highly significantP < 0.001
marginally nonsignificantP = 0.062
The within-population variation among gut samples ( n = 8 to 12 individuals per population) was marginally nonsignificant (SS = 0.527; pseudo- F = 1.4396, P = 0.062), while the variance between fish populations from different rivers was highly significant (SS = 9.566; pseudo- F = 2.9037, P < 0.001).