Molecular phylogenetics and diversification of the genus Sporophila (Aves: Passeriformes)

The evolutionary affinities within and among many groups of nine-primaried oscines remain unresolved. One such group is Sporophila, a large genus of New World tanager-finches. Our study focused particularly on clarifying the relationship between this genus and a closely related one, Oryzoborus, and on examining the phylogenetic affinities of the "capuchinos," a group of 11 Sporophila species that share a similar male plumage coloration pattern. Our phylogenetic analyses, based on 498 bp of mitochondrial DNA sequence, indicated that: (1) Oryzoborus is embedded within a well-supported clade containing all Sporophila species, which strongly suggests that both genera should be merged, (2) the species of capuchinos comprise a monophyletic group, implying that the plumage patterns common to all probably arose only once, and (3) the capuchinos clade is comprised of two sub-clades, one including two species that are distributed in northern South America and the other one containing eight species that are present south of the Amazon River. Mean sequence divergence among the southern capuchinos species was extremely low, suggesting a rapid radiation within the last half-million years that may be related to the high level of sexual selection present in the genus and might have been promoted by marine ingressions and egressions that occurred in some southern coastal regions of South America in the Late Pleistocene.