Biology Reference
In-Depth Information
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GENERATION
Fig. 17.12
Trials comparing population growth under different conditions for a dioecious
perennial. All trials have identical input conditions except that trials 1 and 3 have all 172
founders placed in only one preserve while trials 2 and 4 have the founders split into two
groups of 86 each, one group placed in either preserve (which are separated by a corridor).
Trials 1 and 2 have corridors that are 20% the height of one preserve side, while trials 3 and
4 have corridors that are 40% that height.
increases population growth by approximately 21%. By comparison, in the
last section on annuals, population growth could be greater when founders
were split between preserves (
Fig. 17.11A;
O versus N), or when founders
were placed in one preserve only (
Fig. 17.8A
;
V versus W), depending on
input conditions. By the conventions made in the founder input statements,
all founders are aged 13, and thus by the age-specifi c reproductive schedule
(also input above), the founders will reproduce immediately. However,
their offspring must age according to that schedule until they become
reproductive. Note that population growth is not a simple curve, but rather
the curves increase more steeply in their latter generations. This refl ects
the increased reproduction provided by new cohorts as they come into
reproductive age.
At the termination of all of these trials, the mean of the unique alleles
retained is approximately 2,904 (out of an initial 2,905 to 2,909 possible among
these trials) with observed heterozygosity of 0.984, there being no larger than
a 1% difference among any of the trials for both variables (no signifi cantly
different values; all of these data not shown). Under these conditions, with
almost all founders remaining in the stands, and the relatively rapid expansion
of the total populations, major losses of unique alleles or heterozygosity do
not occur in these populations. Thus it would seem that, comparing these
cases, the reason to split the founders to two preserves would be to promote
population growth and to spread risk (bet hedging).
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