Corridors - Genetic Diversity in Establishing Plant Populations: Founder Number and Geometry - page 286

selection (which is more important: population growth or unique allele
preservation or bet hedging?) or interpretation of the history of natural
population diversity.
How does growth rate interact with corridors, population growth, and
genetic diversity retention? Figure 17.8 compares trials in which conditions
are mostly held constant (e.g., annuals; all trials have 20% high corridors that
are 20% of the units on one side of a preserve; pollen and offspring dispersal
are long distance as described above (each frame has outer boundaries four
times as distant as input for basic trial C, with a maximum of 2,804 units)
except as follows:
Trials V and v have the 172 founders placed in a square in the left preserve
only.
Trials W and w have the 172 founders split into two groups, one in each
preserve.
Trials V and W have more rapid growth with r = 1.6.
Trials v and w have slower growth with r = 1.18.
Under the given conditions, trials with founders placed in one square
in one preserve (V and v) have the fastest growth rates across the entire
preserve-corridor-preserve region compared to trials with the equivalent
growth rates but with founders split between preserves (W and w). In terms
of unique allele retention (Fig. 17.8B), the two trials at the higher growth
rate differ by 2.5% (p = 0.01) in allele retention, the trial with founders in
only one preserve (V) retaining the most unique alleles. At the lower growth
rate, and after 40 generations, there is an approximately 587% increase in
retention of unique alleles with placement of founders in only one preserve
(v) compared to placement in two (w). Thus, the pattern seen at the higher
growth rate also occurs at the lower growth rate, but is greatly exacerbated
in the latter case. In previous comparative trials where growth rate was
held constant at the higher level, it was noted that observed heterozygosity
usually differed among treatments by less than 1 to 2%, regardless of
whether the founders were place in one or two preserves, the height of
the corridor, the distance of dispersal, or other variables. In the current
example, this remains true for populations with higher growth rate (Fig.
17.9, trials V and W). However, when growth rate is reduced, there is a
much greater loss of observed heterozygosity when the founders are split
between preserves (v versus w).
In earlier examples, increasing the height of the corridor did not always
have a pronounced effect on population dynamics (e.g., 20% vs 40% high
corridors; short-distance dispersal; r = 1.6; Fig. 17.3) . But, as seen with so
many of the previous examples in this topic, strict rules for general outcomes
are not always applicable. For example, in Fig. 17.10, comparative data
for a series of trials with long-distance dispersal at lower growth rates