Biology Reference
In-Depth Information
the “short-distance” regimen described earlier for the trials with annuals
with a maximum dispersal distance of 701 units. As before, long-distance
dispersal refers to increasing each dispersal category by a factor of four,
the maximum dispersal distance being 2,804 units. In the trials compared
in Fig. 17.14, all the conditions were the same as described above for trials
3 and 4 with corridor height equal to 40% the length of one preserve side,
with the following exception: trials 3 and 4 had short-distance dispersal
while trials 5 and 6 had long-distance dispersal. Trial 5 was like trial 3 in
that all 172 founders were placed in a single square in one preserve, while
in trials 4 and 6, the founders were split into two smaller groups, one in
each preserve.
Figure 17.14 demonstrates that whether dispersal is short or long,
populations grow faster when the founders are divided between the two
preserves: trial 4 is greater than 3, 6 greater than 5 (by 13.6% in the latter
case at generation 17). At generation 12, trial 5 is 49% greater than trial 3,
and 6 is 31% greater than 4, and thus, long-distance dispersal increases
population growth substantially when founders are in one group or split
into two groups. Little or no difference was found among any of these trials
as to the level of observed heterozygosity (0.98 to 0.99) or amount of unique
alleles retained (approximately 2,905 unique alleles, this being a drop of
one allele from the number retained in the founders).
70000
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GENERATION
Fig. 17.14
Trials comparing population growth under different conditions for a dioecious
perennial. All trials have identical input conditions except that trials 3 and 4 have short-distance
offspring and pollen dispersal (maximum dispersal = 701 units) while trials 5 and 6 have long-
distance dispersal (maximum = 2,804 units with all short-distance categories extended by a
factor of four). Trials 3 and 5 have the 172 founders placed in one square in one preserve, while
trials 4 and 6 have the founders split into two smaller groups, one in each preserve.
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