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were exactly the same as in trials M and m described above except for the
following: both trials begin with only 43 founders in one group; in trial
v, the 43 founders are placed at one corner (at the same distance from the
border as used for each group of 43 founders in trial m); in trial W, the 43
founders are placed at the center of the preserve (similar to trial M). Thus,
in trials v and W, we have removed the effects of subdivided founders and
are directly examining the effects of smaller groups of founders placed both
near preserve borders (trial v) and far from them (trial W).
In Fig. 15.9A, mean population growth for the M basic trial (172
founders in one central square) and m trial (172 founders divided to four
squares, one in each corner) demonstrate that population growth is slower
in the latter. Likewise, when only one square of 43 founders is used, the
population grows more slowly if founders are placed in a corner near a
border (trial v) than when the founders are placed centrally (trial W). This
confi rms that more individuals are dispersed outside the preserve, leading
to slower population growth, when founders are placed near preserve
corner borders.
Mean F values for these trials are given in Fig. 15.10A. All populations
rapidly drop below 0 at fi rst because of an excess of observed heterozygotes.
Note that all trials begin with higher levels of observed than expected
heterozgosity, most likely due to the fact that, because of limited sampling
of the source population, and death of individuals before reproduction
commences, heterozygotes are more frequent than would be expected
from allelic frequencies (a deviation from Hardy-Weinberg equilibrium).
Comparison of graph A with graph B of Fig. 15.9 reveals that, as
expected, F remains negative until the lines for expected versus observed
heterozygosity cross and the expected values thereafter are increasingly
greater than the observed values in F, yielding an increasing F. Since there
is a greater difference between expected and observed heterozygosity in
later generations for trial m (Fig. 15.9B), this population has the most rapid
rise in F in later generations.
To examine which of the factors numbered above infl uence greater F
values when founders are subdivided to the corners, we will also refer to
output data depicted for trials m, M, v, and W in Fig. 15.9B (heterozygosity
values) and Fig. 15.10 (mean F values and unique alleles retained). The
potential contribution of these factors to the greater F values generated
when founders are subdivided into groups at corners will be reviewed in
the order outlined just above.
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