All bootstrapped values for Nei’s D and (δμ)2 were low:
the mean of Nei’s D was 0.007 and the mean of (δμ)2 was 0.744. Comparisons involving Mississippi River Delta, LA,
1997 resulted in the highest values for (δμ)2. These were
due to extremely high values for Pse28 (which averaged
12). In contrast, comparisons involving the 1996 sample
from the same area resulted in the highest values for Nei’s
D (consistent with the results obtained using FST as a
measure of population structure). The neighbour-joining
analysis, based on pairwise comparisons, underscores the
patchy differences we observed (Fig. 4), rather than the
weak large-scale structure indicated in other analyses.
Except for the outlying Louisiana samples (which differed
depending on the assumptions of the mutation model
used for the distance measure), no consistent geographical
pattern emerged