Spatial Arrangement of Founders - Genetic Diversity in Establishing Plant Populations: Founder Number and Geometry - page 136

an in/out hiking total distance of approximately 80 grid units, than it is to
hike further into the preserve for populations k or q (just hiking to the center
of the preserve in populations v and q involves more than 5,000 grid units
of in/out hiking). Given the variance across these trials and the inevitable
variation involved in actual introduction attempts, and given the much lower
expense of a total in/out hiking distance of 80 grid units for establishing and
maintaining population j, a decision based on a consideration of all factors
may be made that j is the preferred option. Note, however, that population v
experiences the least loss of observed heterozygosity, and the lowest increase
in F, so if inbreeding depression may be a severe problem for a species, a
decision will have to be made about whether inbreeding or unique allele
retention is more important. Further, if it is deemed important that, along
with allele retention, rapid population growth yielding higher numbers of
individuals (e.g., for developing a greater amount of seed for introduction
elsewhere) is also desirable, then planting founders in patterns k or q might
become more attractive. Exploration of other founder placement patterns
may provide better or intermediate solutions.
Although the results above have been couched in terms of experimental
reintroductions, they also have relevance for wild populations founded with
different degrees of subdivision. To give just one example, as succession
proceeds, an old fi eld may initially give rise to a few scattered trees. These
can become perching locations where small clusters of individuals of a bird-
dispersed later-successional tree species can be introduced (e.g., Willson
and Traveset 2001). NEWGARDEN can be used to examine the population
genetics effects of founding populations with varying degrees of clustering
of the founders.
Spatial Effects Conclusions
1. Two populations initiated with the same number of founders and
that experience the same conditions except for the initial spacing of
the founders may grow at different rates due to spatial establishment
effects. These effects will be most intense when establishment for a
species is strongly density dependent, driven by either autogenic or
allogenic forces.
2. The spacing differences can also affect population genetics diversity
parameters differentially, probably because of an interaction of
population growth and patterns of spatial expansion and gene
exchange differences.
3. The effects described in 1 and 2 persist. They are due not just to
initial increase in offspring in the fi rst generation, but to continuing
differences in the numerical and spatial patterning of the developing