Actual Data versus NEWGARDEN: American Chestnut - Genetic Diversity in Establishing Plant Populations: Founder Number and Geometry - page 269

<Dispersal_Distribution>
<functionpoint x=“0” y=“0”/>
<functionpoint x=“6” y=“0.45”/>
<functionpoint x=“15” y=“0.80”/>
<functionpoint x=“38” y=“0.96”/>
<functionpoint x=“701” y=“1”/>
</Dispersal_Distribution>
and the following pollen contribution distance specifi cations:
<EasyPollen>
<pollenframe low=“0” high=“5” prob=“0.25”/>
<pollenframe low=“6” high=“12” prob=“0.25”/>
<pollenframe low=“13” high=“21” prob=“0.25”/>
<pollenframe low=“22” high=“700” prob=“0.25”/>
<pollenframe low=“701” high=“Inf” prob=“0.0”/>
</EasyPollen>
Figure 16.4 shows how these trial populations grow (graph A) and
change in observed heterozygosity (graph B) through 100 generations
(rounds of mating). When the founders are placed in four separate squares
more distant from the corners (trial b), the population grows slightly faster
than in the indistinguishable trials c and d (founders in one square placed
centrally (trial c) or inset from a corner (trial d)). Placing the founders well
inset by a minimum of 600 grid points from an edge in one square (trial
D) would probably be the most effi cient in terms of distance traveled,
monitoring, care, and other costs, while not sacrifi cing much in terms of
population growth. However, note that trial b appears to be growing at an
increasingly accelerated pace compared to c and d, and thus may expand
much more rapidly over many more generations. Placing the founders
in four separate squares but closer to the border (80 units; trial a) greatly
reduces the rate of growth of the population because of greater losses
by dispersal outside the preserve compared to placing the founders in
separate squares that are inset by 600 units (trial b). Both trials e and f (more
offspring are dispersed closer to the maternal individual; pollen may be
dispersed to greater distances) exhibit reduced growth compared to their
counterpart trials c and d. The greatest difference in population size after
100 generations exists between trials b and f, amounting to approximately
a 47% increase when the balance of offspring dispersal is further from the
carpellate parent. Thus, one strategy to signifi cantly increase population
growth of reintroduced perennial species is manual dispersal of seeds to
greater distances as indicated by NEWGARDEN modeling under dispersal
conditions possessed by trials e and f. All told, the population growth
fi ndings reveal how moderate changes in gene dispersal can affect not only
gene fl ow, but population growth rates.