Amino acid sequences of P1 protamines and the phylogeny of eutherian mammals: a cladistic study

Amino acid and cDNA sequences of eutherian PI protamines, known from publications of other authors, were compared by a cladistic method. Fish, toad and bird protamines were used for the pertinent “outgroup comparisons”, i.e. they provided relevant data for the comparative alignment of the sequences and for the recognition of evolutionary trends. In the sequence positions compared, each amino acid was individually assigned as a plesiomorphic or apomorphic character state (qualitative treatment). The resulting phylogenetic tree (Fig. 2) is only partially in accordance with common ideas on eutherian phylogeny. Disagreements refer to the branching points of Perissodactyla, Lagomorpha and Rodentia.