We thank G.S. Bever, G.T. Jefferson, and J.I. Mead for comments on earlier versions of the manuscript. We benefitted from discussion about Anza-Borrego Desert leporine taxonomy with M.C. Cassiliano and J.A. White. C.A. Repenning and R.J. Zakrzewski shared their thoughts on arvicoline rodents of the Anza-Borrego Desert, and R.A. Martin provided stimulating discussions of arvicoline evolution in general.