Table 1.

Analysis of Variance for phenotypic traits.

Source of Variation	df	Sum of Squares	Mean Square	F value
ANOVA for shell height
Habitat	1	78.78	78.78	867.61, p < 0.0001
Sample Site	2	18.93	9.46	104.22, p < 0.0001
DNA Pool	8	0.64	0.08	0.88, p = 0.628
error	138	12.53	0.09
ANOVA for shell aperture/shell height
Habitat	1	0.130	0.130	251.32, p < 0.0001
Sample Site	2	0.008	0.004	8.56, p = 0.0018
DNA Pool	8	0.004	0.001	0.874, p = 0.5838
error	138	0.001	0.001

Shell height is the maximum length of the spire of the shell. Aperture/shell height is the maximum width of the aperture divided by the maximum height. There is a significant difference in shell shape for both of these traits between habitats. In the model, we account for variation between lake and river habitats (Habitat), between sites within habitat (Sample site), and among the pools within site (DNA pool).