COMPARATIVE KARYOLOGY AND EVOLUTION OF THE AMAZONIAN CALLITHRIX (PLATYRRHINI, PRIMATES)

Chromosomal studies in three species of Amazonian Callithrix (2n=44) a nd data in the literature show that this group is karyomonotypic. More over, it is characterized by the presence of abundant heterochromatic regions, unlike the situation in congeneric forms of Callithrix of the Atlantic coast with 2n=46, and by the presence of a highly repetitive , exclusive DNA component, with a basic repeat motif of 1528 bp. Karyo typic comparisons with other Callitrichids and an outgroup species sho wed that Callitrichids are karyologically conserved and explained seve ral rearrangements that had presumably occurred during their phyletic radiation. Analyses of karyologic data enabled the construction of two alternative phylogenetic topologies. The lack of derived homoeologies , common to all members of the genus Callithrix grouped at present, an d the fact that Amazonian species were more similar to Cebuella pygmae a (2n=44) than to their congeneric forms with 2n=46 suggested that spe cies at present included in the Amazonian Callithrix should be grouped with C. pygmaea.