Hypothesis 2- The deer of St. John may have high levels of genetic
diversity due to an infusion of heterogeneous loci in the recent past.
White-tailed deer are one of the most abundant of all New World deer
species, and one that enjoys a pandemic distribution (Heffelfinger
2011). Due to this vast geographic distribution, phenotypic and
genotypic variations exist throughout their range due to either
isolation, phenotypic plasticity, and/or adaptations to local habitat,
forage, and climactic conditions, resulting in 38 recognized subspecies
(Strickland and Demarais 2008; Heffelfinger 2011). In addition,
white-tailed deer have been the been part of domestic and international
restoration and translocation programs that have further increased their
allelic diversity globally. For example, the deer in the state of
Virginia were restocked from deer in eleven separate states, and each
state received hundreds of deer from Wisconsin as part of restocking
programs (Marchinton et al. 1995). Furthermore, the number of alleles
per locus for white-tailed deer were found to be significantly different
from those of mammals in general (Breshears et al. 1998), further
influencing the genetic architecture of deer populations.
The history of the deer on St. John states that additional deer were
brought to St. Thomas and St. John from Texas and the Carolinas in the
1950s as part of a USDA translocation program (Baker 1984; Heffelfinger
2011). Both the Texas and Carolina deer populations are noteworthy in
their levels of genetic heterogeneity either due to geography or
isolation (Erickson 1979; Hillestad 1984). In addition to the Carolina
and Texas deer populations being restocked, the Texas population has not
experienced any kind of a population bottleneck that reduced its allelic
diversity (Erickson 1979; Rhodes and Smith 1992) resulting in a highly
genetically diverse source population. Genetic heterogeneity among deer
populations is generated over short geographical distances, sometimes as
little as 5 km (Sheffield et al. 1985), which is unexpected for this
large and highly mobile species (Smith et al. 2001). As a result, a high
degree of genetic heterozygosity found within deer populations
translates into differences in disease resistance and immune response
among deer subspecies (Gaydos et al. 2002; Johnson et al. 2006).
Therefore, perhaps the genetic diversity of the St. John deer after
approximately 200 years is not as low as expected due to the influx of
highly heterogeneous alleles that came from the infusion of deer from
source populations in Texas and the Carolinas in the 1950s. This
diversity, coupled with the short duration of time since their infusion
into the current population, (approximately 70 years), may have added a
significant amount of genetic diversity of deer currently living on St.
John.