Shortly thereafter, Collins and Dub

Shortly thereafter, Collins and Dubach (2000b) used DNA sequence data from the mitochondrial control region and cytochromec oxidase subunit II (COII) gene to investigate the phylogenetic
relationships among Ateles. Their research incorporated many of the same putative subspecies and species included in the present study; however, importantly, the western Amazonian form, Ateles belzebuth, was missing from their analysis. Collins and Dubach (2000b) also concluded that the genus could be divided into four distinct clades, but, contrary to the findings of Medeiros
et al. (1997), they argued that A. paniscus was the basal sister taxon to all other spider monkeys and that A. hybridus was closely related to a clade formed by A. fusciceps/A. geoffroyi and A. chamek/A marginatus.
They also argued that A. chamek and A. marginatus did not
represent different groups, at least based on the mitochondrial
regions sequenced in their study, while A. hybridus was suggested
to be a unique phylogenetic lineage. Finally, Collins and Dubach
(2000b) concluded that Ateles geoffroyi and A. fusciceps robustus
were closely related sister taxa, and they thus considered them
to belong to the same species but different subspecies (Fig. 1)
(Collins and Dubach, 2000b).