OWL MONKEYS (AOTUS) ARE HIGHLY DIVERGENT IN MITOCHONDRIAL CYTOCHROME-C-OXIDASE (COII) SEQUENCES

The evolutionary history and differentiation of the owl or night monke ys (Aotus), remain poorly resolved. Variation in pelage and skeletal m orphology is relatively minor across their broad range, but cytogeneti c studies have revealed that at least 12 karyotypically distinct forms exist, with 2N chromosome numbers ranging from 46 to 58. We obtained DNA samples from three putative species-A. lemurinus, A. nancymae, and A. azarae-and five karyotypes (I, II, III, IV, and VI), amplified the mitochondrial cytochrome c oxidase subunit II gene (COII) via PCR and sequenced ii. Comparisons of the sequences indicate relatively high l evels of sequence divergence among the putative species (4.3 to 6.3%), and suggest that the taxa are genetically quite distinct and have lik ely experienced extended periods of isolated evolution. The levels of COII divergence represent approximately one-third of the levels found between divergent platyrrhine genera, such as Aotus, Saimiri and Calli mico. Using estimates of substitution rates of COII-evolution in homin oid primates, the estimated date of divergence for the Aotus COII sequ ences is 3.6 million years. The Aotus COII data support the existence of multiple species of Aotus, with origins predating late Pleistocene climatic events. Although A. nancymae and A. azarae both live south of the Amazon River and have been considered members of the same species group, phylogenetic analysis of the COII sequences does not support a close relationship between them.