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CHARLES GALD SIBLEY August 7, 1917-April 12, 1998 BY ALAN H. BRUSH CHARLES GALD SIBLEY WAS born in Fresno, California, on August 7, 1917, en cl cliecl at age 80 in Santa Rosa, Cali- fornia. He was not a small-town boy who simply movecl upstate. Between his early years in Fresno en c! his ultimate move to Santa Rosa, Charles travelecl worIc~w~cle to conduct en cl report on his research. He was one of the leacling ornithologists cluring the latter half of the twentieth century, one of the founders and a major player in the emerging fielcl of molecular systematics, en cl contributed significantly to our knowledge of the evolutionary relationships among the higher avian taxa. CharIes's intellectual intensity en cl excitement touched the lives of many of his contemporaries in ways both good en cl bacI, en cl he influenced several generations of students. Few ornithologists have so polarizecl their students en cl colleagues. Ultimately his greatest impact may be the trans- mission of his icleas en cl intellectual fervor to students, which he clicl with an evangelical intensity, sometimes threatening his wrath but usually with the grace of a master communicator. Charles was an exceptionally well-organized person, blessed with a fine intellect and an unyielding belief in himself. Those at the receiving ens! of one of his famous 217
218 B I O G RA P H I C A L EMOIRS verbal debates or attacks may not have Tookoc! beyonc! their own bruised egos to appreciate his finer qualities. He was a generous person, giving freely and frequently of his time to students en c! colleagues, particularly if it involves! cliscus- sions of science. He took pricle in his broacl unclerstancling of biology en cl its processes, but he stuck to his own beliefs en c! unclerstancling of biological "facts" until presenter! with unequivocal information that he was wrong. Then, immecli- ately, he wouIcl champion the new information, never looking back to c~well on the fact that he may have been wrong. This contrary nature of being dogmatic on the one hancI, while always welcoming new information on the other, macle it clifficult for some people to clear with Charles en c! his science, but for his students he was an encIlessly variable, fascinating, en cl challenging role moclel. Charles was associates! with six universities over the course of his academic career. His first appointment was a one- year assistant professorship in 1948 at the University of Kansas. A year later he returnee! to his native state to join the faculty of San lose State College (now California State University at San loser as an assistant professor of zoology. In 1953 he went to Cornell University as curator of bircis en c! associate professor of zoology in the Department of Conservation. During his 12 years there Charles acivancecl to professor, taught ornithology to overflowing classes of both graduate en cl unclergracluate students, clevelopecl Cornell's scientific collection of bircl specimens, en cl mentorecl nine graduate students and one postdoctoral fellow. In 1959-60 he took a sabbatical year at Oxford University as a Guggenheim fellow. Back on the Cornell campus cluring the summer of 1962, he oversaw the activities of the 13th International Ornitho- logical Congress. Broadly speaking, his research during the Cornell years clealt with hybridization between species-pairs en c! the molecular systematics of avian orders en c! families.
CHARLE S GALD SIBLEY 219 Charles, who priclec! himself as an ornithologist, joiner! the American Ornithologists' Union (AOU) in 1939, became an electecl member in ~ 949, en cl a fellow in ~ 955. He served as treasurer for I! years, from 1953 to 1963, en c! as presi- clent cluring the 1986-~S term. Before becoming president Charles served twice as vice-presiclent en cl was electecl to several terms on the Council. In 1971 he was awarclec! the Brewster Memorial Mecial by the AOU, en cl in 1986 both he en cl his wife, Frances, became patrons of the organization he hac! server! so often en c! well. In aciclition to his AOU activities Charles was a secretary of the Cooper Ornithological Society, a fellow or corre- sponcling fellow of six foreign societies, en c! an officer or council member of five societies. From 1958 to 1962 he served as the secretary-general of the ~ 3th International Ornithological Congress, en c! from 1986 to 1990 he was president of the 20th International Ornithological Congress. Altogether he was a member of about 15 scientific societies, inclucling all major ornithological societies of the Uniter! States, as well as Deutsche Ornithologen-GeselIschaft, Societe Ornithologique cle France, Asociacion Ornitolog~ca clef Plata, en c! Suomen Lintutieteellinen ~clistys. He server! on the eclitorial boards of Evolution, Journal of Molecular Evolu- tion, en cl Molecular Biology en c! Evolution In 1965 Charles mover! to Yale University as a professor of biology, the William Robertson Coe Professor of Orni- thology, en cl curator of bircis of the Peabody Museum of Natural History. In 1970 he was appointee! director of the Peabody Museum of Natural History. During his years at Yale Charles advised another seven graduate students and three postdoctoral fellows. In 1986 he was elected to the National Academy of Sciences. That same year Charles retired and was named a professor emeritus of Yale University. Later that year he ant! Fran again mover! back to California. There
220 B I O G RA P H I C A L EMOIRS he became affiliates! with San Francisco State University as a Dean's Professor of Science en cl Professor of Biology. In 1988 Charles en cl colleague {on E. Ah~quist received the Daniel Girauc! Elliot Mecial from the National Academy of Sciences in recognition of their contributions to our knowI- ecige of avian systematics, en cl in 1991 Charles was awarclecl the ATessanciro Ghigi Mecial by the National Institute of Wildlife Biology (Italy). His final appointment occurred in March 1993 after moving to Santa Rosa. There he was namecl adjunct professor of biology at Sonoma State University, in part so that he couIcl have continual access to his extensive personal library that he hacl given to the university. In his conversations with students en c! colleagues Charles couIcl generate great excitement about the potential of his research. He clelightecl in invitations as plenary or keynote speaker ant! he occasionally organizer! mini-symposia at scientific meetings, where he en cl his students wouIcl give papers upciating their current research. Throughout his career he attracted! inclivicluals upon whose lives he macle an inclelible mark. Among those who stucliecl with him are four AOU elective members, eight AOU fellows, an AOU secretary, an editor of The Auk, en c! an AOU treasurer. Every project that Charles undertook clemonstratecl his talent for enlisting the help of an extraordinary diversity of people en c! expertise. For example, in 1961 when he first conceived of a DNA hybridization facility at Cornell, he sent K. W. Corbin to Bethesda to learn the techniques from the three investigators who hac! only months earlier clevel- opecl the methoclology. In 1966 when Sibley wan tell avian bloocl samples from European species, he contacted a num- ber of friencis who wouic! be at that year's International Ornithological Congress in Oxford, asking for their aicl in that early work on hemoglobin, Charles was never hesitant
CHARLE S GALD SIBLEY 221 to enlist knowlecigeable inclivicluals well outsicle academia in order to achieve his goals in fieldwork. No fieldwork of his illustrates this better than the immense effort he put into planning for the 1969 National Science Foundation expedition to Papua-New Guinea aboard the research vessel Alpha Helix. A year prior to that expedition Sibley en c! Prof. George A. Bartholomew (of the University of California, Los Angeles) macle a comprehensive assess- ment of the potential fielcl facilities, logistics, en cl personal contacts in that vast region. There they enlister! the coop- eration en cl help of an amazing group of inclivicluals, some of whom were local officials, administrators, ministers of either the Lutheran or Catholic churches, an archbishop, ranchers, pilots, local scientists en cl educators associated with the Australian National University facilities, members of the Australian Bush Patrol, telegraph operators, directors of sanctuaries, en cl native Papua-New Guineans. As a youngster Charles was an avicl bircler en cl kept precise records of his observations very early on. He was introclucec! to natural history by reacting John Burroughs en cl Ernest Thompson Seton. Close friend Robert Failing encouraged his interest in bircis, en c! high-school teacher Jean M. Nelson was particularly supportive of his interests in natural history. Together they founded the natural sciences club at Oakland High School. In the mic! 1930s as an unclergracluate at the University of California, Berkeley, he gravitated to the Museum of Vertebrate Zoology (MVZ). MVZ hacl become a major center for the stucly of natural history uncler the direction of Joseph Grinnell, whose fielcl notebook methods Charles wouIcl later use to fill 15 volumes that cletailecl years of fieldwork in his precise, uneclitec! script. The MVZ main- tainecl an emphasis on the fauna of the region, as well as an association with the museum of paleontology. Accordingly,
222 B I O G RA P H I C A L EMOIRS his first publications were on fossil bircis obtainer! from the tar pits at Rancho La Brea in Los Angeles. After graduation from Berkeley in 1940 (A.B. in zoology), Charles worker! one year for the U.S. Public Health Service on plague suppressive measures. Military service intervened, en cl he was commissioned as an ensign in the U.S. Navy reserves. During the later stages of Woric! War II he was callecl for active duty en cl rose to lieutenant as a communi- cations officer in the Pacific theater cluring the last 19 months of the war. His primary station was on Emiru IsTanc! in the St. Matthias group, 75 miles off the northern tip of the Bismarck Archipelago. During his off-duty time he collectecl locally en c! sent scientific specimens back to the MVZ. That effort on Emiru was supplementecl while on rest-ancI- relaxation expeditions to the Solomon Islancis and the Philippines. This combination of travel en cl the collection of scien- tific specimens was pure pleasure for Charles en cl wouIcl typify family travel experiences over his lifetime. As the years passed, his collection of museum specimens was replacecl by the collection of egg-white en cl bloocl samples for serum, hemoglobin, en c! ultimately the extraction of DNA. For example, following the ~ 4th International Ornithological Congress in Oxford, England, Charles organized a month- Tong European vacation arounc! visits to zoological gardens, aviaries, and the homes of European colleagues in an ongoing effort to obtain critical species for his research. After the war en c! now married, Charles returnee! to Berkeley in 1946 to pursue a cloctoral degree uncler the direction of Alclen H. Miller, who was himself a protege of Joseph Grinnell. By the micI-1 940s Miller hac! follower! Grinnell into the directorship of the MVZ en cl was particu- larly interested in species-level taxonomic problems. At that time Charles met John Davis, another incoming Miller cloc-
CHARLE S GALD SIBLEY 223 toral student, whom he joiner! on a series of collecting trips to Mexico. As a result Charles became fluent in Spanish, Earned the ropes of carrying out fieldwork in Mexico, en cl was introclucec! to some peculiar Mexican birc! specimens collectecl by Helmuth Wagner. Those specimens turned out to be hybrids between two species of towhee in the genus Pipi~o. Subsequently, for his cloctoral research Charles cleciclecl to examine the complex patterns of plumage variation causecl by hybridization en cl the breakdown of species-specific reproductive isolating mechanisms between the recI-eyocl towhee, P. erythrophthalmus, en cl the colIarecl towhee, P. ocai, along the transvoIcanic plateau of Mexico. This was a zone of hybridization that stretched nearly 500 miles from southeastern {alisco to the states of Veracruz en cl Puebla. His thesis "Species Formation in the RecI-eyoc! Towhees of Mexico" was publisher! as volume 50 of the University of California Publications in Zoology en cl was the first of 17 of his publications that clealt with avian hybridization. A major contribution of his doctoral work was the appli- cation of a method for summarizing the plumage variation among hybridizing inclivicluals as a single number, a hybric! inclex value. The establishment of a species-specific hybrid inclex scale was an extraorclinarily powerful en cl ingenious method for analyzing complex, multigenic traits whose mor- phological patterns shifted geographically due to hybridiza- tion between incipient species. The method was later usecl by his first group of graduate students to study the complex patterns of hybridization between species-pairs in the Great Plains of North America. In retrospect, CharIes's cloctoral research can best be clescribec! as an early descriptive stage in the clevelopment of his unclerstancling of the role playocl by hybridization, both during the process of speciation and as a result of the breakdown of reproductive isolating mecha-
224 B I O G RA P H I C A L EMOIRS nisms. These were significant conceptual en c! methoclological contributions to our unclerstancling of hybridization as a mechanism of evolution. After Sibley mover! to Cornell University the hybricliza- tion studies were extenclecl to inclucle other species-pairs that hybriclizecl throughout the Great Plains of North America. They incluclec! Bullock's en c! Baltimore orioles, yellow-shaftec! en cl recI-shaftecl flickers, indigo en cl lazuli buntings, en cl rose-breastecl en cl black-heaclecl grosbeaks. Those years were heacly, exciting times for him, involving his first graduate students, Davicl A. West, Lester L. Short, Frecl C. Sibley (unrelatecI), en cl Paul A. {ohnsgarcl in many fielcl trips to collect hybrids along the Platte River en c! elsewhere in Colo- raclo, Kansas, Nebraska, en cl the Dakotas. In aciclition he revisited the Mexican highIancis to extend his earlier work there. Although the hybrid inclex method hacl proven to be a powerful tool for studying the complexities of hybricliza- tion for the breakdown of reproductive isolation, by 1958 Charles was looking for better ways to quantify the degree of introgression between species-pairs. Simultaneously Paul Johnsgarc! was in neec! of financial support to complete his own cloctoral thesis. In an attempt to resolve both issues Charles wrote a small proposal to the National Science Foun- ciation to examine the possibility of using the new technique of paper electrophoresis to study species-specific variation in the serum proteins of game bircis. If successful, it might be applied to the analysis of genetic variation in hybrid populations. As the research assistant in this small study {ohnsgarcl followed Charies's instructions to the nth degree almost. It was the "almost" that wouIcl prove to be serendipitous. Like most of CharIes's students both then en cl subsequently, Paul stood in mortal fear of invoking his wrath. Departure
CHARLE S GALD SIBLEY 225 from the laboratory protocols was a carclinal sin. Paul, how- ever, hacl react McCabe en cl Deutsch's earlier paper on the electrophoresis of egg-white proteins. Out of curiosity en cl a broacler interest, but without Charies's consent, Paul incluclecl a few egg-white samples along with the serum samples cluring his electrophoretic analyses. At it turner! out, even with the crucle technique of paper electrophoresis, the serum protein electrophoretic patterns seemed much too variable among inclivicluals to be appliecl to the hybridization studies. (Recall that at that time nothing was known about protein variation, either within or between species.) Lamenting this en cl greatly cliscouragecI, Charles began to write up the results as a report to the National Science Foundation. It was then that Paul mustered the courage to reveal his covert analyses. The egg-white electro- phoretic patterns were consistent among inclivicluals of a species en cl clifferecl among the few species that hacl been examined. Charles instantly recognized the implications of those observations. A powerful new too! en c! a new set of characters were awaiting application by systematists. Almost overnight he put aside his plans for using serum proteins to study the variation among hybrids and began to lay plans for an electrophoretic study of egg-white protein variation in bircis. Over the subsequent clecacle en cl a half that research wouic! become a massive comparative taxonomic stucly of the higher avian taxa. IncleecI, the relationships among avian orders en cl families wouIcl be at the forefront of his research interests for the remainder of his life. Thus began the next phase of CharIes's research, which wouIcl overshadow the earlier work throughout the 1960s en cl into the early 1970s. The move to electrophoretic analyses of egg-white pro- teins involvecl a major shift in CharIes's career. Along with Herb Dessauer of Louisiana State University, who stucliecl reptiles en c! amphibians, en c! Morris Goodman of Wayne
226 B I O G RA P H I C A L EMOIRS State University, who stucliec! primates, Charles became one of the founders of molecular systematics. For each of these men this shift required a great clear of retooling both men- tally en c! in the laboratory. The transition involves! a move from activities that primarily usecl classic fieldwork couplecl with comparative morphology to one of ciaily laboratory analyses using the methods of comparative biochemistry. As one might expect, the new approach was also encumbered with some of the oIcl thinking. A peculiar bias that Charles carrier! concerned! the genetic variation of structural proteins versus enzymes en cl the ways that natural selection wouIcl constrain the latter. He, along with one of his colleagues at Cornell, believer! that enzymes wouIcl be invariant in their amino acid sequences clue to evolutionary constraints on their activity. Enzymes, in their view, functioned only at specific temperatures and pH values, en cl natural selection wouIcl weecl out all but the most ef- fective structure for each enzyme en cl species. IncleecI, clur- ing the early 1960s Charles en c! his colleague believer! that an enzyme's primary structure might prove to be iclentical both within and among species. Any variation in an enzyme's structure wouic! rencler it inactive according to their logic, en cl they knew little about the newly cliscoverecl phenomenon of allozymes being stucliecl by AlIan C. Wilson at the University of California, Berkeley, en c! Clement C. Markert at Johns Hopkins University. Thus, in their view enzymes wouIcl be unlikely to carry phylogenetic information en cl wouIcl be useless for both systematic en c! population genetic studies. Throughout much of the 1960s, informal debates on this issue occurred between Charles en cl Wilson. WiTson's careful studies of allozyme variation, coupled with Markert's research on picine lactate clehycirogenases, eventually convinced Charles that enzymes clicl in fact vary within species. This conversion proviclec! the basis for another
CHARLE S GALD SIBLEY 227 attempt to stucly the hybrids of the Great Plains. Though the shift in research was tangential to his main interests, it began in 1969 during the Alpha Helix expedition to Papua- New Guinea, where the laboratory work took place aboarc! the ship. Though the primary thrust of that expedition was to be a general sampling of the fauna of the worIcl's second largest isTancI, Charies's team also carrier! out some popula- tion genetic studies. Among other research problems, these incluclecl both hybridizing species-pairs birds of paradise of the genus Paraclisaea) en c! non-hybriclizing species com- plexes (starlings of the genus Aplonis). In fact, of the 22 members of that expedition, 9 subsequently focused their activities on different studies of allozyme variation within en cl among populations. In aciclition to Charles, who was the prime mover and organizer of the expedition, the molecular systematists were H. C. Dessauer, A. C. Wilson, K. W. Corbin, A. H. Brush, A. Ferguson, I. E. Ah~quist, R. Storez, en cl V. M. Sarich. From the outset of that work Charles was impresser! by the analytical results involving two classes of enzymes, the esterases en cl the clehycirogenases. Both were variable within en c! among populations, en c! the frequencies of their vari- ants (i.e., alleles) couIcl be usecl to characterize incliviclual populations. Within a few weeks of seeing the first electro- phoretic results aboarc! the Alpha Helix, Charles began to think about applying the new methods to the hybrids of the Great Plains. The approach wouIcl be to sample popula- tions of hybridizing species-pairs at intervals across the hybrid zone, just as in the earlier studies of plumage variation. This time, however, in aciclition to the construction of hybrid inclexes, polymorphic enzymes, esterases perhaps, wouic! be analyze cl for their variation by means of electrophoresis. In contrast to the introgression of complex multigenic traits as quantifier! by hybric! inclexes, the electrophoretic studies
228 -a- B I O G RA P H I C A L EMOIRS of gene flow would involve single gene traits with simple patterns of inheritance. The following year those plans began to unfold. The research vessel would be a modern prairie schooner, an Airstream trailer, outfitted with all essential electrophoretic equipment. A full crew was put in the field. After the first week the collecting focused on orioles and a study of the introgression of genetic variation caused by hybridization between the Bullock's and Baltimore orioles. The results flowed in. Specimens were collected in the mornings and late afternoons, during the midday periods enzymes were extracted and analyzed by means of starch gel electrophoresis. in. . . . · 1 he Database mounted and soon became impressive, en- couraging the collecting party westward in 50-mile leaps across the zone of hybridization, and then back eastward, filling in the gaps between the initial collecting localities. The collecting continued in 1971 and 1974. The results of the population genetic analyses confirmed the earlier morphological studies. Gene flow across the Great Plains was extensive, at least among populations of orioles. Alleles at esterase loci were being exchanged between the eastern and western populations, just as the plumage characters flowed eastward and westward through the filter of the zone of hybrids along the Platte River in Nebraska and Colo- rado. Presumably gene flow was comparable in the other riparian habitats stretching across the plains, although CharIes's studies of the patterns of hybridization in the Mexican towhees showed that such assumptions might be unwarranted. Nevertheless, these studies and those by others revealed that the species of these hybridizing species-pairs might in fact be subspecies. This recognition was reflected in later versions of the AOU Checklist of North American Bircis. By 1974 Charles was already a decade and a half into
CHARLE S GALD SIBLEY 229 the taxonomic comparison of the egg-white proteins. The early electrophoretic methods for the separations of proteins on paper strips soon became obsolete. Paper electrophoresis gave way to starch gel electrophoresis, whose relatively crucle resolution potential was supplantecl by polyacrylamicle gel electrophoresis en cl eventually by isoelectric focusing in either polyacrylamicle gels or agarose plates. In an ongoing attempt to refine en cl improve his comparative ciata, Charles acloptecl each new improvement almost as soon as it became com- mercially available. Early on he was convinced that the comparative stucly of protein variation couIcl aicl significantly in determining avian phylogenetic relationships at the higher levels of classification. He was equally certain that the methods wouIcl not be much help at the levels of species en cl genera. Although protein differences were basically phenotypic characters, they clifferec! in one significant way from the traclitional morphological characters usecl by most systematists at that time. Namely, protein structure, cleterminec! by amino acic! sequences, was only one step removed from the genetic code itself. Conse- quently, differences among proteins were a more direct reflection of the unclerlying genetic similarities en c! cliffer- ences among species than was gross morphology. It was this relationship between genes en cl the traits they encoclecI, in this case the primary structure of proteins, that convincer! Charles he was on the right track. The first results of the early electrophoretic studies sug- gested that the relationships among the higher taxa might be cleterminecl with relative ease. The protocols were simple: obtain egg white from the species of interest, separate the proteins of each sample on either starch or polyacrylamicle gels uncler appropriate controls en cl stanciarcl electrophoretic conditions of wattage en cl time, stain the gels with amigo blue black, photograph the gels, and then compare the
230 B I O G RA P H I C A L EMOIRS resulting patterns. Voila! Evolutionary relationships were revealecl like never before. It was a heacly time, en cl the worIcl was watching en cl waiting for the results. Some were envious that Charles was making such headway in solving age-oIcl taxonomic problems, others were bitter that their own expertise was being eclipsecI, but most ornithologists were enthusiastic about the progress being macle. By as early as 1959 the Cornell laboratory was deeply involvecl in a comparative study of the egg-white proteins by means of acrylamicle gel electrophoresis in small glass tubes. Soon thereafter, en cl with his usual skill, energy, en cl enthusiasm, Charles was extolling the virtues of those ciata in resolving Tongstancling systematic problems. At annual scientific meetings en cl through invited lectures in North America and Europe he spreacl the message about the wonclers of the new comparative methods. In 1960 he eagerly presented ciata that clemonstratecl the affinities of the OIcl WorIcl sylviicis en cl muscicapicis in contrast to their more distant New Woric! cousins, the paruTicis. By the time of the 13th International Ornithological Congress, which was helcl in 1962 in Ithaca with Sibley as secretary-general, there were electrophoretic ciata bearing upon the relationships of many · · ~ more Ivan fame. yes. The methods of electrophoretic analysis may have been relatively uncomplicatecI, but the effort to examine the evo- lutionary relationships of all the higher avian taxa by means of electrophoresis was daunting. There were the nests of thousands of species to find. Each egg-white specimen had to be compared electrophoretically over en cl over again. Thousands of analyses were carried out over almost two decades. Nothing but unequivocal data would satisfy Charies's objectives. How else couIcl one compare all of the higher avian taxa by means of this new technology? The museums of the woric! houses! the scientific specimens neeclec! for
CHARLE S GALD SIBLEY 23 comparative morphological studies, but there were no depositories of egg-white specimens. Every species usecl in CharIes's research program hacl to be collectecl by him en cl his collaborators. Charles set out to clo that, encouraging volunteers from throughout the worIcl to collect samples en cl ship them to Cornell University. The effort was massive en c! profouncITy successful. For over a clecacle the samples came in from every continent. Willing students acquired collecting per- mits, risker! their necks climbing trees en c! cliff faces, comber! forests, prairies, en cl tundra, all in search of samples from both common en cl rare species. Hosts of both professional ornithologists en c! amateur birclers collaborates! in the effort. Along the way more than a clozen technicians carried out the lab work that was completecl at Cornell en cl Yale. The effort was monumental en c! culminates! in two monographs publishecl by the Peabody Museum of Natural History at Yale University: the first authored by Charles alone (1970) en c! the seconc! coauthored! with l. E. Ah~quist (1972~. Charles was proucl of these publications, as well he shouIcl have been. Many taxonomic problems were resolvecI, although others remained. In aciclition to the egg-white protein studies there were sicle excursions to utilize other protein systems either by way of confirmation or for specific taxonomic problems. One of these, coauthored with A. H. Brush, involvecl an extensive stucly basecl on the electrophoretic variation of eye lens proteins. Another, coauthored with H. T. Hendrickson, involved the plasma proteins. Two particularly intractable taxonomic problems, one involving the relationships of the flamingoes en c! the other the relationships of the seer! snipe, were tackled by using ion-exchange column chromatographic techniques to examine variation in the tryptic peptizes of hemoglobins. Other studies were never publishecI. The most
232 B I O G RA P H I C A L EMOIRS important of these was a massive database clevelopec! at Yale clearing with the electrophoretic variation of avian hemo- gIobins Sanples were obtained from over half of the then recognizes! birc! species. Another stucly involves! the use of serology to examine the bloocl serum proteins of muscicapicis en cl sylviicis. Ultimately it was the stucly of the egg-white proteins that pair! the highest cliviclencis. The egg-white studies of the bircis of the worIcI, follow- ing those of avian hybridization on the Great Plains, wouIcl have been a life's work for most inclivicluals in academia but not for Charles. As the successes of the electrophoretic analyses of the egg-white proteins began to accumulate, a new technique was being tested in his laboratories at Cornell en cl later at Yale. The methocl's early clevelopment by others was an attempt to examine differences in DNA molecules by means of annealing, or hybridizing, short fragments of DNA to one another. The technique soon became known as DNA-DNA hybridization. Although CharIes's laboratory at Cornell began to explore the potential of the methoc! as early as 1963, another clecacle wouIcl pass before Charles hacl perfected the "DNA machine" in his laboratories at Yale. The DNA-DNA hybridization studies involves! the clevel- opment of another tissue collection. Initially, while at Cornell, an attempt was macle to use tissue culture methods to grow avian fibroblasts obtainer! from embryos. This methoc! was soon abanclonecl clue to technical problems en cl the avail- ability of a more direct method. Because bircis have nucleatecl rec! blooc! cells, blooc! samples were the obvious en c! expedient source of DNA. By the mid-1970s studies of the proteins of egg white, bloocI, en cl eye lenses were all but complete, it was time for the DNA studies to begin in earnest. The years at Yale were some of the best for Charles en cl some of his worst. The best saw the publication of his egg- white monographs by the Peabody Museum of Natural His-
CHARLE S GALD SIBLEY 233 tory en c! the clevelopment of the DNA-DNA hybridization database. By 1986 the latter was being usecl to piece together a comprehensive phylogeny of the orders en cl families of the bircis of the woricI. In printer! form the clencirogram spanned more than 20 feet along the walls of poster sessions helcl in conjunction with annual scientific meetings cluring the 1980s. It thus became known as the tapestry en c! was a phenomenon in itself, as groups of people simultaneously examined its cletails. The worst moments at Yale involves! allegations against Charles for two kinds of scientific impropriety. The first was a fecleral indictment alleging that he hacl illegally importer! the egg white of six European species, inclucling one that was wholly fictitious en cl contrived by unknown inclivicluals, either within or outside the U.S. Fish en cl WilcI- life Service. After a goof! clear of meclia attention en c! the paying of a substantial fine, this episode eventually lecl to CharIes's resignation of the directorship of the Peabody Museum of Natural History. It was a sac! moment, incleecI, for a man who hacl priclecl himself for following the fecleral guidelines regarding the necessary scientific collecting per- mits here en c! abroad. It was simultaneously a black mark against the scientific community that clicl so little to protest this injustice. Sibley never explainecl why he chose to pay the fine uncontested. From a scientific point of view the second allegation was much more serious. It involvecl the informal charge that the analyses of DNA-DNA hybridization ciata hac! been manipulatecl to yielcl results that conformed with precon- ceivecl notions of phylogenetic relationships. One couIcl argue that the methods of ciata analysis were not as rigorous as they might have been. There were certainly differences of opinion among the members of Sibley's own research group on how best to quantify and summarize the data, however,
234 B I O G RA P H I C A L EMOIRS this was an aspect of natural growth en c! clic! not constitute fraud. In fact, the issue probably wouIcl never have arisen if Charles en cl his group hacl not ventured into the treacher- ous waters involving human evolution. The debates in that arena are legenciary, beginning with Raymond Dart en cl leacling up to tociay's antagonists. In Sibley's case the issue revolver! arounc! rates of genetic change along different phylogenetic lineages: specifically, the one that led to the genus Homo, the other leacling to the remaining higher primates. It was this debate that focuses! the attention of the scientific community on CharIes's preferred methods of analysis of the DNA hybridization ciata. At its heart the issue was whether the entire genome of an organism evolves! at a constant average rate, as Charles maintained. Although there is solicl evidence to suggest that rates of change clo cliffer among different lineages, the issue is still unresolvecI. As in all other matters of his life Charles believecl in himself. He believed unequivocally that his analyses of the relationships of the bircis of the woric! were correct. In 1990 Yale University Press publishecl two massive scientific con- tributions. One, in collaboration with his close friend en cl colleague Burt Monroe, Jr., was Distribution en c! Taxonomy of the Bircis of the Worm, a comprehensive treatment of all avian species recognized as of ~ 990. The other, with his longtime associate Jon E. Ah~quist, was Phylogeny en c! C]assi- fication of the Bircis of the Worm: A Stucly in Molecular Evolution This was the tapestry, along with all of the support- ing data. Charles knew the history of systematics well. He knew better than most that classifications were always uncler review ant! mollification, ant! he clic! not cleTucle himself into believing that his classification wouIcl be the final worcl on avian taxonomy. One of his cireams, however, cluring the early phase of the DNA research was to be able to react off
CHARLE S GALD SIBLEY 235 nucleoticle sequences from a DNA molecule. That was the kind of precision he sought, knowing full well that the tech- nology of the 1970s en cl 1980s was not up to that task. Today automatic DNA-sequencing methods produce Tong sequences of nucleoticles, en cl several genome projects are at or nearing completion. AIreacly his students en cl their students have built upon the contributions macle by Sibley en cl his group. The possibility of eventually reaching a con- sensus with regard to the phylogenetic relationships of bircis is certainly obtainable, something that wouic! give Sibley immense satisfaction. Charles passed away at his home in Santa Rosa on Easter Sunday, April 12, 199S, from myelogenous leukemia. He is survival by Frances, his wife of 56 years, whom he met as Frances Louise Kelly, en cl their daughters, Barbara Susanne, Dorothy Ellen, en c! Carol Nacline. THE TEXT OF THIS biographical memoir was modified from one pub- lished in The Auk (116~19993:806-14), coauthored by Kendell C. Corbin and Alan H. Brush. I thank both Corbin and Jon Ahlquist for their contributions.
236 B I O G RA P H I C A L EMOIRS SELECTED BIBLIOGRAPHY 1939 Fossil fringillids from Rancho La Brea. Condor 41:126-27. 1950 Species formation in the red-eyed towhees of Mexico. Univ. Calif Publ. Zool. 50:109-94. 1954 Subspecies and clines: The contribution of avian taxonomy. Syst. Zool. 3:105-10. 1955 Hybridization in the red-eyed towhees of Mexico. Evolution 8:252-90. Ornithology. In A Century of Progress in the Natural Sciences 1853- 1953, pp. 620-59. San Francisco: California Academy of Sciences. 1957 The evolutionary and taxonomic significance of sexual dimorphism and hybridization in birds. Condor59:166-91. 1958 With D. A. West. Hybridization in the red-eyed towhees of Mexico: The eastern plateau populations. Condor 60:85-104. 1959 With P. A. Johnsgard. Variability in the electrophoretic patterns of avian serum proteins. Condor 61 :85-95. 1960 The electrophoretic patterns of avian egg-white proteins as taxo- nomic characters. Ibis 102:215-84. 1962 The comparative morphology of protein molecules as data for classif~ca- tion. Syst. Zool. 11:108-18.
CHARLE S GALD SIBLEY 1968 237 With K. W. Corbin and J. E. Ahlquist. The relationships of the seed- snipe (Thincoridae) as indicated by their egg-white proteins and hemoglobin. Bonn. Zool. Beitage 19:235-48. 1970 A comparative study of the egg-white proteins of passerine birds. Bull. Peabody Mus. Nat. Hist. 32:1-131. 1972 With J. E. Ahlquist. A comparative study of the egg-white proteins of non-passerine birds. Bull. Peabody Mus. Nat. Hist. 39:1-276. 1973 With J. E. Ahlquist. The relationships of the hoatzin (Opisthocomus). Auk 90:1-13. 1974 With K. W. Corbin, A. Ferguson, A. C. Wilson, A. H. Brush, and J. E. Ahlquist. Genetic polymorphism in New Guinea starlings of the genus Aplonis. Condor 76:307-18. 1980 With J. E. Ahlquist. The relationships of the "primitive insect eaters" (Ayes: Passeriformes) as indicated by DNA-DNA hybridization. In Proceedings of the 17th International Ornithological Congress (BerlinJ, ed. R. Nohring, pp. 1215-20. Berlin: Deutschen Ornithologen- Gesellschaf. 1983 With J. E. Ahlquist. The phylogeny and classification of birds based on the data of DNA-DNA hybridization. Curr. Ornithol. 1:245-92. 1984 With J. E. Ahlquist. The phylogeny of the hominoid primates, as indicated by DNA-DNA hybridization. 7. Mol. Evol. 20:2-15.
238 B I O G RA P H I C A L 1985 EMOIRS With J. E. Ahlquist. The phylogeny and classification of the Australo- Papuan passerine birds. Emu 85:1-14. 1986 With J. E. Ahlquist. Reconstructing bird phylogeny by comparing DNA's. Sci. Am. 254:82-92. 1987 With J. E. Ahlquist, A. H. Bledsoe, and F. H. Shelton. DNA hybrid- ization and avian systematics. Auk 104:556-63. With J. E. Ahlquist. DNA hybridization evidence of hominoid phylogeny: Results from an expanded data set. 7. Mol. Evol. 26:99-121. 1988 With J. E. Ahlquist and B. L. Monroe, Jr. A classification of the living birds of the world based on DNA-DNA hybridization studies. Auk 105:409-23. 1990 With J. A. Comstock and J. E. Ahlquist. DNA hybridization evidence of hominoid phylogeny: A reanalysis of the data. J. Mol. Evol. 30:202-36. With J. E. Ahlquist. Phylogeny and Classification of the Birds of the World: A Study in Molecular Evolution. New Haven: Yale University Press. With B. L. Monroe, Jr. Distribution and Taxonomy of the Birds of the World. New Haven: Yale University Press. 1994 With J. C. Avise and W. S. Nelson. DNA sequence support for a close phylogenetic relationship between some storks and New World vultures. Proc. Natl. Acad. Sci. U. S. A. 91:9861-65.
