BATON ROUGE - In a study that sheds light on the origin of bird species in the biologically rich rainforests of South America, LSU Museum of Natural Science Director and Roy Paul Daniels Professor in the Department of Biological Sciences, Robb Brumfield, and an international team of researchers funded by the National Science Foundation, or NSF, published a paper this week challenging the view that speciation - the process by which new species are formed - is directly linked to geological and climatic changes to the landscape.
The researchers, whose findings were published Sept. 10 in the journal Nature, found that the geographic isolation of populations within a single species is more often due to movements of birds across physical barriers, such as mountains and rivers, that occur long after the geological origin of those barriers. Their conclusions not only cast a new light on how the initial step of speciation occurred in tropical birds, but also provide a generalizable explanation for how speciation may be initiated in other regions and in other organisms.
To examine the timing of speciation, the scientists compared genetic patterns among a diverse array of bird lineages that occur in the Neotropics, one of the six major zoogeographical regions of the world extending from Mexico south to the southern most tip of South America known to have more species of birds than anywhere else in the world. Each lineage contained populations situated on the opposite side of large dispersal barriers and, with genetic data, they were able to estimate the time that the populations became isolated from one another. They found that most speciation occurred long after the origin of the Andes and the Amazonian river system.
"By using detailed sampling of many bird lineages, we were able to get a clearer and larger picture of when and how species formed within those lineages. The extraordinary diversity of birds in South America is usually attributed to big changes in the landscape over geological time, but our study suggests that prolonged periods of landscape stability are more important," said Brumfield. "Our results also suggest that human alterations of the landscape can effectively kill the speciation process. If the path to disperse from point A to point B is erased, then there is no way for the initial step of speciation to occur."
"It is probably only in birds that the genetic sampling is sufficiently dense to examine how interactions between the landscape and birds influence the speciation process," he added.
The thousands of samples used in this study represent the culmination of more than 30 years of field expeditions led by generations of LSU students and scientists, plus similar work done by ornithologists at other research institutions.
The mission of the LSU Museum of Natural Science is the acquisition, preservation and study of research collections by museum faculty, staff and students to generate knowledge of regional and global biodiversity, geological history and human history/prehistory for the benefit of the people of Louisiana, the nation and the world. For more information on the museum, visit http://www.
The mission of the Department of Biological Sciences is to create and disseminate new knowledge in the biological sciences through research; to provide for its majors the highest quality, nationally recognized, graduate and undergraduate educational programs; to provide exceptional science training to support the university's general education requirements; and to contribute expertise in support of science education in the community, including the use of available resources to improve K-12 science outreach. For more information, visit http://www.
Other institutions involved in this research include the American Museum of Natural History, City College of New York, Museu Paraense Emílio Goeldi in Brazil, Universidad de los Andes in Colombia, Universidad Central de Venezuela, Colección Ornithológica Phelps, University of California Los Angeles and the University of Georgia Athens.