Hypothesis 1- There may be intrinsic biological traits of the
species, including the potential for rapid population growth and
iteroparity, that alter the expected outcome for genetic loss.
The potential for rapid population growth due to high reproductive
success may have reduced the overall genetic loss to the St. John
population. For example, when released into the forests of St. John upon
their first introduction to the island, the deer experienced an
ecological open niche free from predators, and increased rapidly (Seaman
1966). Despite its small founder population, the St. John deer
population spent a relatively short time period at a small size
(Heffelfinger 2011). This may have allowed the population to largely
retain its genetic diversity because fast population growth minimizes
loss of genetic diversity, assuming high survival and reproductive
success (Kekkonen et al. 2012, Murphy et al. 2015). Thus, the natural
history parameters within deer that allow for high reproductive rates
(e.g., twinning is common and triplets occur with excellent maternal
nutrition), may have altered the genetics of the group over time,
particularly within an environment of with low competition and high food
availability. The second infusion of genes into the population, with the
USDA translocated deer in the 1950s (Baker 1984; Heffelfinger 2011), may
have increased the deer genetic heterozygosity further, but might play a
more minor role than expected because of the allelic retention following
the initial rapid population growth upon their introduction to the
island (Kekkonen et al. 2012).
In addition to the biological potential for rapid population growth for
deer, iteroparity, resulting in overlapping generations, may have also
influenced heterozygosity of the St. John deer (Murphy et al. 2015). In
species with overlapping generations, allelic drift can be lower than in
species without overlapping generations (Kekkonen et al. 2012). This has
been found to be particularly true for individual-based population
genetic models rather than classic population genetics models (Pemberton
1996). Together, rapid population growth and iteroparity may have had an
additive effect in retaining heterozygosity within the population,
resulting in higher allelic reserves than would be predicted for an
isolated island population of deer on St. John for more than 200 years.