Biology Reference
In-Depth Information
Table 15.2
Age-specifi c mortality rates (y = proportion of the pool of individuals of a given
age that die) for comparative trial model populations of
Lindera benzoin
.
Mortality_Rate = y:
y values for trial:
trials m and q
< Mortality_Rate >
r
s
t
u
<functionpoint x=“0” y=“0.2”/>
0.1
0.1
0.1
0.02
<functionpoint x=“1” y=“0.1”/>
0.05
0.02
0.05
interpolated
<functionpoint x=“4” y=“0.1”/>
0.05
0.05
0.03
interpolated
<functionpoint x=“7” y=“0.05”/>
0.03
0.05
0.02
interpolated
<functionpoint x=“10” y=“0.02”/>
0.02
0.05
0.01
interpolated
<functionpoint x=“45” y=“0.02”/>
0.02
0.8
0.7
interpolated
<functionpoint x=“60” y=“1”/>
1
1
1
1
</ Mortality_Rate >
Trial q (not shown) had the same age-specifi c mortality assignments as trial m, but the 172
founders were aged 13 rather than 0 at the beginning of the trial, as were founders for trials r
through u. The word “interpolated” refl ects the convention that if mortality rates differ between
two age categories that are separated by other non-stated age categories, then mortality rates of
each non-stated age class between those two age classes are interpolated based on the values
given for those two age classes. For example, if rates of mortality are specifi ed for individuals
aged 7 and then aged 10, but not for individuals of intermediate ages, then mortality rates
for individuals aged 8 and 9 will be interpolated based on the aged 7 and aged 10 values.
In the mortality statements, <functionpoint x is the round of mating for which the indicated
mortality rate (the value given for y) applies. For example, for trials m and q, mortality is 10%
for rounds of mating 1 through 4.
depicted as indicated on the graphs. Note that in trial m, since age class 0
founders were introduced, reproduction does not begin for these founders
until several rounds of potential replication (years) have passed, and only
then do the original founders enter reproductive age. Note further that
during this period before reproduction, there is a loss of trial m founders
due to the age-specifi c mortality assigned for early age classes before
reproduction is achieved. For trial q, since the 172 founders are introduced
at reproductive age, such losses of individuals before fi rst reproduction
do not occur, and so population q grows at a faster rate than m through
the following generations. Populations r through u are all like trial q in
that all 172 founders are introduced only when they achieve age class 13
and are reproductive. In comparison to trial m, trial q also suffers less loss
of heterozygosity, less increase in F, and greater unique allele retention,
all attributable to increased pre-reproductive mortality with subsequent
increased inbreeding in population m. These results demonstrate that
even when two introductions have the same rates of age-specifi c, cohort-
specifi c mortalities, nurturing and waiting to plant out founders until they
are reproductively mature (trial q) can greatly infl uence the growth of
populations and the retention of genetic diversity. If individuals are planted
out as seed (trial m), then early investments in preventing mortality of seeds
and seedlings until reproductive age will improve growth and retention.
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