Meeting Abstract
Polymorphism has long interested evolutionary biologists as important variation from the standpoint of selection as well as a possible route to speciation. Color polymorphism, in particular, is widespread in many taxa and is important in conspecific interactions, predator avoidance, thermoregulation, and other important functions. Different color variants (such as melanism) may present both costs and benefits to individuals displaying variant phenotypes. While melanistic individuals remain a rarity in some populations, other populations harbor melanism at a relatively high frequency in the absence of an obvious selective benefit. In order to better understand the evolutionary significance of these phenotypes, especially where they persist at high levels, it is important to identify the genetic basis of this variability. Previous work in the gray squirrel, Sciurus carolinensis, identified a 24 base-pair deletion in the melanocortin I receptor gene (Mc1r) that showed a strong association with melanism in introduced populations in the United Kingdom, as well as a small number of individuals from Massachusetts, Virginia, and British Columbia. In this study, we sampled S. carolinensis in Wooster, OH, where melanistic individuals account for ~70% of the local population. Our results confirm that the same Mc1r deletion observed elsewhere is indeed present in the Wooster population. However, our results also suggest that the relationship between the presence of this deletion and the development of melanism may not be as simple as previously thought. Further investigation is necessary to fully understand the genetic basis of this phenotypic variation.
