Conclusions and Discussion - Genetic Diversity in Establishing Plant Populations: Founder Number and Geometry - page 312

trial input conditions. The contribution of cohorts to the trajectories of the
population as a whole can be investigated. Such comparative trials may
be useful in predicting trends in actual populations where census numbers
include several cohorts.
For some situations it may be possible to create comparative trials to
examine the relative contributions of (1) allele loss due to dispersal off a
preserve, (2) the Wahlund effect, and (3) inbreeding to changes in F values
and/or heterozygosity. Such information may be of special importance to
species that are especially sensitive to inbreeding.
NEWGARDEN analyses can be used to compare population growth and
population genetic diversity retention among populations that experience
differing schedules of age-specifi c mortality. Differing mortality rates affect
both the amount of offspring and pollen production, and also the spaces
available for establishment. Seemingly slight differences in mortality may
result in pronounced retention differences. NEWGARDEN trials can be
compared to actual fi eld data to inform restoration or conservation projects
regarding how supplementation, and the spatial arrangement thereof, may
be useful in preserving diversity.
NEWGARDEN analyses can be used to compare population growth and
population genetic diversity retention among populations that experience
differing schedules of age-specifi c rates of reproduction via pollen and/or
offspring production.
NEWGARDEN was used to generate trials that simulated the
approximate life history characteristics and population growth of an
existing stand of long-lived perennials (the American chestnut stand at
West Salem, WI), for which aspects of genetic diversity had already been
studied (Pierson et al. 2007). Results from the NEWGARDEN trials were
similar to DNA marker population genetic data obtained from that stand.
However, potentially, NEWGARDEN modeling output might be compared
with actual fi eld data from a study population with the outcome that little
agreement is found in certain respects. Deviations from NEWGARDEN
predictions would suggest that either NEWGARDEN methods of analysis
are in need of correction or other evolutionary forces than those modeled are
acting on that population. Such fi ndings would be of interest in revealing
improvements that could be made to the NEWGARDEN program (please
contact us), or in revealing aspects of the biology of the study organism
that were not previously considered.
NEWGARDEN analyses support the conclusion that, in general,
annuals and short-lived early successional species should have lower
within-population variation than late successional species (e.g., Loveless
and Hamrick 1984). Individuals of the former are more transient and
disappear before all the variation they possess can accumulate in local
populations. Annuals in particular are more sensitive to recolonization