Variability in the Electrophoretic Patterns of Avian Serum Proteins

It has been known for more than 50 years that particular proteins characterize every species of plant and animal and that phylogenetic relationships are reflected in protein structure. The first application of this fact to taxonomic studies was by Nuttall ( 1901; 1904) who used the precipitin reaction of immune sera to test degrees of relationship in over 500 species of animals. With refinements in technique have come many more serological studies and the results have justified the statement by Landsteiner (1945) that “chemical differences parallel the variation in structure” and hence are useful in classification. The literattrre on serology is extensive but it has been summarized in the book by Landsteiner ( 1945) and the reviews by Boyden ( 1942 ; 1953). Some of the more recent papers are cited by Stallcup (1954), and Pauly and Wolfe (1957). The development of other methods for protein characterization has suggested that these too might be applied to systematics. Soon after Tiselius (1937) described his apparatus for the electrophoretic separation of colloidal mixtures Landsteiner, Longsworth, and van der Scheer (1938) used it to compare the egg albumins and hemoglobins of five species of birds. Within the next few years there followed the studies by Moore (1945)) Deutsch and Goodloe (1945)) and Deutsch and McShan (1949). These authors investigated the plasma proteins of several species of reptiles, amphibians, fish, birds, mammals, and some invertebrates. They showed that electrophoresis could detect the species specific qualities of proteins and that similarity in proteins paralleled evolutionary relationships. With the development of filter paper electrophoresis the procedure has been simplified and the study of Dessauer and Fox (1956) on the plasma proteins of more than 100 species and subspecies of reptiles and amphibians has been the most extensive to date. Others who have used paper electrophoresis include Zweig and Crenshaw (1957) who found specific characters in the serum proteins of turtles of the genus Pseudemys, and Starr and Fosberg (1958) who published the serum protein patterns of several species of sharks. Woods et al. (1958) used starch gel electrophoresis in a study of the sera of 19 species of invertebrates. The egg white proteins of birds have also been shown to be species specific and to produce excellent electrophoretic profiles. The papers by Bain and Deutsch (1947) and McCabe and Deutsch (1952) are the principal ones to date. The latter reported on 37 species of birds and concluded that the method was applicable to taxonomic problems. Sibley has used paper electrophoresis in a study of the egg white proteins of more than 300 species and has found the conclusions of McCabe and Deutsch fully justified. In 1956, when the senior author began the study described here, the purpose was to determine the uses and limitations of paper electrophoresis in avian taxonomy. Blood serum, rather than egg white, was chosen because of the relatively greater ease of obtaining material. The egg white studies mentioned above were initiated after the work reported here had been completed.