G. Ledyard Stebbins
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George Ledyard Stebbins, Jr. (January 6 1906 — January 19 2000) was an American botanist and geneticist who is widely regarded as one of the leading evolutionary biologists and botanists of the 20th century.[#endnote_NYT] Stebbins received his PhD in botany from Harvard University in 1931. He went on to the University of California, Berkeley where his work with E. B. Babcock on the genetic evolution of plant species and his association with a group of evolutionary biologists known as the Bay Area Biosystematists, led him to develop a comprehensive synthesis of plant evolution. His most important publication in this regard was Variation and Evolution in Plants, which combined genetics and Darwin's theory of natural selection, and is considered to be a major contribution to modern evolutionary synthesis.
From 1950, Stebbins was instrumental in the establishment of the Department of Genetics at the University of California, Davis. He was active in numerous organizations involved in the promotion of evolution, and science more generally, and was elected to the National Academy of Science. He was also involved in the development of evolution-based science programs for Californian high schools, and the conservation of rare plants in that state.
Early life and education
Stebbins was born in Lawrence, New York, the youngest of three children. His parents were George Ledyard Stebbins, a wealthy real estate financier who developed Seal Harbor, Maine and helped to establish Acadia National Park, and Edith Alden Candler Stebbins; both parents were native New Yorkers and Episcopalians. Stebbins was known throughout his life as Ledyard, to distinguish himself from his father. The family encouraged their sons’ interest in natural history during their periodic journeys to Seal Harbor. In 1914, Edith contracted tuberculosis and the Stebbins moved to Santa Barbara, California to improve her health. In California Stebbins was enrolled at the Cate School in Carpinteria.
After graduating from high school, Stebbins embarked on a major in political studies at Harvard. He planned to peruse a career in law, following in the footsteps of his elder brother Henry. By the third year of his undergraduate study, he decided to major in botany, despite his parents disapproval. He started graduate studies at Harvard in 1928, initially working on flowering plant taxonomy and biogeography—particularly that of the flora of New England—with Merritt Lyndon Fernald. He competed his MA in 1929 and continued to work toward his PhD. Stebbins became interested in using chromosomes for taxonomic studies, a method that Fernald did not support. Stebbins chose to concentrate his doctoral work on the cytology of plant reproductive processes, in the genus Antennaria, with cytologist E. C. Jeffrey as his supervisor and Fernald on his supervisory panel. During his PhD candidature, Stebbins sought advice and supervision from geneticist Karl Sax. Sax identified several errors in Stebbins work and disapproved Stebbins interpretation of results which while in accordance with Jeffery's views, were inconsistent with the work of contemporary geneticists. Jeffrey and Sax argued over Stebbins's dissertation, and the thesis was revised numerous times to accommodate their differing views.
Stebbins's PhD was granted by Harvard in 1931. In March that year, Stebbins had married Margaret Chamberlin; together, they would have three children. In 1932 Stebbins took a teaching position in biology at Colgate University. While at Colgate he continued his work in cytogenetics, in particular he continued to study the genetics of Antennaria and began to study the behaviour of chromosomes in hybrid peonies bred by biologist Percy Saunders. Saunders and Stebbins attended the 1932 International Congress of Genetics in Ithaca, New York. Here, Stebbins's interest was captured by talks by Thomas Hunt Morgan and Barbara McClintock, who spoke about chromosomal crossover. Stebbins repeated McClintock's crossover experiments in the peony, published several papers on the cytogenetics of Paeonia, which established his reputation as a geneticist.
UC Berkeley
In 1935, Stebbins was offered a genetics research position at the University of California, Berkeley working with geneticist E. B. Babcock. Babcock needed assistance with large Rockefeller-funded project characterizing the genetics and evolutionary processes of plants from the genus Crepis. Babcock was interested in developing Crepis into a model plant, to enable genetic investigations similar to those possible in the model insect Drosophila melanogaster. Like the genera that Stebbins had previously studied, Crepis commonly hybridized, displayed polyploidy (chromosome doubling) and could make seed without fertilization (a process known as apomixis). Babcock and Stebbins had a productive collaboration, producing numerous papers and two monographs. The first, published in 1937, was on the reclassification of the Asiatic Crepis species into the genus Youngia. The second, which was published in 1938, The American Species of Crepis: their interrelationships and distribution as affected by polyploidy and apomixis. This mongraph was described by Swedish botanist Åke Gustafsson as the most important work on the formation of species during that period.[#endnote_Gustafsson]
In the Crepis monograph, Babcock and Stebbins described the polyploid complex and its role in plant evolution. Some genera, such as Crepis, have a complex of reproductive forms that center on sexual diploids that have also given rise to polyploids; sometimes, as in Crepis, these are apomictic polyploids. Apomictic polyploids are able to perpetuate unbalanced polyploid types, such as triploids and pentatetraploids, which would be sterile if they had to sexually reproduce. Babcock and Stebbins also observed that polyploid types always have a wider distribution than diploid species, and proposed that polyploids have a greater potential to exploit varied environments, because they inherit all traits from both parents. Their observations offered insight into species formation and knowledge of how all these complex processes could provide information on the history of a genus. Stebbins's review "Types of polyploids: their classification and significance" published in American Naturalist in 1940, synthesized the literature on polyploidy and is considered a classic in the field.[#endnote_AN]
In 1939,with Babcock's support, Stebbins was made a full professor in the Department of Genetics at UC Berkley, after failing to be promoted by the Department of Botany. Stebbins was required to teach a course on evolution, and during his preparation he became excited by contemporary research combining genetics and evolution. He became associated with a group known as the Bay Area Biosystematists, which included botanist Jens Clausen, taxonomist David Keck, physiologist William Hiesey and the evolutionary geneticist Theodosius Dobzhansky. With the encouragement of this group of scientists, Stebbins directed his research towards evolution. He became involved with the Society for the Study of Evolution in 1946, and was one of the few botanists involved with the organization.
His research on plant evolution also progressed during this period; he worked on the genetics of forage grasses, looking at polyploidy and the evolution on the Poaceae and publishing numerous papers on the subject though the 1940s. He produced an artificial autotetraploid grass from the diploid species Ehrharta erecta through treatment with the chromosome doubling agent colchicine. He was able to establish the plant in the field, and after 39 years of field trials was able to show that the autotetraploid was inferior to its diploid parent; thus, he linked the success of polyploid species to habitat change.[#endnote_stebbin1985]
In 1946, Stebbins was invited to present Columbia University's prestigious Jesup Lectures, on Dobzhansky's recommendation. In 1941, Edgar Anderson, whos work on hybridization in the genus Iris had interested Stebbins since they met in 1930, and Ernst Mayr copresented the series. Mayr later published his lectures as Systematics and the Origin of Species, which became one of the cornerstone publications of the modern evolutionary synthesis. Stebbins's 1946 lectures drew together the otherwise disparate fields of genetics, ecology, systematics, cytology, and paleontology. In 1950, the lectures were published as Variation and Evolution in Plants, which proved to be one of the most important books published in 20th-century botany; in this book, Stebbins presented a comprehensive synthesis of evolution. The book brought botanical science into the new synthesis of evolutionary theory, and became part of the canon of biological works written between 1936 and 1950 that formed the modern synthesis of evolution. Following its publication, Stebbins was regarded as one of the experts on modern evolutionary theory and is widely credited with the founding of the science of evolutionary botany.
UC Davis and later life
Stebbins took an appointment at the University of California, Davis in 1950, where he was a key figure in the establishment of the University's Department of Genetics. The focus of his research moved to incorporate newer areas, such as developmental morphology and genetics in crop plants, including barley. During his tenure at UC Davis, he trained more than 30 graduate students in genetics, developmental biology and agricultural science. His own broad research interests included the study of a wide range of plants, and he published extensively in systematics, morphology, cytology, genetics, plant geography and developmental biology, in addition to numerous reviews discussing the research of his contemporaries. Stebbins wrote several books during his time at UC Davis. These included Processes of Organic Evolution, The Basis of Progressive Evolution, and his follow-up to "Variation and Evolution", [[Flowering Plants: Evolution Above the Species Level]] was published in 1974 following his delivery of the Prather Lectures at Harvard. He wrote Chromosomal Evolution in Plants and the textbook Evolution with co-authors Dobzhansky, Francisco Ayala and James W. Valentine. His final book was Darwin to DNA, Molecules to Humanity was published in 1982.Stebbins was passionate about teaching evolution, and during the 1960s and 70s he was a vocal advocate for the teaching of Darwinian evolution in schools. He worked closely with the Biological Sciences and Curriculum Study to develop high school curricula l based on evolution as the central unifying principle in biology. Stebbins was active in numerous science organizations—including the International Union of Biological Sciences, the Western Society of Naturalists, the Botanical Society of America, and the Society for the Study of Evolution—and served as President of the American Society of Naturalists. He was elected to the National Academy of Sciences in 1952. Stebbins received numerous awards for his contributions to science: the National Medal of Science, the Gold Medal of the Linnean Society of London, the Addison Emery Verrill Medal from the Yale Peabody Museum, and the John Frederick Lewis Award from the American Philosophical Society.
Stebbins was active in conservation issues in California during his later life. He established the California Native Plant Society branch in Sacramento in the early 1960s. Through the society, he created an active field trip program to increase interest in the native flora of California and to document rare plants. Stebbins was the state President of the Society in 1966. The society was instrumental in preventing the destruction of a beach on the Monterey Peninsula that he referred to as "Evolution Hill"—the area is now known as the S.F.B. Morse Botanical Area. He was instrumental in the establishment of the Inventory of Rare and Endangered Vascular Plants of California, which is still used by state and federal bodies in the United States for conservation policy-making.[#endnote_Faber] He was a major contributor to the Society's 1996 book California's Wild Gardens: A Living Legacy. In 1980, the University of California, Davis, named a parcel of land of 2.33 km² near Lake Beryessa, California, the Stebbins Cold Canyon Reserve, in recognition of his contributions to conservation and evolutionary science. The reserve is a part of the University of California Natural Reserve System.
In 1973, Stebbins gave his last lectures at UC Davis, he was made emeritus professor, and following his retirement traveled widely, taught and visited colleagues for another for the next 20 years. His last paper, "A brief summary of my ideas on evolution", was published in the American Journal of Botany in 1999, in the same year he was co-recipeint with Ernst Mayr of the Distinguished Service award from the American Institute of Biological Sciences. A colloquium was held by the National Academies of Science in 2000 to commemorate the 50th anniversary of the publication of Variation and Evolution in Plants. Following a cancer-related illness, Stebbins died in his home in Davis in that year. Stebbins was honored at a Unitarian memorial service—he had been active in the church in his later years following marriage to his second Barbara Monaghan Stebbins in the 1950s.[#endnote_AnnuRevGenetics] His ashes were scattered at Stebbins Cold Canyon Reserve.[#endnote_Wright]
Legacy
Stebbins made an enormous contribution to the literature of plant evolutionary biology, in addition to his seven book, he wrote more than 280 journal articles and book chapters, a compilation of which were published in 2004, The Scientific Papers of G. Ledyard Stebbins (1929–2000). Biographer Smocovitis, a history of science academic who is preparing a full-length biography on Stebbins,[#endnote_VSBbio] has described Stebbins's scientific strength as follows.His ability to read quickly, recognize novel insights, digest new material, and then integrate the knowledge were the hallmarks of his scientific work style. He was a masterful synthesizer and master of the review essay or synthetic thought piece.[6]
The UC Davis Herbarium maintains a G. Ledyard Stebbins student grant program, established in celebration of his 90th birthday.
Key publications
- Variation and Evolution in Plants (1950)
- Processes of Organic Evolution
- The Basis of Progressive Evolution (1969)
- Chromosomal Evolution in Higher Plants (1971)
- [[Flowering Plants: Evolution Above the Species Level]] (1974)
- Evolution (1977) with Dobzhansky, Ayala and Valentine
- Darwin to DNA, Molecules to Humanity (1982)
References
Cited references
- ↑ Yoon C. K. January 21 2000. Ledyard Stebbins, 94, Dies; Applied Evolution to Plants. New York Times, Section B, Page 9
- ↑ Gustafsson, Å. 1946–1947. Apomixis in higher plants. C. W. K. Gleerup, Lund.
- ↑ Stebbins, G. L., Jr. 1940. The significance of polyploidy in plant evolution. The American Naturalist LXXIV:54-66
- ↑ Stebbins, G. L. 1985. Polyploidy, Hybridization, and the Invasion of New Habitats. Annals of the Missouri Botanical Garden 72:824-832
- ↑ Faber, P. M. 2000. [G. Ledyard Stebbins Jr. 1906 - 2000]. Fremontia 28:69-70
- ↑ Smocovitis, V. B. 2001.[G. Ledyard Stebbins and the evolutionary synthesis]. Annual Review of Genetics 35:803-814
- ↑ Wright, S. January 28 2000. [Pioneer biologist Stebbins dies]. Dateline UC Davis
- ↑ Smocovitis, V. B. 1999. Living with Your Biographical Subject: Special Problems of Distance, Privacy and Trust in the Biography of G. Ledyard Stebbins Jr. Journal of the History of Biology 32:421–438
General references
- Mayr, E. 2002. [G. Ledyard Stebbins]. Proceedings of the American Philosophical Society 146:129-131
- Raven, P. H. 2000. [G. Ledyard Stebbins (1906–2000): An appreciation]. Proceedings of the National Academy of Sciences 97:6945-6946
- Smocovitis, V. B. 1997. G. [Ledyard Stebbins, Jr. and the evolutionary synthesis (1924 - 1950)]. American Journal of Botany 84:1625-1637
- Smocovitis, V. B. and Ayala, F. J. 2000. [George Ledyard Stebbins]. ''Biographical Memoirs of the National Academy of Sciences 85:290-313
External links
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