Biology Reference
In-Depth Information
3000
W
I
I
W
W
W
R
W
I
W
2000
20% C
W
W
I
R
W
I
W
I
I
W
I
I
I
I
I
W
I
W
R
20% I
R
40% R
R
1000
10% W
R
R
R
R
R
R
R
0
R
CCCCCCCCCCCC
C
0
2
4
6
8
10
12
14
GENERATION
Fig. 17.7
Unique alleles retained in the right preserve only through 12 generations. Populations
C and I have short-distance dispersal of pollen and offspring (indicated by the small arrows
above diagrams depicting trial conditions to the right of the graph), while populations R and
W had long-distance dispersal (long arrows). Populations C and R had all 172 founders placed
in the left preserve only, while founders were split into two groups, one in each preserve, in
trials I and W. Numbers to right of diagrams indicate the height of the corridor as a percentage
of the length of one side of the preserve.
Thus, there appear to be no “position effects”, with founders closer to the
corridor entrance passing on their unique alleles exclusively. In trial W, there
is an initial decline in unique alleles in the right preserve, followed by an
increase due to the arrival of new alleles brought by offspring immigrants
from the left preserve under long-distance dispersal conditions. However,
in trial I, although founders are also split between the two preserves as in
trial W, dispersal is relatively short. Thus, after 12 generations, although
the right preserve population is growing (
Fig. 17.6A)
,
no new unique alleles
have arrived yet from the left preserve and alleles continue to be lost from
the right side founder population. These results, along with population
growth data, suggest that even though in some cases populations grow more
rapidly, in some cases more unique alleles are retained when founders are
placed on just one side of the preserve (e.g., populations V versus W in
Fig.
17.4);
splitting the founders with one group in each preserve provides some
protection for unique allele retention in case a large proportion of founders
or their immediate offspring are lost because of localized traumatic factors
that occur in only one preserve (e.g., fi re, pathogens). For example, although
populations I and C (
Fig. 17.1)
have similar rates of growth, C, initiated
with founders in only the left preserve, has no unique alleles in the right
preserve (Fig. 17.7), while I, with founders split between preserves, has a
signifi cant sampling of the unique alleles available in the source population.
Such considerations will contribute to optimization of restoration program
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