2.b.iv. Northern-to-Southern Comparisons
Only a few decades have passed since the northern dwelling I.
dammini was assigned as a junior synonym of southern dwelling I.
scapularis (Oliver et al., 1993). Since then, I. scapularis has
been divided into clades to assist in defining the genetic and
phenotypic differences among populations (Goddard et al., 2015; Norris
et al., 1996; Sakamoto et al., 2014). In the population-level DAPC, the
genetic diversity of southern and northern populations is apparent, as
northern populations form one large cluster whereas the southern
populations are distinct. This is further confirmed by the LEA-based
DAPC analysis, in which sample metadata was not input, and each tick was
assigned membership probabilities across five clusters which assorted
into five major regions (Northeast, Upper Midwest, Central, Southern,
and Florida/Southeastern coast). This created three clusters of southern
ticks that do not overlap, and two overlapping clusters of northern
ticks. The breakdown of these clusters is like the subdivisions found
through the microsatellite analysis in Ludwig (2015) and can still be
differentiated as broader Northern and Southern groups. The genetic and
phenotypic differences found among the two groups, and even the five
clusters, warrant further research into genetically defining I.
scapularis populations to better understand how these clades impact
vectorial capacity across the geographic range of I. scapularis .
We were able to identify genomic sites that are correlated to genetic
differentiation of northern and southern populations and have found
regions of the chromosome-scale scaffolds that are highly variable. Both
of which can be used as targets for further phenotypic-focused studies.