1P value based on comparison of variance components
with null distribution created with 1000 random permutations of the
distance matrix. In both lakes, the variation between sampling dates was
greater than expected by chance, but only significantly greater in
Little Appleton.
For both outbreaks, there were multiple cases where a particular
parasite genotype was identified on multiple sampling dates (Figure 2 A
& B), indicating persistence of some genotypes through time. Indeed,
some genotypes were present throughout the entire sampling period (e.g.,
the genotype labeled ‘3’ in panel C was found on all but one of the
sampling dates, and genotype ‘4’ was found in late July and early
October). However, despite this persistence of some genotypes throughout
the study, genetic distance between P. ramosa populations at
different sampling dates increased with the time between sampling
(Little Appleton: F1,13=8.41, P=0.012; Crooked:
F1,13=20.99, P<0.001; Figure 2 C & D). For
parasites in Little Appleton, this change was driven mostly by the large
genetic distance between genotypes at the beginning of the outbreak and
genotype composition on the rest of the sampling dates (Figure 2 C),
whereas in Crooked, genetic distance between populations increased more
steadily as time between sampling dates increased (Figure 2 D).
Interestingly, three genotypes (‘4’, ‘9’, and ‘11’ in Figure 2 A&B)
were found in both Little Appleton and Crooked.