Metapopulations
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A metapopulation has been defined as 'a population
consisting of spatially-separate subpopulations that are connected
by the dispersal of individuals' (Forman,
1995). Metapopulation dynamics exist where there are small isolated patches containing subpopulations, which can become locally extinct. Dynamics result from changes within local populations including periodic extinction coupled with intermittent colonisation from other locations. |
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The metapopulation can maintain in the landscape under these conditions because individuals move between subpopulations. So when local extinction occurs, recolonisation can re-establish a new subpopulation at that site.
At the local scale there is instability within these
isolated patches, but on the broad scale there is stability within the
metapopulation. Problems however, will arise if there is local extinction
within each sub population (Forman,
1995).
Factors such as density, degree of aggregation and connectivity
of suitable habitat will influence colonisation rates.
Size of remnant patches will influence the number of
dispersers and the risk of local extinctions.
Metapopulations will grade into source-sink populations
if local populations consistently sustain net positive growth rates, have
little risk of extinction and produce colonists to other localities with
net negative growth rates and or high risks of random extinction (Forman,
1995).
Landscape features such as habitat isolation and heterogeneity
influence spatial structuring of populations, and determine whether they
exhibit source-sink or metapopulation dynamics.
