UPDATE ON THE PHYLOGENETIC SYSTEMATICS OF NEW-WORLD MONKEYS - FURTHERDNA EVIDENCE FOR PLACING THE PYGMY MARMOSET (CEBUELLA) WITHIN THE GENUS CALLITHRIX

We determined DNA sequences spanning the 1.8-kb long intron 1 of the i nterstitial retinol-binding protein nuclear gene (IRBP) for Callithrix geoffroyi, Callithrix humeralifer, and Callithrix argentata. With the 22 previously determined IRBP intron 1 sequences-21 from the 16 curre ntly recognized genera of New world monkeys-the enlarged IRBP data rep resent for the marmoset genus Callithrix both its argentata and its ja cchus species groups. Maximum-parsimony and neighbor-joining trees, co nstructed for the 25 aligned IRBP intron 1 sequences, support a provis ional phylogenetic classification with three families: Atelidae, conta ining subfamily Atelinae; Pitheciidae, containing subfamily Pitheciina e; and Cebidae, containing subfamilies Cebinae, Aotinae, and Callitric hinae. In order to have taxa at the same hierarchical rank at equivale nt age, this classification has all living callitrichines in a single tribe, Callitrichini, with four subtribes: Saguinina (Saguinus), Calli miconina (Callimico), Leontopithecina (Leontopithecus), and Callitrich ina (Callithrix with the pygmy marmoset, Cebuella pygmaea, merged into it). The DNA evidence shows not only that Callithrix must include C. pygmaea to be monophyletic but also that the times of separation of py gmaea and the argentata and jacchus species groups from one another ar e to be expected (<5 Ma-million years ago) for species in a single gen us. On relating the time course of the ceboid radiation to biogeograph ic information, it appears that in mid-Miocene times (10-11 Ma) a basa l callitrichin stock branched into the ancestral population of Saguinu s in one clade and the ancestral population of Leontopithecus and Call imico-Callithrix (or Leontopithecus-Callimico and Callithrix) in anoth er clade. The proto-lion tamarins migrated south and eastward, where t hey were isolated in refugia, becoming the genus Leontopithecus. The s tock remaining in Amazonia gave rise to present-day Callimico and Call ithrix. The latter genus occupied a vast geographic area, giving rise to the argentata and pygmaea groups in Amazonia and to the jacchus gro up in central and eastern Brazil.