"Evolutionary botany is G. Ledyard Stebbins. He is the discipline. He founded it on his own."
--Betty Smocovitis, professor, University of Florida, Gainesville, in 1988

G. Ledyard Stebbins, whose singular scientific accomplishment was to apply the principles of modern evolutionary biology to plants, died on January 19 at the age of 94.

In her tribute to Stebbins, published in the April 6, 2000, issue of Nature, Betty Smocovitis, professor at the University of Florida, Gainesville, said, "Right up to his death, he demonstrated a resilience and love of the subject [evolution] more characteristic of younger people."

Those who worked with Stebbins, a UC Davis faculty member from 1950 to 1973, observed his sagacity firsthand. Remarks longtime friend and colleague Francisco Ayala, "He was very intense and dedicated. Working in the field, he would pay no attention to the proper time of eating or anything."

Stebbins' intensity is humorously illustrated through stories, many related at his memorial service, about the consequences of his combining field research and driving. An example is the tale of Stebbins driving towards an engrossing plant and straight into a four-foot ditch. Taking no notice of what had happened, he simply got out of the car and walked over to examine the intriguing plant.

Stebbins career in botany began in the early 1920s during his undergraduate years at Harvard University. He began graduate studies there in 1928. At the time, very little was known about the cell; the field of molecular biology didn't exist.

In addition to struggling with gaps in their knowledge about cells, scientists were contentiously reexamining Charles Darwin's theory of evolution in light of the rediscovery in 1900 of Gregor Mendel's work, which proved that traits were transmitted from parents to offspring in discrete units (designated genes in 1909 by the Danish biologist Wilhelm Ludvig Johannsen).

Although Darwin recognized the importance of inheritance to evolution, he didn't have an explanation for how traits were transmitted between generations. Because he, and his contemporaries, didn't know about genes, Darwin couldn't have conceived of genetic mutation as an evolutionary mechanism. He advocated natural selection, whereby nature selects for traits that improve an organism's survival and reproduction, as the process that drives evolution-how things change over time.

During Stebbins' Harvard years, evolutionists were split into two camps. One group believed that new species developed suddenly, due primarily to genetic mutations, and that change occurred in dramatic spurts. Members of the other camp continued to support Darwin's notion that evolution was a gradual process, influenced heavily by natural selection.

Out of the debate there emerged during the 1930s and '40s a new evolutionary theory, and G. Ledyard Stebbins was one of its primary architects.

Dubbed "the modern synthesis" by Julian Huxley in 1942, the new theory essentially incorporated Mendelian genetics into Darwin's theory of natural selection, acknowledging several mechanisms of evolution in addition to natural selection. In the New York Times obituary for Stebbins, Dr. Stephen Jay Gould, evolutionary biologist at Harvard University, described the modern synthesis as "one of the half-dozen major scientific achievements in our century."

What Stebbins did in the 1940s and '50s, and what he continued to do throughout his career, was to figure out how broad evolutionary principles apply to plants, considered by some to be the underdogs in evolutionary biology. "I didn't add any new elements to speak of [to the modern synthetic theory]. I just modified things so that people could understand how things were in the plant world," he said in 1989.

Stebbins knew that plants are often perceived as lacking the charisma of animals, but he thought plants provide easily viewed living proof of what could be called the glory of evolution: diversity. "You can see the diversity just strolling through an area. You don't have to trap plants, search for them, get stampeded by them," he explained.

In 1947 Stebbins spent three months at Columbia University, New York, delivering a series of lectures that, expanded and elaborated, became his groundbreaking book Variation and Evolution in Plants, published in 1950. Betty Smocovitis, history of science professor at the University of Florida, describes Variation and Evolution in Plants as "a synthetic work that brought disparate knowledge from ecology, genetics, systematics, biogeography, and evolution to bear on understanding plant evolution." The Encyclopedia Britannica entry on Stebbins states, "The publication of his Variation and Evolution in Plants established Stebbins as the first biologist to apply the modern synthetic theory to plant evolution."

When awarding Stebbins a 1999 Distinguished Service Award from the American Institute of Biological Sciences, Greg Anderson, the organization's president, commented, "…this book [Variation and Evolution in Plants] is still the one students of plant evolution must read. The second is his [Stebbins'] textbook on chromosome biology, Chromosomal Evolution in Higher Plants. It too stands as a viable and significant reference nearly 30 years after publication."

Shortly after Variation and Evolution in Plants was published, Stebbins came to UC Davis from UC Berkeley, where he had been since 1935, to organize the campus' new genetics department. He created and taught an introductory genetics course and recruited top geneticists such as Francisco Ayala, now Bren Professor of Ecology at UC Irvine, Theodosius Dobzhansky, and Melvin Green. His move to Davis was followed by a shift in his research interests, from population and chromosome biology to developmental biology.

In a tribute to Stebbins given during a national symposium, held earlier this year, that revisited the contributions of Variation and Evolution in Plants, Peter Raven, director of the Missouri Botanical Garden, noted, "And my, how he loved Davis, its growth, its variety, and its accessibility to all. He was proud of his work at Davis, proud of the growing campus as it matured, pleased with his own contributions, and always contented living there."

In addition to his research achievements, Stebbins was a diligent mentor to graduate students, many of whom have become accomplished scientists, and a well-liked teacher of undergraduates. In 1972 he received the campus's Distinguished Teaching Award. "He was a very engaging lecturer, very energetic and enthusiastic, because he knew the subject well and was enamored of it," said Ayala.

For his scientific contributions, Stebbins received a bevy of honors, including election to the National Academy of Sciences in 1952 and the National Medal of Science, received in 1979 from President Carter.

Although he retired in 1973, at age 67, Stebbins stayed active in research and wrote books for another 20 years. He was one of the authors of California's Wild Gardens: A Living Legacy, published in 1996 by the California Native Plant Society for the California Department of Fish and Game. The 248-page book, a guide to California's native plants in their natural setting, credits Stebbins with providing "much of our knowledge about California's rare plants."

In 1980 the Stebbins Cold Canyon Reserve, a 577-acre parcel of protected land set aside for research located about 20 miles west of the Davis campus, was named after the eminent plant evolutionist by the UC Regents. He said that honor was far more satisfying than having his name on a campus building. His ashes were scattered there.

Memorial contributions may be sent to the UC Davis Herbarium. Contributions will fund the G. Ledyard Stebbins student grant program, established in celebration of his 90th birthday, which supports field botany projects that add specimens to the herbarium. Ellen Dean, director of the herbarium, says, "Dr. Stebbins understood that the herbarium is an important tool both for learning plant species and for conserving them. Our specimens are a past and present record of California flora, including extinct species and new weeds. Those wishing to learn more about Stebbins' work are welcome to visit the herbarium, which houses thousands of his specimens." For more information, please contact Ellen Dean, herbarium director, at eadean@ucdavis.edu or (530) 752-1091.