INTERSPECIFIC VARIATION AT THE Y-LINKED RPS4Y LOCUS IN HOMINOIDS - IMPLICATIONS FOR PHYLOGENY

Within- and between-species variation in restriction endonuclease reco gnition sites was examined at the Y-linked RPS4Y locus of six hominoid species: human (Homo sapiens), gorilla (Gorilla gorilla), chimpanzee (Pan troglodytes), bonobo (Pan paniscus), orangutan (Pongo pygmaeus), and gibbon (Hylobates lar). RPS4Y is an expressed gene that maps to th e nonrecombining region of the Y chromosome. An approximately 1,490 ba se pair fragment of the RPS4Y gene, including all of intron 3, was amp lified by PCR from DNA extracted from each of the six species. Forty-s even restriction sites were identified on the six-species composite ma p derived from double-digest restriction analyses of the amplified fra gment, As expected, maximum parsimony analysis indicated that chimpanz ee and bonobo are the two most closely related living hominoids. The s ame analysis suggested that the closest living relative of Homo is Gor illa, not Pan, although support for this relationship was relatively w eak. These results disagree with recently published phylogenies based on analyses of mtDNA sequences (Horai et al. [1995] Proc. Natl. Acad, Sci, U.S.A. 88:7401-7404) and the Y-linked ZFY locus (Dorit et al. [19 95] Science 268:1183-1185). A combined data set derived from three dis tinct Y-linked loci-RPS4Y, SRY, and ZFY-was also analyzed. The maximum parsimony topology for the combined data provided only weak support f or a shared common ancestor for Home and Pan subsequent to divergence from the Gorilla lineage. Taken together, the data from the Y chromoso me do not provide unequivocal support for any single, dichotomously br anching species tree linking Home, Pan, and Gorilla. (C) 1996 Wiley-Li ss, Inc.