Perennials - Genetic Diversity in Establishing Plant Populations: Founder Number and Geometry - page 243

mortality schedules can alter different aspects of population growth and
genetic diversity retention.
The m trial for Lindera benzoin discussed above will be used as the
base trial for the following comparative trials to explore the effects of
age-specifi c mortality. The m trial begins with 172 founders placed in
four squares of 43 founders at each corner of the preserve. Each of these
founders was given the age of “0” at the start of the m trial. A series of
trials were run with input conditions identical to trial m except as follows.
In the following comparative trials (q, r, s, t, and u trials), the founders
establish in this same spatial arrangement but are given an initial age of 13.
This would be equivalent to growing founders from seed in a glasshouse
and then fi eld-planting 172 individuals aged 13. The latter founder age
assignment prevents the early continuing age-specifi c mortality that occurs
for individuals in trial m in which the 172 founders undergo a given rate
of mortality before they reach reproductive age. In trials q through u, the
founders are thus reproductive from the start of the trial runs, and although
mortality proceeds for these founders at the prescribed rates, surviving
founders are generating new individuals from the start, and thus these
populations do not decline in number.
The other major difference between trial m and trials r through u (note:
not for trial q!) is that rates of age-specifi c mortality vary as outlined in Table
15.2. These differences in mortality rates are depicted in Fig. 15.12.
These trial differences in age-specifi c mortality schedules for individual
cohorts can be summarized as follows (and see Fig. 15.12). Trial m is the
basic trial (detailed above in earlier sections on L. benzoin ). Trial q has the
same schedule of mortality although the 172 founders are fi eld-planted
when they are aged 13. Trial r has decreased mortality compared to trial m
for age classes 0 through 7. Thereafter, mortality rates for these two trials are
the same. Trial s has an even steeper decline in early mortality compared to
trial r but then, by age class 10 and thereafter, has a steeply higher level of
mortality for later generations until full mortality at age class 60. Compared
to trials m, q, r, and s, trial t mortality drops to lower rates at age classes 4
through 7 and then steeply increases, but at a rate slightly lower than for trial
s. Finally, trial u has a constantly increasing rate of mortality for successive
age classes, generally exceeding the rates of the other trials.
The effects of these different trial conditions on population expansion
and observed heterozygosity are depicted in Fig. 15.13 , with F values and
unique allele retention given in Fig. 15.14 . First, compare populations m
and q. These trials have all conditions exactly the same, including the age-
specifi c mortality schedules; however, for trial m, all founders are given an
initial age of 0, while for trial q all founders were given an initial age of 13.
Thus, population rounds of replication for the 172 trial q founders begin
at age class 13, since this is their age when planted, and this convention is