1. Laboratory of Genomic Diversity, National Cancer Institute, Frederick, MD 21702–1201, USA.
2. Mammalian Genetics Laboratory, Advanced BioScience Laboratories, National Cancer Institute, Frederick, MD 21702–1201, USA.
3. Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843, USA.
4. Department of Genetics and Evolution, LaTrobe University, Melbourne, Victoria 3083, Australia.