Title:
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Effects of dispersal patterns on population dynamics and synchrony
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Authors:
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Janica Ylikarjula | Systems Analysis Laboratory Helsinki University of Technology P.O. Box 1100, 02015 HUT, FINLAND janica.ylikarjula@hut.fi www.sal.hut.fi/Personnel/Homepages/JanicaY.html
Susanna Alaja
Jouni Laakso
David Tesar
Date:
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April 2000
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Status:
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Systems Analysis Laboratory Research Reports E7 April 2000
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Abstract:
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In this paper we examine the effects of different dispersal patterns on the
dynamics of two and a larger number of coupled populations and on the level of
synchrony in local population dynamics. In these systems local population
renewal is governed by the Ricker model, which is characterized by a single
parameter, the intrinsic rate of increase r. Dispersal is assumed to be global
and dispersal rules explored here include a pattern where a constant fraction of
every local population disperses in each generation. In addition, we study the
effects of another density-independent and three density-dependent dispersal
rules. We also consider asymmetrical dispersal and the presence of
environmental heterogeneity. According to our results, the effects of density-independent
and density-dependent dispersal rules do not show any consistent
difference. However, we found that both population dynamics and the level of
synchrony differ markedly between two and a larger number of local
populations. For two patches different dispersal rules give very versatile results,
whereas for a larger number of local populations the dispersal patterns produce
qualitatively similar dynamics. For example, for the values of r yielding stable
or periodic dynamics in a single population, the dynamics do not change when
the patches are coupled with dispersal. In addition, for the values of parameter
r producing chaotic dynamics in a single population, dispersal has a stabilizing
effect on the dynamics. Increasing r may destabilize the dynamics, but
increasing the asymmetry of dispersal or assuming environmental heterogeneity
again stabilizes the dynamics. High intensity of dispersal does not guarantee
synchrony in fluctuations of local populations. The level of synchrony depends
also on dispersal rule, the number of local populations and intrinsic growth
rate.
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Keywords:
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theoretical biology, spatial models, bifurcation theory, density-independent and
density-dependent dispersal, environmental heterogeneity
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