Biology Reference
In-Depth Information
Figure 8.11 shows how F changes as the different populations initiated
with founders at different distances to the right from the left border
grow in number. For a given population size, F appears to increase with
founders placed at greater distances from the left border, suggesting that
small population size alone is not a major infl uence in these differences in
F (higher values of F found in smaller populations due to more changes
induced by inbreeding and/or drift in allele frequencies).
0.07
F
F
F
F
FF
T
F
F
T
T
T
T
T
T
T
F
2
F
F
2
22
2
2
2
2
2
F
TT
0.03
2
2
TT
F
F
TT
2
2
2
2
F
T
T
F
2
-0.01
T
F
2
F
T
2
2
T
F
2
2
F
-0.05
0
1000
2000
3000
MEAN POPULATION
Fig. 8.11
Change in mean F values (30 runs per trial) relative to mean population size for
the trials described for
Fig. 8.10.
Founders are horizontally shifted to increasing distances
from the left border of a preserve. Trial 2 = founders at lower left corner; trial T = founders
moved 10 grid units to the right; trial F = 50 units right. The fi nal point to the right in each
trial represents the mean F value at the end of the trial (after 21 generations). All of these last
mean values differ signifi cantly (p < 0.05).
Alleles Retained per Locus
So far, in examining the population genetic effects of placing founders at
different distances from a preserve border, we have examined only issues
surrounding population growth rate, heterozygosity, and F values. Another
measure of genetic diversity is the number of unique alleles residing in
a population. For example, one population may have a locus with four
unique alleles (each with a different frequency, the sum of the frequencies
being equal to 1), while another may have seven unique alleles for that
locus. From this point on, we will generally use the term “alleles” to refer
to unique alleles unless stated otherwise. Rather than being concerned with
the potential absolute number of alleles in establishing populations (this can
simply be calculated as two times the number of founders), we explore how
many unique alleles across loci are preserved as establishment proceeds.
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