The Nesospiza finches of the Tristan da Cunha archipelago and Rowettia goughensis from Gough Island, 380. km distant, are both derived from tanager-finches (Thraupidae) that colonized the islands by crossing more than 3000. km of ocean from South America. Sequences from two mitochondrial and four nuclear genes indicate that the Patagonian bridled finches Melanodera are the closest relatives of the South Atlantic finches. Melanodera typically was sister to Rowettia, although some genes linked it more closely to Nesospiza. There was no evidence that Rowettia and Nesospiza are sister taxa, suggesting that the South Atlantic finches evolved from separate colonization events, as apparently was the case for moorhens Gallinula spp. at the two island groups. Genetic divergence between the two island finch genera thus provides an estimate of the maximum period of time they have been present at the islands, some 3-5 million years. A brief review of colonization histories suggests that island hopping by passerine birds is infrequent among islands more than 100-200. km apart.
Bibliographical noteFunding Information:
We thank our colleagues for assistance with field sampling at Tristan and Gough, which was conducted with the permission of the Tristan Administrator and Island Council, through Tristan’s Conservation Department; logistic support was provided by the South African Department of Environmental Affairs and Ovenstones Fishing. We thank the following institutions for providing tissues used in this study: Field Museum of Natural History, American Museum of Natural History, Louisiana State University Museum of Natural Science, Marjorie Barrick Museum of the University of Nevada Las Vegas, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, University of Washington Burke Museum of Natural History and Culture, and the Zoological Museum, University of Copenhagen. Nicholas Beermann performed a portion of the lab work at the University of Minnesota. This research was partially supported by the National Science Foundation ( IBN-0217817 and DEB-0315416 to K.J.B. and DEB-0316092 to S.M. Lanyon and F.K.B.), and the South African National Antarctic Programme.
- Island hopping