First Comprehensive Examination of the Molecular Phylogenetics of Saki Monkeys, Genus Pithecia Desmarest, 1804, Reveals an Unexpectedly Low Taxonomic Diversity

Saki monkeys ( Pithecia ) are found exclusively in the Amazon, ranging from the Guiana Shield in the east to the Andean foothills in the west. The taxonomy of this genus is complex due to indeterminate type localities, numerous synonyms, sexual dichromatism and considerable geographical diversity in coat colour patterns. Previous assessments have indicated two to four species and a variable few subspecies based on morphological analyses of museum specimens. Just two species have been consistently recognised— Pithecia pithecia and Pithecia monachus . This study presents the first comprehensive molecular phylogeny of the genus, using mitochondrial cytochrome b sequences from 137 individuals across their range and a ddRADseq genomic analysis on 34 individuals. The phylogenetic results revealed three main clades: (1) Guiana Shield sakis, (2) Sedimentary Basin and Brazilian Shield sakis, and (3) a basal P. albicans south of the Rio Solimões. The ddRADseq data further clarified species boundaries and relationships, identifying six distinct species: P. chrysocephala and P. pithecia sensu Hershkovitz (1987) on the Guiana Shield; P. albicans in central Amazonia south of the Rio Solimões; P. monachus in western Amazonia; P. irrorata between the rios Purus, Tapajós, and Juruena; and P. vanzolinii in a limited area east of the Rio Juruá.