Hanski, I. 1982. Dynamics of regional distribution: The core and satellite species
hypothesis. Oikos 38:210-221.
The core-satellite species hypothesis
(sometimes referred to as CSS) states that
species fall on a continuum between two
categories:
Core species are locally abundant and
regionally common
Satellite species are locally rare and regionally
rare.
The CSS hypothesis grew out of the logistic growth equation (dN/dt= rn(1-N/k)), as
modified by Levins (1969, 1970) to produce a growth equation based on spatial
distribution (dp/dt=ip(i-p)-ep) where p is the proportion of sites a single species occurs in
and i and e are rates of site colonization and local extinction respectively. In deriving his
model, Hanski relied on the following definitions and assumptions:
1. Abundance refers to the number of individuals at a local population site (say a city
park)
2. Distribution refers to the number of sites occupied by the species (number of parks a
species occurs in)
3. Dynamics in local abundance and regional distribution are local interdependent… if
you study similar habitats in the region. The more locally abundant a species, the more
sites it will occur in as well (local abundance=high regional distribution).
4. Extinction in a local site is not a constant property of a species and instead depends on
p.
With colonization and immigration rates of a local site depending on the number of sites
already occupied (p), populations will tend towards one of the other of the deterministic
boundary equilibria: p= 0 or p=1. By contrast, Levin thought that the relationship (shown
in the graph below) should be unimodal: there is an equilibrium number of sites a species
should occupy.
Predictions that follow from the CSS hypothesis:
1. Species may be put on the CSS continuum and may change between classes between
landscapes or thru time.
2. Satellite species existence should hinge on the size of the region. As regions become
smaller, proportion of satellite species should decline.
3. Core species might reach MacArthur-Wilson equilibrium while satellite species won’t
4. Core species should be better spaced out in niche space than satellite species.
Ilkka Hanski: Finish (Finnish? Finlandish?) metapopulation biologist primarily
interested in insects jumping around between landscape fragments. Has some interesting
models on his website on patch occupancy and connectivity.
(http://www.helsinki.fi/~ihanski/)