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4.1.1 Demographic significance Confined populations grow more
rapidly than populations from which dispersal is permitted
(Lidicker, 1975; Krebs, 1979; Tamarin et at., 1984), and demography
in island populations where dispersal is restricted differs greatly
from nearby mainland populations (Lidicker, 1973; Tamarin, 1977,
1978; Gliwicz, 1980), clearly demonstrating the demographic signi
ficance of dispersal. The prevalence of dispersal in rapidly
expanding populations is held to be the best evidence for
presaturation dispersal. Because dispersal reduces the growth rate
of source populations, it is generally believed that emigration is
not balanced by immigration, and that mortality of emigrants occurs
as a result of movement into a 'sink' of unfavourable habitat. If
such dispersal is age- or sex-biased, the demo graphy of the
population is markedly affected, as a consequence of differ ences
in mortality in the dispersive sex or age class. Habitat
heterogeneity consequently underlies this interpretation of
dispersal and its demographic consequences, although the spatial
variability of environments is rarely assessed in dispersal
studies."
4.1.1 Demographic significance Confined populations grow more
rapidly than populations from which dispersal is permitted
(Lidicker, 1975; Krebs, 1979; Tamarin et at., 1984), and demography
in island populations where dispersal is restricted differs greatly
from nearby mainland populations (Lidicker, 1973; Tamarin, 1977,
1978; Gliwicz, 1980), clearly demonstrating the demographic signi
ficance of dispersal. The prevalence of dispersal in rapidly
expanding populations is held to be the best evidence for
presaturation dispersal. Because dispersal reduces the growth rate
of source populations, it is generally believed that emigration is
not balanced by immigration, and that mortality of emigrants occurs
as a result of movement into a 'sink' of unfavourable habitat. If
such dispersal is age- or sex-biased, the demo graphy of the
population is markedly affected, as a consequence of differ ences
in mortality in the dispersive sex or age class. Habitat
heterogeneity consequently underlies this interpretation of
dispersal and its demographic consequences, although the spatial
variability of environments is rarely assessed in dispersal
studies."
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