Albumin Evolution in Peromyscus and Sigmodon

Phylogenetic relationships among certain cricetine rodents are examined using the quantitative micro-complement fixation technique. Antibodies against purified albumin from five species of Peromyscus, one species of Sigmodon, and one microtine rodent were used. In addition, serum from nine species of Peromyscus, Ochrotomys nuttalli, and fifteen subspecies and species of Sigmodon were examined. The fourteen species of Peromyscus represent three subgenera. Some, but not all of the results are inconsistent with current classification. The lineages leading to Peromsycus and Sigmodon are estimated to have diverged about 22 million years ago, whereas cricetines and microtines last shared a common ancestor some 40 million years ago.