EVOLUTION OF THE WINGED
Researchers leading efforts to establish the evolutionary history of birds

In 1999, an encephalitis-like viral infection emerged in people living in the New York region and was first suspected to be the St. Louis encephalitis virus, which was found to be associated with a high mortality in wild and domesticated birds. After being linked to numerous human deaths and after careful study, the New York outbreak was determined by health workers to be different from the St. Louis encephalitis.

The New York strain was most closely related to a similar strain found in dead birds in Israel, East Africa, and eastern Europe. Understanding where the virus came from and what birds were infected with it provided health officials with the knowledge they needed for diagnosis, predicting its spread, and minimizing human and animal infection.

To further understand bird evolution, ecology and behavior, LSU ornithologist Fred Sheldon is leading a $2 million study that will map out the evolutionary relationships of our avian friends. The study is part of a larger inquiry launched by the National Science Foundation known as the Assembling the Tree of Life program, which aims to construct the evolutionary history, or phylogeny, for the more than 1.7 million described species of life.

“If you want to understand how organisms are related, there is only one way to do that,” says Sheldon, director of the LSU Museum of Natural Science and the George H. Lowery, Jr. Professor of Natural Sciences. “You’ve got to build a tree.”

He and his colleagues are doing just that. With collaborators at the Field Museum in Chicago, the Smithsonian National Museum of Natural History, Wayne State University, and the University of Florida, researchers at the LSU Museum of Natural Science are piecing together large amounts of DNA sequence data for all major avian lineages to construct an actual tree of bird evolutionary history—much like people do with family trees. In total, there are 30,000 base pairs of DNA of 300 species of birds being used to construct the avian tree of life.

Using lab techniques like PCR, or polymerase chain reaction, technology on tissue samples, researchers can take a single gene, make copies of it, and obtain a DNA sequence of each sample. Sequences from various bird species are compared to determine similarities and differences, which, in turn, determine where on the evolutionary history tree a particular species will fall.

Because genes carry a history of the species with them, Sheldon and his team can determine how ducks and chicken-like birds are related or why ostriches evolved to be flightless or why warblers migrate each winter to South America. They will repeat the process of analyzing bird genetic data until the tree is complete, which will give us a better understanding of the history of birds and allow us to better respond to viral attacks like the one in New York in 1999.

ON THE WEB:
LSU Museum of Natural History

from Fall 2006 Issue