Biology Reference
In-Depth Information
NEWGARDEN can be used to compare population growth and genetic
diversity retention relative to edge effects (e.g., distance of founders from an
edge) for populations differing with regard to preserve edge characteristics,
founder number and spatial placement, and life history characteristics.
Populations initiated from founders placed nearer borders can grow
at slower rates than those initiated from founders placed further into the
preserve.
Populations initiated with founders nearer borders can lose
heterozygosity (observed or expected) more slowly than those initiated
from founders placed further into the preserve.
Populations initiated with founders nearer borders can experience less
inbreeding (as indicated by F values) than those initiated with founders
placed further into the preserve.
Differences in the number and frequencies of unique alleles available per
locus have only slight effects on
rates
of change in levels of heterozygosity
relative to founder distance from borders. However, the absolute values
of heterozygosity differ between trials that are identical except for allelic
diversity per locus (Fig. 8.16).
Differences in the number and frequencies of unique alleles available
per locus can have a pronounced effect on unique alleles retained by
populations initiated with founders at different distances from preserve
borders. When unique alleles are numerous and at low frequency on a per
locus basis, loss of unique alleles can offer a sensitive measure of population
genetic effects driven by edge effects and differing initial conditions
among trial populations (e.g., founder placement geometry, life history
characteristics).
Moving founders from a border only slight distances (in terms of
average density for the species, as well as in terms of offspring or pollen
dispersal distances) can reduce losses of diversity to levels similar to when
founders are placed in the center of a preserve, at least under the conditions
used in many of the sample trials presented in this topic. NEWGARDEN can
be used to determine minimal distances into a preserve at which founders
can be placed without risking extensive losses of population growth and
genetic diversity. Such exploratory trials can be used to design less costly
restoration or conservation projects.
Changing the geometric positioning of the same number of founders
(in a square versus a line, or at differing densities), while holding all other
factors constant, can change the number of available offspring safe sites
which can affect population growth rates.
Changing the geometric positioning of the same number of founders
(holding all other factors constant) can affect various population genetics
values, including heterozygosity, loss of unique alleles, frequency of
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