2.a. Variation within populations
Genetic variation is abundant within all populations, but Northern and
Southern populations have noticeable differences when individual
populations are analyzed. Northern populations have slightly less
inbreeding and slightly higher allelic richness on average than
individual Southern populations, potentially indicating that Northern
populations are interbreeding across larger distances, creating more
genetically cohesive units across the northern U.S. The higher levels of
allelic richness are also believed to be a good indicator of a
population’s ability to adapt to future environmental changes (Caballero
& Garcia-Dorado, 2013), further supporting the hypothesis that Northern
populations are leading the geographic expansion of I. scapularisin North America. Meanwhile, populations at the dividing boundaries of
our quadrants (e.g., North Carolina and Ohio) have the highest levels of
allelic richness, likely resulting from the Northern and Southern
genetic groups interbreeding in these areas. In contrast, Southern
populations have higher degrees of inbreeding, indicating there is less
gene flow occurring among collection localities sampled in the south,
creating more distinctive genetic groups.