The Neotropical Primate Adaptation to Nocturnality

Abstract

The only primate with a nocturnal lifestyle in the neotropics is Aotus, the owl monkey. The genus is found from Panama to northern Argentina, and is very diverse. Twelve karyotypically distinct forms have diploid chromosome counts ranging from 46-58 (Hershkovitz, 1983; Ma et al., 1985; Pieczarka et al., 1993) and recent morphological and molecular analyses support the taxonomic division into multiple species (Ford, 1994; Ashley and Vaughn, in press). The fossil record suggests that Aotus is an ancient taxon with a long period of adaptation to nocturnality (Setoguchi and Rosenberger, 1987). Morphologists have placed Aotus together with Callicebus (Ford, 1994; Hartwig, 1995), but some recent molecular and morphological analyses place Aotus within the pitheciine group (Rosenberger, 1995; Schneider and Rosenberger, this volume), with Saimiri and Callicebus (Kay, 1994), or with the callithrichid group. The difficulties of classifying Aotus within the Neotropical primates may be a result of its many primitive traits.