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.