Environmental Engineering Reference
In-Depth Information
Remnant
Source/sink
Metapopulation
(a)
REM
SS
META
(b)
REM
Space
high-quality habitat
low-quality habitat
population space-time trajectory
SS
META
Fig. 6.1
A space-time diagram illustrating the
principal difference between three types of regional
dynamics in plants: remnant, source/sink and
metapopulation dynamics. After Eriksson (1996).
Reproduced by permission of Oikos.
(c)
REM
and 6.2). The literature reveals evidence, indeed, for
the existence of all three kinds of regional-scale
dynamics in plants. For example, Van der Meijden
et al.
(1992) distinguished between three types of
biennial plant species that form metapopulations:
transient species and fugitive species, which are both
types of classical, typical metapopulation, and persist-
ent species, with metapopulations within sites. Long-
lived seed banks of the species that do not occur in
the established vegetation represent remnant popula-
tions. Freckleton and Watkinson (2002) proposed a
rearrangement of the terminology when dealing with
regional plant population dynamics, which I tend to
adopt here, namely:
SS
META
Space
Fig. 6.2
Hypothetical relationships between capabilities
of plants to disperse in space and persist (disperse in
time), in relation to three types of expected regional
dynamics: remnant (REM), source/sink (SS) and
metapopulation (META) dynamics. A general trade-
off between temporal vs spatial dispersal is assumed.
(a) Regional dynamics related to plant features;
(b) range contraction and expansion may alter
regional dynamics; (c) rate of dynamics may alter
regional dynamics. After Eriksson (1996). Reproduced
by permission of Oikos.
•
metapopulations
sensu stricto
: classic metapopula-
tions of mainland-island systems with predominantly
source/sink populations;
•
regional assemblages
: local processes dominate
and the constituent populations may be basically
unconnected;
•
spatially extended populations
: a spatially
extended form of the local populations, with con-
tinuous rather than patchy habitat.
In his classic study of the migration of terrestrial arth-
ropods, den Boer (1968) introduced the concept of
'spreading of risk', which implies that an investment
in dispersal can reduce the risk of extinction of a
population as a whole, even if local subpopulations
become extinct, provided that suitable sites are
within travelling distance. Den Boer (1990) placed 25
carabid beetle species into one of two groups: L-species
such as
Calathus melanocephalus
, occurring in stable
