Molecular phylogenetics of howler monkeys (Alouatta, Platyrrhini) - A comparison with karyotypic data

Molecular phylogenetic analyses of seven Brazilian Alouatta species, based on cytochrome b DNA sequence data were carried out. Parsimony and neighbor joining topologies grouped Alouatta belzebul and A. fusca as sister groups in one clade while another, well-supported clade contained A. seniculus as the most basal offshoot, followed by A. nigerrima as a sister lineage of A. macconnelli/A. stramineus. Estimates of inter-specific sequence divergence were generally low, and estimates of the time of divergence indicated that the main Alouatta lineages emerged during a short evolutionary interval. A comparison with karyotypic data confirmed the molecular topology showing a closer relationship between A. macconnelli and A. stramineus in respect to A. nigerrima. It also showed that the XX/XY sex chromosome system was main tained in several lineages while the XtX2Y/X1X1X2X2 system appeared indepen dently at least three times during the radiation of howler monkeys. Moreove r, the X1X2Y1Y2/X1X1X2X2 system might have appeared once or, alternatively, twice and independently.