By N. C. Stenseth, W. Z. Lidicker Jr (auth.), Nils Chr. Stenseth, William Z. Lidicker Jr (eds.)
4.1.1 Demographic value limited populations develop extra speedily than populations from which dispersal is authorized (Lidicker, 1975; Krebs, 1979; Tamarin et at., 1984), and demography in island populations the place dispersal is particular differs vastly from within sight mainland populations (Lidicker, 1973; Tamarin, 1977, 1978; Gliwicz, 1980), basically demonstrating the demographic signi ficance of dispersal. the superiority of dispersal in swiftly increasing populations is held to be the simplest facts for presaturation dispersal. simply because dispersal reduces the expansion fee of resource populations, it's usually believed that emigration isn't balanced by means of immigration, and that mortality of emigrants happens because of circulate right into a 'sink' of damaging habitat. If such dispersal is age- or sex-biased, the demo graphy of the inhabitants is markedly affected, on account of fluctuate ences in mortality within the dispersive intercourse or age classification. Habitat heterogeneity for this reason underlies this interpretation of dispersal and its demographic outcomes, even if the spatial variability of environments is never assessed in dispersal studies.
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Extra info for Animal Dispersal: Small mammals as a model
Is it genetically directed? What environmental circumstances induce it? What internal states motivate it? Criteria Fitness contribution Relation to carrying capacity or density Responsiveness? Heritabilities Environmental cues or behavioural stimuli Internal drive ing, travelling, and arriving. The new home range must be disjunct from the abandoned one, although it is possible that an individual may at some future time disperse back to the original home range. 1). 1). Nomads are deviants of the travelling phase of dispersal.
By truncation selection; Wills, 1978; Wallace, 1970, 1975), selection cannot act strongly (5 = 1) at more than a handful of loci without causing an unacceptably high variance in fitness. The simple Levene model can be strengthened slightly by supposing that individuals tend to return to the type of patch on which their mother was reared. 1a). The model may also be strengthened by allowing some spatial subdivision of the mating population (Karlin, 1982). Again, this is of little help: in general, although spatial subdivision can allow substantial variation between populations, it cannot maintain much variation within populations unless the scale of environmental heterogeneity is closely matched to the scale of spatial differentiation (Barton and Clark, 1990).
How such controls evolved remains an important question, though for sex biases in dispersal, it has been suggested that inbreeding avoidance is involved (Packer, 1979, 1985; Greenwood, 1980; Brandt, 1985; Chapter 5). Others feel that it has to do with mate competition between parents and their like-sexed offspring (Anderson, 1980, 1989; Dobson, 1982; Moore and Ali, 1984). Still another possibility is that the dispersive sex corresponds to the territorial sex (Chapter 9). The argument is that territorial spacing behaviour encourages dispersal in individuals of the territorial sex who lack territories.
Animal Dispersal: Small mammals as a model by N. C. Stenseth, W. Z. Lidicker Jr (auth.), Nils Chr. Stenseth, William Z. Lidicker Jr (eds.)