Bibliographical noteFunding Information:
We thank two anonymous reviewers for providing helpful suggestions on an earlier version of this manuscript. This research was funded by the National Science Foundation (DEB-0228682 to R.T.K., E.L.B. and D.W. Steadman; DEB-0228675 to SJH; DEB-0228688 to FHS and DEB-0228617 to WSM). We thank the following collections for tissue samples: American Museum of Natural History, Auckland Museum, Australian National Wildlife Collection, Burke Museum of Natural History and Culture (University of Washington), Field Museum of Natural History, University of Kansas Natural History Museum & Biodiversity Center, L. Densmore private collection, Louisiana State University Museum of Natural Science, Marjorie Barrick Museum (University of Nevada, Las Vegas), Museum of Southwestern Biology (University of New Mexico), Museum of Vertebrate Zoology (University of California, Berkeley), Museum Victoria, National Museum of Natural History, San Francisco Zoological Garden, and Zoological Museum University of Copenhagen.