Colonization of South America from Caribbean Islands Confirmed by Molecular Phylogeny with Increased Taxon Sampling

Abstract

A previous phylogeny of New World orioles (Icterus) suggested a possible example of island-to-mainland colonization. Using two mitochondrial genes (cytochrome b and ND2), that study showed that 43 of the recognized species/ subspecies are divided into three clades (A, B, C). Because of a lack of fresh tissue, however, two key taxa—the South American Orange-crowned Oriole (I. auricapillus) and the Caribbean Hispaniola Oriole (I. dominicensis dominicensis)—were missing from that analysis. To complete the phylogeny, we sequenced both genes for these taxa and reconstructed a well-supported phylogeny via parsimony and maximum-likelihood analyses. The addition of I. d. dominicensis to the phylogeny confirms that the Greater Antillean Oriole (I. dominicensis) is polyphyletic, and taxonomic revision of this species complex is warranted. Also, the placement of I. auricapillus and I. d. dominicensis within clade A has important implications for biogeography. The revised phylogeny implies that clade A orioles colonized mainland South America from Caribbean islands. Orioles thus provide a striking example of reverse colonization that contradicts the traditional assumption in island biogeography of mainland-to-island colonization.