Scatterplots of genetic and geographical distances separating each
pairwise combination of populations. CA populations are signified by
circles; North American non-CA populations by filled diamonds; and
South American non-CA populations by open diamonds. The regression line
is dotted for CA (P = 0.16, not significant), solid
for non-CA excluding the South American isolates (P
= 0.017, significant), and dashed for non-CA including the South
American isolates (P = 0.362, not significant).