RE: J Mol Evol (2006) 61:138–144 — A typographical error appeared in the text of this article. On p. 140, midway down the left-hand column, where it reads:

and variance of X is V(X) = Y (1 − X) / [L (1 − 4X / 3)2] with L equal to the length of the sequence.

it should instead read:

and variance of X is V(X) = X (1 − X) / [L (1 − 4X / 3)2] with L equal to the length of the sequence.

In other words, in the published version the symbol Y should have appeared as an X.