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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 68 (1986), S. 595-600 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Field observations and laboratory experiments were carried out to determine the influence of body length of preys on the acceptance rate by spiders. Feeding experiments with 13 spider species and a model prey (crickets) reveal a decreasing acceptance rate with increasing prey size. Prey sizes of 50–80% of the spiders' size yielded the highest acceptance rates, crickets of double the spiders' size were accepted by two species only. By fitting the acceptance rate Y versus prey size X by Y(x)=Y(0) (1-βx2), two coefficients could be calculated: Y(0), the size-independent palatibility of the prey and β, a coefficient of size-induced refusal of the prey. These values describe the degree of specialisation towards (a) crickets and (b) large prey, respectively. Further comparison showed (a) that labidognath (= araneomorph) spiders do not necessarily subdue larger prey items than orthognath (=mygalmorph) spiders and (b) that webbuilding spiders are superior to non-webbuilding spiders in respect of catching large prey. A modified model of the generalized pattern of the length relations of predator and prey is given with special reference to spiders and compared to other polyphagous predator groups.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: Key words Terminology ; (Ecological) stability ; Resilience ; Persistence ; Generality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We present an inventory and analysis of discussions of ecological stability, considering 163 definitions of 70 different stability concepts. Our aim is to derive a strategy that can help to dispel the existing ”confusion of tongues” on the subject of ”stability” and prevent its future recurrence. The strategy consists of three questions that should be kept in mind when communicating about stability properties. These three questions should overcome the three main sources of confusion in terminology. Firstly, which stability properties are being addressed in the stability statement? Our analysis shows that the general term ”stability” is so ambiguous as to be useless.It can be replaced by the stability properties ”staying essentially unchanged” (constancy), ”returning to the reference state (or dynamic) after a temporary disturbance” (resilience), and ”persistence through time of an ecological system” (persistence). Second, to what ecological situation does the statement refer? An ecological situation is defined by a set of features that, taken as a whole, determine the domain of validity of a stability statement. The six most important features form the ”ecological checklist”, which serves to classify ecological situations and thereby provides a system of coordinates for communication. The six points are: variable of interest, level of description, reference state, disturbance, spatial scale and temporal scale. Thirdly, is the statement anchored in the situation in question, or is there unacceptable generalisation by inferring ”stability” of the whole system from a certain stability property in a certain ecological ecological situation? This question separates the scientifically valuable content of a statement from the desire for general statements which is often projected through stability statements.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Landscape ecology 13 (1998), S. 363-379 
    ISSN: 1572-9761
    Keywords: landscape indices ; long-term persistence ; metapopulation ; rules of thumb for landscape management ; spatial configuration ; species' ecology ; stochastic model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of spatial configuration for metapopulation survival is analyzed by using a stochastic metapopulation model. This model reveals conditions which must be satisfied by the species' ecology and the landscape settings before a metapopulation can persist over a long term. Taking this as a basis, initial rules of thumb for landscape management are deduced. The following results are highlighted: (1) the critical correlation length dc of the extinction processes determines a spatial scale of the metapopulation dynamics. (2) Only species with a dispersal range dr above the correlation length dc are able to benefit from landscape management at all. (3) A certain metapopulation can only persist over a long term if no patch is inside the range of correlation of another one. (4) There is a hierarchy of importance in the characteristics of a spatial configuration (scale and type) and, hence, in the scopes of landscape management. To conclude, some general consequences for supporting species survival by management are discussed. Some prospects concerning the use of models for decision support in landscape planning are discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 23 (1993), S. 295-300 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Die theoretische Ökologie ist eine vergleichsweise junge Wissenschaft, die in den angelsächsischen Länder schon wesentlich besser etabliert ist als im deutschsprachigen Raum. Mit Hilfe von Modellen versucht man, ein besseres Verständnis von ökologischen Prozessen und Zusammenhängen zu gewinnen.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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