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.