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.