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density-dependent factorsdichteabhängige Faktoren (ger.)

  • An ecological factor (e.g., food) that becomes increasingly important in limiting population growth as the population size increases. (Oxford Dictionary of Genetics 2007)
    Howard and Fiske […] long ago pointed out that the natural causes of mortality in insects are separable into two categories, one of which, destroying a constant percentage regardless of the abundance of the insect, they called “catastrophic,” and the other, destroying a percentage which increased when the number of the host increased, they called “facultative.” […] Since the effect of of the one type is independent of density and that of the other is dependent upon density, it seems best to designate them as density-independent and density-dependent morality factors. […] Of the density-dependent factors, it is believed that entomophagous insects would have to be ranked at the head of the list in general, although in certain specific cases infectious and contagious diseases would precede them. The quantity of food also operates as a density-dependent factor
    Smith, H.S. (1935). The rôle of biotic factors in the determination of population densities. J. Econ. Entomol. 28, 873-898: 889-90.
    a perfectly density dependent factor will control increase of numbers endlessly […;] there is only one such factor for any species. That factor, the ultimate controlling factor […], is the competition between its own individuals. […] If it is evoked at all, no matter how seldom, then, in the long view, it is the all-important factor in preventing extinction from multiplication to the point of collective suicide
    Milne, A. (1957). Theories of natural control of insect populations. Cold Spring Harbor Symp. Quant. Biol. 22, 253-271: 264: cf. Nicholson, A.J. (1957). [Discussion statement]. Cold Spring Harbor Symp. Quant. Biol. 22, 216.
    There is only one perfectly density-dependent factor, intraspecific competition
    Milne, A. (1958). Perfect and imperfect density dependence in population dynamics. Nature 182, 1251-1252: 1251.
    Fragt man nach den Ursachen, die zu der Erhaltung des Artengleichgewichtes der ganzen Biozönose führen, so ergibt sich, daß diese Ursachen im wesentlichen außerhalb der einzelnen Art liegen, daß vielmehr diese von der Biozönose reguliert wird. In der Forstentomologie hat man eine Reihe dafür verantwortlicher Regulationsprinzipien und Regulationsfaktoren aufgedeckt und als dichteabhängige Faktoren bezeichnet.
    Hennig, R. (1959). Über eine „biozönotische” Minimum-Maximum-Regel“. Forschungen und Fortschritte 33, 131-132: 131.
    Es gibt nachweislich dichteabhängige Faktoren, das sind entweder positive, deren Wirkung mit zunehmender Dichte geringer wird (z.B. Gelegegröße) oder negative, deren Wirkung mit zunehmender Dichte stärker wird (Jungensterblichkeit, Parasitierung).
    Meunier, K. (1959). Grundsätzliches zur Populationsdynamik der Vögel. Zeitschrift für wissenschaftliche Zoologie 163, 397-445: 417.

    density dependent factor Density dependence q. v. 

    Lincoln, R.J., Boxshall, G.A. & Clark, P.F. (1982). A Dictionary of Ecology, Evolution and Systematics: 65.

    no population can be driven entirely by density-independent factors all the time. No matter how severely or unpredictable birth, death, and migration rates may be fluctuating around their long-term averages, if there were no density-dependent effects the population would, in the long run, either increase or decrease without bound
    May, R.M. & Seger, J. (1986). Ideas in ecology. Amer. Sci. 74, 256-267: 261.