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C00002 00002	biolog[f86,jmc]		Notes on biology
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biolog[f86,jmc]		Notes on biology

Population Biology, Thomas C. Emmel, Harper and Row 1976

Emmel describes various forms of natural selection that have
been observed.  However, the observations seem to be open to
the criticism that selection for one trait at one time of the
year might be counterbalanced by selection for another trait
at other times of the year or during episodic crises.
Temporal inhomogeneity might thus account for the persistence of
genetic variablity.

Temporal inhomogeneity is to be added to spatial inhomogeneity.

p. 120 Emmel doesn't seem to include territoriality in his
list of factors determining of carrying capacity.

p. 121 reference to Ehrlich and Birch (1967).  The "balance of nature"
and "population control". American Naturalist 101, 97-107.

p. 141
Andrewartha and Birch (1954) emphasize the importance of habitat
heterogeneity, whith spacial patchiness and fluctuations occurring
in physical components of the environment".
Andrewartha, H.G. 1961 Introduction to the Study of Animal Populations.
University of Chicago Press.

Milne (1957, 1958, 1961, 1962) emphasizes "protective niches where
prey can hide from its enemies".

p. 158
Does a niche include the availability of hiding places from  predators?
If so, then the niche depends on whether certain predators are present.
But one of the recognized variables such as humidity can function in
this role, in that certain plants can't stand too much humidity, because
their roots rot from some fungus.  But this means that the size of the
niche in the humidity dimension depends on whether the fungus is present.
Conjectures:

None of the population biology models I have seen take inhomogeneity
in space and time into account.  We concentrate on spatial inhomogeneity.
The environment is patchy, and some places are better for a given
species than others.  For example, predator-prey relationships vary from place
to place; some places have more hiding places for the prey.
The availability of food and shelter differs from place to place
as does humidity and temperature.

Therefore, we should expect that some parts of the range of a species
act as sources and others as sinks.  It is important to determine
in particular cases
whether the net flows are are just the difference between diffusion
in both directions or whether there is little or no upstream flow.
If the latter then effective population sizes relevant to genetic
drift are much smaller than would be estimated taking the entire
population into account.  If there are many sources in a region,
then each can act as an independent source of drift and variation.

Territoriality might tend to cause reduced upstream flow.  In a
good neighborhood territories that become available are quickly
taken by locals.  In a bad neighborhood territories open up all
the time because of the decease of the occupants.