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By Phil Williams
pwilliam@franklin.uga.edu
UGA geneticist John Avise has written the first textbook in a field that he helped to found and develop. His book, Phylogeography: The History and Formation of Species, is about the geographical distribution of genealogical lineages and was just published by Harvard University Press.
 “Science is often serendipitous,” says Avise. “Shortly after joining the University of Georgia in 1975, I gave a departmental seminar describing work on protein variation in fish. Echoing a sentiment popular at the time, I concluded that regulatory rather than structural genes should be studied next, because changes in gene regulation were perhaps at the heart of adaptive evolution.”
He asked the audience how he might examine regulatory genes, and one researcher asked Avise if he’d considered using restriction enzymes to assay such pieces of DNA.
Restriction enzymes are chemicals that naturally cut DNA in certain places. Knowledge of them was so new in 1975 that Avise had never even heard of them. He found one faculty member, Robert Lansman, who knew about restriction enzymes, but his work was not on regulatory genes. Instead, Lansman studied the DNA of mitochondria, tiny cell-bound packages that generate energy for the cells.
Soon, Avise was deep in the study of mitochondrial DNA (mtDNA), mainly as a training exercise. He didn’t realize that he was on the trail of an entirely new scientific discipline--but intriguing questions kept arising at every turn.
“Over time, many unorthodox perspectives on evolution eventually were to emerge from studies of mitochondrial DNA,” says Avise, “but years would pass before relatively clear answers to some of the questions would be forthcoming.”
By the late 1970s, the study of mtDNA was generating considerable excitement in laboratories around the world. Early on, Avise had the idea that mtDNA might be a wonderful tool for analyzing the evolution of certain vertebrates. Scientists knew that mtDNA was passed down through maternal lineages, so they realized that they could construct a kind of “family tree,” tracing organisms back to common ancestors. This would obviously open new vistas in understanding how natural selection affects evolution.
There was a further possibility, however. Avise realized that the study of mtDNA could be used to map the geographic distribution of gene lineages. At about the same time, powerful new techniques for replicating strands of DNA became practical, and the study of genetics took a dramatic turn.
A casual conversation with another scientist over lunch brought things into sharper focus for Avise. He was explaining his laboratory’s recent findings on modes of inheritance and patterns of geographical variation in mtDNA for small mammals. Avise’s colleague remarked that this seemed analogous to the surname evolution in human societies.
“This simple comment struck home and helped greatly in my otherwise torturous transition from Mendelian to phylogenetic thinking,” says Avise. “Just as sons and daughters ‘inherit’ their father’s non-recombined surname [in the U.S. cultural tradition], so too do progeny normally receive non-recombined mtDNA from their mothers. Furthermore, in much the same way that mutations sometimes arise in surnames--my own name was a 19th-century misspelling of ‘Avis’--point mutations occasionally arise and cumulatively differentiate related mtDNA genotypes.”
In 1987, Avise and his colleagues began looking for the right name for this new field of study, knowing that--in science as in everything else--the right term is crucial to the spread of information. (The term “biodiversity,” for example, had an enormous impact upon the spread of ideas relating to “biological variety as a cherished resource,” says Avise.) They came up with “phylogeography,” combining geography with “phylogeny,” a common scientific term that describes the study of evolutionary genealogy.
Journal articles using the term began to appear in the late 1980s, and within a decade use of the term was rising geometrically, as one scientist after another around the world began to realize the usefulness and power of Avise’s concepts. In 1998, the respected journal Molecular Ecology devoted an entire issue to phylogeography.
The field combines the sciences of molecular genetics, population genetics, ethology, demography, phylogenetic biology, paleontology, geology and historical geography.
“Phylogeography is an integrative endeavor that lies at the important crossroads of diverse evolutionary disciplines,” says Avise.
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