Perennials - Genetic Diversity in Establishing Plant Populations: Founder Number and Geometry - page 228

the maternal plant (trial o). While population growth is slower (Fig. 15.1),
inbreeding and population subdivision are greater ( Figs. 15.2 and 15.3) and
loss of unique alleles is greater ( Fig. 15.4 ) when the founders are broken
into four corner groups. For heterozygosity and unique allele retention, the
differences among trials are not pronounced; for rates of population growth
and level of F, differences can be substantial. Restoration practitioners will
have to weigh the costs and benefi ts of the differing population and genetic
effects versus the various logistical methodologies (e.g., plant closer to a
corner?) when making decisions in developing strategies for reintroducing
a species.
Spicebush Cohorts
Thus far, we have been reporting different spicebush trial statistics for
the entire population that exists and takes part in each round of mating.
However, since spicebush is a perennial, each “generation” of these
populations is composed of individuals originating in numerous different
cohorts, since individuals may belong to cohorts living through 61 rounds
of mating before there is 100% mortality of a particular cohort. However,
results of NEWGARDEN analyses are also reported for each new cohort
of individuals created by each new round of mating so that changes in
cohort characteristics across successive individual cohorts through time can
be tracked. Figure 15.5 depicts size changes in each individual successive
initial cohort through generations in the same virtual expanding populations
for which total population data were reported in Figs. 15.1 through 15.4,
above. For example, for the N population in Fig. 15.5B, approximately 400
new seeds survive in their fi rst year (= the new cohort created by the entire
population, which is composed of surviving individuals from the previous
generations) in the 60th total population round of mating. Some members
of this new cohort have a chance of surviving at most for the next 60 rounds
of mating in this population (that would be to generation 120), although,
because of age-specifi c mortality, different numbers of individuals from
that cohort will randomly die (at rates specifi ed in the “mortality” input
statements) before each subsequent successive round of mating.
For Fig. 15.5A and B, note that cohort 0 has 172 founders for all of
the different trials since this is the number of founders designated by all
of the input fi les. For every trial, the cohorts in initial generations have
successive new cohorts with 0 individuals each, since there is no offspring
production until the founders reach age x = 8 as specifi ed by the input fi les
(see Reproduction_Rate statements for basic trial M given above). Only after
reproduction commences do we see a continuing increase in successive
cohort sizes through age 14 for all trial populations. From age 13 to 14, there