ATHENS, Ga. - University of Georgia geneticist Dr. John Avise has written the first textbook on 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.
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 professor, Dr. 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 know then that he was on the trail of an entirely new scientific discipline. Intriguing questions kept arising at every turn.
"Over time, many unorthodox perspectives on evolution eventually were to emerge from studies of mitochondrial DNA," said 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 "micro-family tree," tracing organisms back to common ancestors. This would obviously open new vistas in understanding how natural selection affects evolution.
There was another ingredient, 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 so that the study of genetics took a dramatic turn. Together, an entirely new field of study was opening.
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," said Avise. "Just as sons and daughters `inherit' their fathers non-recombined surname [before recent rule changes in some families], so too do progeny normally receive non-recombined mtDNA from their mothers. Furthermore, 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."
A new field of study was opening, but there was only one problem: It didn't have a name. So in 1987, Avise and his colleagues looked around for the right name, 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," said Avise.) They came up with the name "phylogeography," combining geography with "phylogeny," a common scientific term that describes the study of evolutionary genealogy.
The number of journal articles using the term began modestly in the late Eighties, but within a decade, the number was rising geometrically, as one scientist after another around the world began to realize the usefulness–and power–of Avise's concepts.
The field itself, which is brought together in Avise's new book, 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," said Avise.
By 1998, the respected journal Molecular Ecology devoted an entire issue to phylogeography. For his efforts and for other research, Avise had some time before been named a member of the prestigious National Academy of Sciences.
(Writers/Editors: Review copies of Phylogeography may be requested by calling Harvard University Press at 1-800-448-2242.)
WRITER: Phil Williams
CONTACT: John Avise
philwpio@arches.uga.edu
706-542-8501
avise@arches.uga.edu
706-542-1456
News Release