INTERGENERIC RELATIONSHIPS OF THE NEW-WORLD-JAYS INFERRED FROM CYTOCHROME-B GENE-SEQUENCES

The six genera of corvids endemic to the Americas (i.e., Aphelocoma, C alocitta, Cyanocitta, Cyanocorax, Cyanolyca, and Gymnorhinus) form the assemblage that most ornithologists call the New World jays. The inte rgeneric relationships among these six genera are explored using compl ete sequences from the cytochrome b gene (1,143 bp) along with 29 morp hological characters. A consistent phylogenetic hypothesis was obtaine d when the data sets were analyzed independently or in a total evidenc e approach. The phylogeny presented in this paper does not corroborate the existence of two evolutionary lineages as previously proposed by Hardy (1961, 1969). The most basal genus of the New World jays is Cyan olyca, which also is supported by independent evidence on cranial anat omy. The remainder of the genera are embedded within two major clades. The most derived is formed by Cyanocitta, Aphelocoma, and Gymnorhinus , being Cyanocitta the most basal genus within this clade. Calocitta a nd Cyanocorax constitute the other clade. A very close relationship be tween these two genera is supported by bootstrap values and branch sup port analysis. These results corroborate the hypothesis that the Pinon Jay (Gymnorhinus cyanocephalus) is a true New World jay, and a putati ve relationship with nutcrackers is not supported. The phylogeny obtai ned is used to infer a biogeographic scenario, as well to explain the evolution of a very derived jaw articulation present only in the New W orld jays. The biogeographic scenario agrees with a relatively recent arrival of a corvine ancestor via Beringia, and a very rapid dispersal and radiation into the Americas.