Researchers at the Universidad Veracruzana (UV), Universidad de Buenos Aires (UBA) and the University of Michigan (UM) are conducting a collaborative project on the genetics of Neotropical primates at the northern and southern edges of their distributions. The main aim of this project is to combine expertise in ecological, genetic and behavioral approaches to understand the taxonomy and evolution of primates in these regions.

This complementary effort started in 2001, when Marta D. Mudry visited field sites in Mexico with members of the UV primate research group, collecting samples from Alouatta palliata and Ateles geoffroyi as part of a cytogenetic project on atelid taxonomy. Dr. Mudry described the karyotypes of these species and identified the presence of different patterns in sex chromosomes from the samples obtained during this trip (Mudry et al., 2001; Nieves and Mudry, 2001; Nieves, 2003; Nieves et al., 2005; Solari and Rahn, 2005). At the same time, Liliana Cortés-Ortiz was using molecular data to examine the phylogenetic relationships and biogeography of the genus Alouatta (Cortés-Ortiz et al., 2003), as well as characterizing the hybridization between Mexican howler monkey species and studying the phylogeography of A. palliata in Mesoamerica (Cortés-Ortiz, 2003). In addition, Ernesto Rodríguez-Luna, Domingo Canales-Espinosa, and Francisco García-Orduña had initiated a long-term study to understand the current distributions of Mexican primates, as well as the sympatry of A. palliata and A. pigra in the state of Tabasco, Mexico (García-Orduña et al., 1999, 2005; Rodríguez-Luna et al., 2001).

For over 25 years, researchers at UV have studied the ecology, physiology and behavior of Mexican primates, including A. palliata mexicana (see Appendix I), A. pigra (e.g., García-Orduña et al., 1999, 2005; Rodríguez-Luna et al., 2001) and Ateles geoffroyi (see Appendix II), and have developed and implemented strategies for their conservation (see Appendix III). Over approximately the same period, researchers of GIBE (Grupo de Investigación en Biología Evolutiva) of UBA have analyzed the cytogenetics of several Neotropical primates, including Alouatta caraya, Aotus azarae, Ateles spp., Callithrix jacchus, Cebus apella, and Saimiri boliviensis (see Appendix IV for a complete listing by species). The GIBE team has used heterochromatic patterns and chromosome rearrangements to elucidate the taxonomy of New World primates (see Appendix IV). More recently, researchers at GIBE have also used biochemical electrophoresis (Szapkievich et al., 1998; Szapkievich, 2000; Szapkievich and Mudry, 2003) and other molecular techniques to characterize populations and to explore the phylogenetic relationships of some of these taxa (Ascunce et al., 2002, 2003a, 2003b). Finally, Liliana Cortés-Ortiz, formerly part of the UV group and now affiliated with UM, is continuing her studies on the systematics and phylogeography of Mesoamerican primates, the genetic characterization of a hybrid zone between A. palliata and A. pigra, the evolution of reproductive isolation in howler monkeys, and the application of molecular approaches to the understanding of primate behavior.

These researchers from UV, UBA and UM are now joining efforts to study the taxonomy and evolution of Neotropical primates using molecular, cytogenetic, ecological and behavioral approaches. Through this collaboration, researchers are currently investigating the heterochromatic pattern and sex chromosome system of A. pigra — the only species of Alouatta whose karyotype has never been studied. This cytogenetic work will be complemented by morphological and molecular characterizations of each sampled individual to verify their identification to species.

These molecular and cytogenetic studies will improve our understanding of the origin and evolution of the exceptionally diverse chromosomal arrangements that occur in howler monkeys (see for example, Ma et al., 1975; Lima and Seuánez, 1991; Consigliere et al., 1996; Rahn et al., 1996; Mudry et al., 2001; Oliveira et al., 2002; Rahn and Solari, 2005). In addition, the cytogenetic study of A. pigra will provide a foundation for the comparison of karyotypes of hybrid and backcrossed A. palliata/A. pigra individuals against the typical karyotype of each parental species.

We expect that this multidisciplinary approach will contribute to the understanding of primate evolution in the Neotropics, as well as establishing a basis for primate conservation in this region. Furthermore, this collaborative project can be a model for combining efforts, expertise, and resources to study primates and other organisms in Latin America.