Biology Reference
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degree of subdivision, with different groups placed at suffi cient distance
from different borders, to prevent population or genetic edge effects may
allow for less costly restoration or conservation projects.
NEWGARDEN can be used to investigate the effects of varying
degrees/rates of admixture of separated subpopulations on population
growth and genetic diversity.
Gene dispersal as indicated by measured offspring propagule and
pollen distances is not the entire story for realized gene dispersal. Measured
offspring and pollen dispersal interacts with spationumerical patterns
of establishment, edge effects, life history characteristics, population
subdivision, and rates of population growth, all of which in turn affect
realized gene dispersal. NEWGARDEN analyses can be used to explore the
population and genetic effects stemming from asymmetries in gene fl ow
brought about by differing distances of pollen versus offspring dispersal.
Although some theory indicates that even low rates of intermigration
(e.g., one individual exchanged per generation in ideal populations;
Allendorf 1983: 55) prevent genetic differentiation between subpopulations,
some NEWGARDEN analyses showed that, even with appreciable
exchange of offspring and pollen, unique alleles can still disappear from
one subpopulation or the other or both through time. When founders are
placed in subpopulations rather than in one initial group, F values are
elevated. Such subpopulations are often not genetically homogenized over
several generations despite signifi cant gene exchange in such examples.
This lack of homogenization would seem to increase with an increasing
number of unique alleles, all at lower frequencies, at loci. These fi ndings
support the conclusions of Rauch and Bar-Yam (2004), who found that it
is to be expected that genetic diversity is not apportioned evenly across
subpopulations even when gene fl ow regularly occurs.
Differing percentages of the dispersal of offspring or microgametes
to different dispersal distance zones can have a pronounced effect on
population growth and population genetic diversity.
When some populations grow faster because of longer-distance
dispersal under a specifi c set of heritable life history conditions, longer-
distance dispersal may be selected for, since offspring survival (fi tness)
is increased when dispersal is more widespread. However, such longer-
distance dispersal can also lead to increased loss of heterozygosity,
inbreeding, and/or loss of unique alleles.
NEWGARDEN trials above show that dioecious species may differ
from otherwise similar bisexual species in the effect of other life history
attributes on population growth, population genetic diversity, and their
management.
NEWGARDEN trials were used to examine changes in the population
growth and genetics of individual successive cohorts with changes to
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