1. School of Mathematics and Natural Sciences; Arizona State University; PO Box 37100 Phoenix AZ 85069 U.S.A.
2. Colorado Plateau Research Station and Department of Biological Sciences; Box 5614, Northern Arizona University; Flagstaff AZ 86011 U.S.A.
3. Department of Biology; Stephen F. Austin State University; P.O. Box 13003 Nacogdoches TX 75962 U.S.A.