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Evidence for Dominant Inheritance


Indirect Evidence for a Dominant Inheritance of
Brevard, North Carolina’s White Squirrel Variant.

Robert R. Glesener, Heart of Brevard.

Abstract: From a pair released in 1951, Brevard, North Carolina’s white variants have increased to over 1,000 squirrels, currently making up 40.3% of Eastern Gray Squirrels in the study area. For the past 15 years (1997-2011), the community has conducted an annual fall squirrel count. For each I calculated (1) p, the frequency of the white “allele” if dominant, and (2) q, the frequency of the white “allele” if recessive. The p’s and q’s were then plotted separately against time. The slopes of the associated trend lines represent delta-p and delta-q, respectively. Classic population genetic models of change under natural selection solve for delta-p or delta-q in terms of current p, q, and s where s is the selective coefficient. The equations can be algebraically rearranged to solve for s. Plugging in current estimates of p, q, and the deltas obtained above, yields s=.0528 and s=.0745 for the dominant and recessive models, respectively. The initial 1951 frequency of the white predisposing “allele(s)” was ~.0005. Starting at this frequency, I used a computer model to simulate the number of breeding seasons necessary to arrive at the current frequencies. The recessive model requires thousands of breeding seasons. Even if the initial frequency is raised to the unrealistically high level of .02, 662 breeding seasons are required. Under a dominant model, only 124 are necessary beginning at p= .0005. Since gray squirrels have two breeding seasons per year, the actual number available is 61*2=122. This supports the dominant model of inheritance.  NC ACADEMYof SCIENCE 109th Annual Meeting March 23-25 2012, Campbell University: pp 46.

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15 Year Summary of Squirrel CountRelationship between Squirrel Abundance and Mast