Researchers Find Differences Between Galapagos and Mainland Frigatebirds
ScienceDaily (Sep. 29, 2010) — Although the magnificent frigatebird may be the least likely animal on the Galapagos Islands to be unique to the area, it turns out the Galapagos population of this tropical seabird may be its own genetically distinct species warranting a new conservation status, according to a paper by researchers at the Smithsonian Conservation Biology Institute, the Smithsonian's National Museum of Natural History and the University of Missouri-St. Louis published in the scientific journal Proceedings of the Royal Society B.
Researchers at the Smithsonian Conservation Biology Institute conducted three different kinds of genetics tests to determine that the Galapagos population of magnificent frigatebirds has been genetically different from the magnificent frigatebirds elsewhere for more than half a million years. (Credit: Frank Hailer, Smithsonian's National Zoo)
The Galapagos Islands, which once served as a scientific laboratory for Charles Darwin, boast a number of unique plant and animal species, from tortoises to iguanas to penguins. Magnificent frigatebirds, however, can fly hundreds of kilometers across open ocean, suggesting that their gene flow should be widespread and their genetic make-up should be identical to those of the magnificent frigatebirds on the mainland coast of the Americas. Even Darwin predicted that most Galapagos seabirds would not be very different from their mainland counterparts. But researchers at SCBI conducted three different kinds of genetics tests and all yielded the same result -- the Galapagos seabirds have been genetically different from the magnificent frigatebirds elsewhere for more than half a million years.
"This was such a surprise," said Frank Hailer, a postdoctoral research associate at SCBI and lead author of the paper. "It's a great testimony to just how unique the fauna and flora of the Galapagos are. Even something that is so well-adapted to flying over open oceans is isolated there."
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Long-term isolation of a highly mobile seabird on the Galapagos
Frank Hailer1,*, E. A. Schreiber1, Joshua M. Miller1, Iris I. Levin2, Patricia G. Parker2, R. Terry Chesser3 and Robert C. Fleischer1
-Author Affiliations
1Center for Conservation and Evolutionary Genetics, National Zoological Park and National Museum of Natural History, Smithsonian Institution, 3001 Connecticut Avenue NW, Washington, DC 20008, USA
2Department of Biology and Whitney R. Harris World Ecology Center, University of Missouri—St Louis, St Louis, MO 63110, USA
3US Geological Survey, Patuxent Wildlife Research Center, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
*Author for correspondence (hailerf@si.edu, frashai@gmx.net).
Abstract
The Galapagos Islands are renowned for their high degree of endemism. Marine taxa inhabiting the archipelago might be expected to be an exception, because of their utilization of pelagic habitats—the dispersal barrier for terrestrial taxa—as foraging grounds. Magnificent frigatebirds (Fregata magnificens) have a highly vagile lifestyle and wide geographical distribution around the South and Central American coasts. Given the potentially high levels of gene flow among populations, the species provides a good test of the effectiveness of the Galapagos ecosystem in isolating populations of highly dispersive marine species. We studied patterns of genetic (mitochondrial DNA, microsatellites and nuclear introns) and morphological variation across the distribution of magnificent frigatebirds. Concordant with predictions from life-history traits, we found signatures of extensive gene flow over most of the range, even across the Isthmus of Panama, which is a major barrier to gene flow in other tropical seabirds. In contrast, individuals from the Galapagos were strongly differentiated from all conspecifics, and have probably been isolated for several hundred thousand years. Our finding is a powerful testimony to the evolutionary uniqueness of the taxa inhabiting the Galapagos archipelago and its associated marine ecosystems.
Galapagos endemism, microsatellites, morphological differentiation, mtDNA, nuclear introns, philopatry
Frank Hailer1,*, E. A. Schreiber1, Joshua M. Miller1, Iris I. Levin2, Patricia G. Parker2, R. Terry Chesser3 and Robert C. Fleischer1
-Author Affiliations
1Center for Conservation and Evolutionary Genetics, National Zoological Park and National Museum of Natural History, Smithsonian Institution, 3001 Connecticut Avenue NW, Washington, DC 20008, USA
2Department of Biology and Whitney R. Harris World Ecology Center, University of Missouri—St Louis, St Louis, MO 63110, USA
3US Geological Survey, Patuxent Wildlife Research Center, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
*Author for correspondence (hailerf@si.edu, frashai@gmx.net).
Abstract
The Galapagos Islands are renowned for their high degree of endemism. Marine taxa inhabiting the archipelago might be expected to be an exception, because of their utilization of pelagic habitats—the dispersal barrier for terrestrial taxa—as foraging grounds. Magnificent frigatebirds (Fregata magnificens) have a highly vagile lifestyle and wide geographical distribution around the South and Central American coasts. Given the potentially high levels of gene flow among populations, the species provides a good test of the effectiveness of the Galapagos ecosystem in isolating populations of highly dispersive marine species. We studied patterns of genetic (mitochondrial DNA, microsatellites and nuclear introns) and morphological variation across the distribution of magnificent frigatebirds. Concordant with predictions from life-history traits, we found signatures of extensive gene flow over most of the range, even across the Isthmus of Panama, which is a major barrier to gene flow in other tropical seabirds. In contrast, individuals from the Galapagos were strongly differentiated from all conspecifics, and have probably been isolated for several hundred thousand years. Our finding is a powerful testimony to the evolutionary uniqueness of the taxa inhabiting the Galapagos archipelago and its associated marine ecosystems.
Galapagos endemism, microsatellites, morphological differentiation, mtDNA, nuclear introns, philopatry
Received July 8, 2010.
Accepted September 2, 2010.
© 2010 The Royal Society
Accepted September 2, 2010.
© 2010 The Royal Society
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