Biology Reference
In-Depth Information
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A
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B
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GENERATION
GENERATION
Fig. 15.2
Observed heterozygosity across generations for trials modeling establishment of
the dioecious shrub
Lindera benzoin
. 172 founders were placed either in squares of 43 at each
corner with no founder closer than 80 grid units from a border (A, lowercase letters), or in
a single central square in the preserve (B, uppercase letters). In every trial, there were 4 grid
points between all adjacent founders. The different trials are compared to basic trials M or m,
in which 25% of offspring are dispersed to, and 25% of pollen comes from, each of the four
dispersal distance frames (see
Table 15.1)
.
Comparative trials differ as follows:
In trials N and n, more offspring are dispersed more closely to the maternal plant; 25% pollen
from each frame.
In trials O and o, 25% of an individual's offspring are dispersed to each frame; more pollen
comes from nearer the maternal plant.
In trials P and p, 25% of an individual's offspring are dispersed to each frame; more pollen
comes from a greater distance from the maternal plant.
For complete details on the trials, see text and Table 15.1.
most extreme cases of these trials (P versus o). Heterozygosity appears to be
affected much more by differences in pollen dispersal than by modifi cation
of offspring dispersal as modeled here.
Values of F likewise refl ect differences in genetic diversity for the
different trials (
Fig. 15.3)
.
For both graphs A and B, F values initially decrease
as the population declines slightly due to mortality before reproduction
begins in earnest (see
Fig. 15.1)
.
Then, F consistently increases more when
the 172 founders are broken into four groups, one at each corner (graph
A), than when the founders are in a central square (graph B). This effect is
due to increased inbreeding (see discussion of
Fig. 15.2)
combined with an
increased Wahlund effect induced by breaking the central population into
a set of more separated populations, and then analyzing them as though
they are one population (trials in A).
Relative to M and m, again, dispersing more offspring near maternal
plants while holding pollen at 25% to each dispersal frame has little effect
(N and n). However, with more pollen coming from nearer to the maternal
plant (O and o), F increases, while increasing more distant pollen dispersal
(P and p) reduces F.
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