time during the year, but the nature and timing of the harsh period varies both spatially and temporally. Females produce discrete clutches either of subitaneous eggs which hatch immediately or of diapausing eggs which hatch the following season. The two egg types show distinct chorion morphologies under transmission electron microscopy. In permanent ponds the copepods start making diapausing eggs in March, one month before rising water temperatures induce planktivorous sunfish to become active. In temporary ponds diapausing eggs are produced, in a complex pattern from May to July, before the water disappears in late summer or early fall. We investigated the spatial scale at which D. sanguineus is adapted to this complex environment. In a reciprocal transfer experiment between temporary and permanent bodies of water, female copepods placed in new ponds made subies of water, female copepods placed in new ponds made subitaneous and diapausing eggs in the same sequence as control females retained in their home ponds. The copepod populations enter diapause at times appropriate for the local habitat conditions they experience, but inappropriate for other, nearby ponds. Transplanted females were unable to sense a change in pond type or to adjust egg production accordingly. We conclude that D. sanguineus populations are adapted to the specific conditions of isolated ponds rather than to a broader geographical region containing several pond types.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5125
    Keywords: aquatic invertebrate herbivore ; biological control ; Finger Lakes ; freshwater herbivory ; Euhrychiopsis lecontei ; survey ; screening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Myriophyllum spicatum, an exotic submersed macrophyte causing serious lake management problems throughout much of North America, decreased markedly in biomass in Cayuga Lake, NY, USA, since the beginning of the 1990s. Over the same period, however, the total biomass of all species of submersed macrophytes did not decline, and native macrophytes gained in abundance. The aquatic moth larva, Acentria ephemerella, was first observed on milfoil plants in Cayuga Lake in 1991. However, due to its cryptic habit the larva may have been present prior to that year. When the density of these grazers is high, herbivory by Acentria causes severe damage to the apical meristem of M. spicatum. This moth larva and another milfoil herbivore, Euhrychiopsis lecontei are widespread in 26 lakes surveyed in New York State; they are present in 25 and 24 lakes, respectively. Estimates of Acentria larval densities in summer in Cayuga Lake are 27 to 100 m-2, and a quantitative survey of larvae hibernating in milfoil stems revealed mean densities of 500 m-2 in late fall in Seneca Lake. In laboratory experiments, Acentria larvae feed on a wide variety of macrophytes commonly found in New York State. Although Acentria is not a specialist feeder, its life cycle is closely tied to M. spicatum through the moth's use of apical tips and stems for summer and winter refuges; thus deleterious damage to other macrophytes is low.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-8477
    Keywords: Aggression ; altitudinal distribution ; food interference ; North Carolina ; Plethodon ; salamander
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary One of the central assumptions of evolutionary ecology is that interspecific competition is a potent evolutionary force acting on coexisting species. There are few animal species that provide an opportunity for an experimental analysis of the evolutionary consequences of the phenomenon. We have taken advantage of the fact that two species of terrestrial salamander,Plethodon glutinosus andP. jordani, have different altitudinal distributions on two mountain ranges in North Carolina. Field removal experiments showed that interspecfic competition was much stronger in the Great Smoky Mountains than in the Balsam Mountains, and transplant experiments between the two mountain ranges showed that neither species from the Balsam Mountains had a measurable effect on its congener in the Smokies, although both species from the Smokies had strong negative effects on the Balsam congeners. Other experiments were conducted on the behavioral and ecological changes that have (or have not) evolved in the two areas. Our studies show that increased interspecific interference was the major evolutionary response of these largePlethodon species to interspecific competition, and that partitioning of food or microhabitat was not involved.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 332 (1996), S. 63-70 
    ISSN: 1573-5117
    Keywords: bioturbation ; sediment dynamics ; diapausing eggs ; Diaptomus sanguineus ; Tubificidae ; Chironomidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ecological and evolutionary dynamics of zooplankton is in part a function of the numbers and ages of dispausing eggs hatching from aquatic sediments. Successful recruitment from this ‘egg bank’ must depend upon the eggs being present at or near the sediment surface. Often, however, zooplankton diapausing eggs are found as deep as 15 to 30 cm in the mud. Bioturbation may provide a mechanism for the regular return of buried eggs to the sediment surface. A substantial portion of the population of the copepod, Diaptomus sanguineus, living in Bullhead Pond, a small lake in Rhode Island, USA, is present as diapausing eggs. To study the role of bioturbation in egg-bank dynamics, we introduced polystyrene beads, the same size and specific gravity as copepod eggs, at two depths in large-diameter sediment chambers in the laboratory. Treatments included chambers with natural and reduced densities of benthos. Consistent with other studies, our results show that the joint activities of tubificid oligochaetes and chironomid larvae are responsible for bidirectional (up and down) transport of beads in the top 2 cm of the sediment. We observed no bead movement below this depth. Thus, eggs in the top two centimeters of sediment in this lake are exposed with some regularity to conditions that stimulate hatching at the sediment-water interface. In Bullhead Pond, these eggs have a mean age of 12.2 years (based on 210Pb-dating). Eggs buried more deeply will only be returned to the sediment surface by relatively rare, localized disturbances. This return of old eggs to the surface affects ecological and evolutionary dynamics in a complex way.
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