Phylogenomics of species from four genera of New World monkeys by flow sorting and reciprocal chromosome painting

Background: The taxonomic and phylogenetic relationships of New World monkeys (Platyrrhini) are difficult todistinguish on the basis of morphology and because diagnostic fossils are rare. Recently, molecular data have led to aradical revision of the traditional taxonomy and phylogeny of these primates. Here we examine new hypotheses ofplatyrrhine evolutionary relationships by reciprocal chromosome painting after chromosome flow sorting of speciesbelonging to four genera of platyrrhines included in the Cebidae family: Callithrix argentata (silvered-marmoset), Cebuellapygmaea (pygmy marmoset), Callimico goeldii (Goeldi's marmoset) and Saimiri sciureus (squirrel monkey). This is the firstreport of reciprocal painting in marmosets.Results: The paints made from chromosome flow sorting of the four platyrrhine monkeys provided from 42 to 45hybridization signals on human metaphases. The reciprocal painting of monkey probes on human chromosomes revealedthat 21 breakpoints are common to all four studied species. There are only three additional breakpoints. A breakpointon human chromosome 13 was found in Callithrix argentata, Cebuella pygmaea and Callimico goeldii, but not in Saimirisciureus. There are two additional breakpoints on human chromosome 5: one is specific to squirrel monkeys, and theother to Goeldi's marmoset.Conclusion: The reciprocal painting results support the molecular genomic assemblage of Cebidae. We demonstratedthat the five chromosome associations previously hypothesized to phylogenetically link tamarins and marmosets arehomologous and represent derived chromosome rearrangements. Four of these derived homologous associations tightlynest Callimico goeldii with marmosets. One derived association 2/15 may place squirrel monkeys within the Cebidaeassemblage. An apparently common breakpoint on chromosome 5q33 found in both Saimiri and Aotus nancymae could beevidence of a phylogenetic link between these species. Comparison with previous reports shows that many syntenicassociations found in platyrrhines have the same breakpoints and are homologous, derived rearrangements showing thatthe New World monkeys are a closely related group of species. Our data support the hypothesis that the ancestralkaryotype of the Platyrrhini has a diploid number of 2n = 54 and is almost identical to that found today in capuchinmonkeys; congruent with a basal position of the Cebidae among platyrrhine families.