Molecular systematics of the New World monkeys

Abstract

We report here the results of a comparative immunological study of the evolution of primate albumins and transferrins with special reference to the systematics of the New World monkeys. The resulting albumin and transferrin phylogenies are shown to be highly concordant with one another and with data from other laboratories on globin and fibrinopeptide sequences, DNA hybridization, and further immunological studies. We also provide evidence for a probable interdependence of albumin and transferrin rates of evolution which produces a very tight clustering of the total number of amino acid substitutions for the two molecules along lineages of equal time depth, thus providing an even better rationale for the use of these data in the formulation of molecular evolutionary clocks. We again emphasize that the analysis of immunological data is not dependent on non-molecular information or assumptions concerning rates of evolution, and that the analysis provides its own indications of interpretative problems. Specifically we find that the clade Primates must now include Tupaia and Cynocephalus (the “flying lemur”), as well as Tarsius, Anthropoidea, Lemuriformes, and Lorisiformes, and that the New World monkeys share a long period of common ancestry with the Catarrhini subsequent to the divergence of other primate lineages. The catarrhine-platyrrhine divergence is placed at around 35 million years ago, thus strengthening the case for an African derivation of the New World monkeys. The extant New World monkey lineages are then seen as sharing a long period of common ancestry subsequent to that divergence, with their radiation beginning in the early Miocene. From this radiation we see seven equally distinct lineages: (1) Aotus, (2) Callicebus, (3) Cebus, (4) Saimiri, (5) Ateles-Lagothrix-Alouatta, (6) Pithecia-Cacajao, and (7) Callimico-Callithrix-Cebuella-Saguinus-Leontideus. Within those, Ateles with Lagothrix, and Callimico with Callithrix-Cebuella form further subgroups.