2.b.iii.Northern-to-Northern Comparisons
In contrast to the Southern populations, when all Northern populations are examined, there is less genetic diversity among them even at large geographic distances. The DAPC analyses further supports that the Northern populations are more similar than Southern populations because the Northeastern and Upper Midwest populations highly overlap in each iteration, only beginning to separate when the Osceola County cluster is removed.
When Osceola County is removed, the top ten differentiating sites for the four large clusters, are mainly differentiating the Northeastern dominated group from the rest. This cluster has the inverse allele frequency to most, if not all, other clusters. All these sites are located on NW024609868.1_scaffold3 and can be found in three annotated genes (LOC8028448, LOC8052187, and LOC8029065). Gene LOC8028448 has been described as collagen alpha chain CG42342, and LOC8029065 has been described as a sphingosine-1-phosphate lyase (Simo et al., 2013). Defining the function of the noted genes in I. scapularis could potentially lead to understanding proximate causation of regionally variable behaviors and inference of selection pressures. Understanding how these variants could potentially impact disease spread is important on an even larger scale, as the Northern ticks are from the historically youngest populations only expanding to the area 20,000-50,000 years ago (Van Zee et al., 2015), and are hypothesized to still be expanding.