Cytogenetic variability within and across populations of Cebus apella in Argentina.

Two geographically separated populations of Cebus apella are found in Argentina. We have found important differences in the phenotypic characteristics of these populations, despite marked karyotypic similarity. Two well-distinguished phenotypes were established. Individuals from the northwest of Argentina are phenotypically similar to the Paraguayan populations and are recognized as C. apella paraguayanus. This subspecies is also found in the northeast of Argentina. Other specimens from the northeast are more similar phenotypically to the Brazilian subspecies C. apella nigritus and C. apella libidinosus and are designated as C. apella vellerosus. The two subspecies C. apella paraguayanus and C. apella vellerosus share the same diploid number of chromosomes (2n = 54). Cytogenetic comparisons using G-, Q- and R-banding techniques and C-banding methods with the chromosomes carrying large heterochromatic blocks (No. 3, 5, 11, 12, 13, 19) showed differences between the subspecies. The presence of different polymorphisms and even of heteromorphisms in the same chromosomic pair across geographically isolated populations of the same subspecies is illustrated with Argentinian and Paraguayan specimens.