Biology Reference
In-Depth Information
The populations with the most subdivided founders, a and b, have the
greatest declines in observed heterozygosity, the latter having the greatest
decline. No signifi cant differences in observed heterozygosity were found
for trials c versus d or e versus f, although these pairs of trials differ from
each other, with more limited dispersal reducing the loss of heterozygosity.
This reduction appears to result from the slower population growth of trials
e and f (compare H values for trial c at generation 82 with trials e and f
at generation 100 when populations are of approximate equal size). The
greatest heterozygosity difference between any of these trials (b versus f)
is only about 2.5%, so subsequent effects of increased inbreeding stemming
from founder placement are not likely to be a major issue at generation
100. Note, however, that the trajectories for these trials differ, and values
of observed heterozygosity will differ increasingly through further bouts
of reproduction, at least in the near future.
The trajectories of F value also differ among some of these trials
(
Fig. 16.5A).
Trials e and f (lowest curve) have the least deviation in
observed heterozygosity values from expected and it appears that they will
plateau somewhere between 0.01 and 0.02 in the near term. Shorter average
offspring dispersal distance from the carpellate parent with an extended tail
of pollen distribution distance appears to reduce inbreeding-subdivision
when founders are placed in one square (compare trials e and f versus c
and d; also, recall the effects of smaller population size on heterozygosity
noted in the previous paragraph). Although dividing an equal number of
founders into separated squares leads to increased values of F (trials a and
b), insetting the founders by a greater distance has the greatest effect on
increasing the F value (trial b). Although, at least in the near term, trials c,
d, e and f have F values well below 0.05, trials a and especially b appear
to be have rates of change such that trial b, at least, will likely rise above
moderate localized inbreeding (trial b loses observed heterozygosity at the
most rapid rate in
Fig. 16.4B)
and subpopulation differentiation levels of
0.05 in coming generations.
As for unique alleles retained by these different populations (Fig. 16.5B),
the greatest difference between trials (trials c versus a) amounts to less than
1%. So if unique allele loss is the major consideration in a restoration project,
any of these patterns of introduction produce similar results regardless of
the life history comparisons made here. Given all of the above, it would
seem that the conditions for trial d would provide the greatest returns
(primarily in terms of population growth) per unit effort of introduction.
However, if the risk of localized fi re, pathogens, and other adverse factors
is to be spread, then conditions for trial b would be preferred.
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