Chapter 13 Part 3 Flashcards
what are metapopulations composed of
subpopulations that can experience independent population dynamics across space
Preferred habitat often occurs as
patches of suitable habitat surrounded by a matrix of unsuitable habitat
Habitat fragmentation
the process of breaking up large habitats into a number of smaller habitats
habitat fragmentation often occurs as the result of
human activities (e.g., clearing forests, road construction, draining wetlands)
some habitat fragments experience extinctions, whereas others are
colonized by dispersers
The basic (first) metapopulation model assumes that
all habitat patches are equal in quality and that the matrix between patches is inhospitable.
Sources
high-quality patches that produce a large number of individuals that disperse to other patches
Sinks
low-quality patches that produce few individuals and rely on dispersers to keep the sink population from going extinct
If subpopulations rarely exchange individuals, fluctuations in abundance will be
independent among subpopulations
If subpopulations frequently exchange individuals, the subpopulations will
act as one large population
With intermediate patch connectivity, abundance in one subpopulation can influence
the abundance of other subpopulations
Assume that habitat patches are
of equal quality, each occupied patch has the same subpopulation size, and each subpopulation supplies the same number of dispersers to other patches
The proportion of occupied patches when colonization and extinction have reached an equilibrium (𝑝̂) is represented as:
𝑝̂ = 1 - (e/c)
We can increase the number of occupied habitat patches by
providing corridors between patches to increase the rate of colonization (c)
p
the fraction of habitat patches that is occupied
e
the probability of each patch becoming unoccupied (i.e., going extinct)
c
the probability of a patch becoming colonized
We can also increase the number of occupied patches by decreasing
rates of extinction (e)
Hence, species may be preserved by protecting
large fragments of habitat that reduce extinction risk, or by ensuring that individuals can disperse to and from patches.
Habitat patches are rarely equal in quality;
some patches are larger or contain a higher density of resources
Small patches are likely to experience
higher rates of extinction and are less likely to be occupied than large patches
Dispersal success is inversely related to
the distance of dispersal; hence, more distant patches will have a lower probability of being occupied than closer patches.
Unoccupied patches that are close to occupied patches are more likely to be
colonized
Rescue effect
when dispersers supplement a declining subpopulation and thereby prevent it from going extinct
Less isolated patches are more likely to be
rescued and are also more likely to be colonized
After settlement of farmers in western United States, habitat loss substantially reduced the number of
black-footed ferrets
what reduced numbers even more
poisons and disease
In 1981, a small population in Wyoming was discovered and a captive breeding program was very successful
Using metapopulation theory, biologists conducted several reintroductions in locations throughout western North America. This created a metapopulation that was resistant to complete extinction
