Biogeography, Changing Climates, and Niche Evolution
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FROM THE ACADEMY: COLLOQUIUM PERSPECTIVE Biogeography, changing climates, and niche evolution David B. Wakea,b,1, Elizabeth A. Hadlyc, and David D. Ackerlya,d aDepartment of Integrative Biology, bMuseum of Vertebrate Zoology, and dJepson Herbarium, University of California, Berkeley, CA 94720; and cDepartment of Biology, Stanford University, Stanford, CA 94305 Edited by James Hemphill Brown, University of New Mexico, Albuquerque, NM, and approved September 29, 2009 (received for review September 25, 2009) odern concepts central to future will have access to the original figure in the history of science who current studies of biogeog- record of faunal conditions in Cali- wrote extensively about the relationships raphy, changing climates fornia and the west wherever we now of climate and vegetation. As a result of and evolution of ecological work. his studies of Volca´n Chimborazo in Mniches were born approximately a hun- Ecuador, von Humboldt appears to have These ideas were prophetic, and have dred years ago. In 1908, the Regents of been the first well known scientist to a special poignancy at this time, when the University of California established discuss the zonation of vegetation along the impact of global climate change is the Museum of Vertebrate Zoology at an altitudinal transect and to develop a evident and when we realize how much Berkeley, in accordance with the wishes concept of life zones (4). von Hum- we rely on records from the past, such of Annie M. Alexander (1867–1950). boldt’s work deeply influenced C. Hart as those meticulously kept by Grinnell, Alexander conceived the institution and Merriam who recalled, shortly before his his students, coworkers and successors. selected its first Director, Joseph Grin- death, his father handing him a volume A century has now elapsed since the nell (1877–1939), a well known natural- of Humboldt’s ‘‘Views of Nature’’, Museum was founded, and we were ist who had received his Ph.D. at Stan- where he found early inspiration for his stimulated by Joseph Grinnell’s words to ford University and was then teaching at work on species distributions (5). Merri- take stock of our current understandings the Throop Institute in Pasadena (later am’s classic study of the San Francisco of the relationships between geography, the California Institute of Technology). Mountains in Northern Arizona and his Grinnell, who founded the Museum in climate, and the distribution and ecolog- ical niche dimensions of organisms in an biological survey of Mt. Shasta led to late 1908, meticulously adhered to the the development of his highly influential principles laid down by Alexander (1). ecological and evolutionary context, us- ing modern methods and approaches. life zone concept (6). Merriam recog- Alexander would provide the funding nized 12 life zones in the United States and inspiration and Grinnell would do In this issue contributions are pre- sented from an Arthur M. Sackler Col- and mapped them, noting that on altitu- the intellectual and practical work to dinal transects (e.g., from the Sonoran establish the institution and set it on a loquium of the National Academy of Sciences, held in Irvine, CA, December Desert to Humphrey’s Peak) one would trajectory. The Museum quickly became pass through as many as six life zones. known for its studies of terrestrial verte- 11–13, 2008, in celebration of the Cen- tennial of the Museum of Vertebrate Groups of species of plants and verte- brates, conducted in the framework of brates were associated with each zone, what we would recognize today as ecol- Zoology at the University of California at Berkeley and with the spirit of Grin- and thus the zone itself became predic- ogy and evolution. The founders were tive. Grinnell was strongly influenced by self-conscious of their roles from the nell’s contributions in mind. The collo- quium was focused on issues central to this approach, and it became a hallmark beginning. They had no illusions that of his subsequent research, especially the work they set out to do would be Grinnell and his colleagues one hundred years ago: biogeography, niche evolution evident in his famous studies of Yo- easy or soon accomplished, if ever. semite National Park (7), and through- Grinnell (2) set the course: and changing climates (or, more gener- ally, environments, for Grinnell focused out his life he made regular emenda- It will be observed, then, that our much attention on human-induced im- tions to his life zone map of California. efforts are not merely to accumulate pacts on the California environment). Although life zones became increasingly as great a mass of animal remains as Grinnell was a pioneer in studying geo- controversial through time, attempts to possible. On the contrary, we are graphic variation within and between adapt the life zone approach to modern expending even more time than species, in focusing on the relationships understandings were made by several would be required for the collection between geography, ecology and the authors, notably Holdridge (8). Hold- of the specimens alone, in rendering distribution of organisms, and especially ridge’s life zones, based on integration what we do obtain as permanently in the formulation of the ecological of biotemperatures, precipitation, and valuable as we know how, to the niche concept (3). These are all current potential evapotransporation, were used ecologist as well as the systematist. It issues in modern science, and recent by many researchers, especially in the is quite probable that the facts of years have witnessed the emergence of distribution, life history, and eco- new scientific challenges, conceptual This paper serves as an introduction to the Arthur M. Sackler nomic status may finally prove to be frameworks, and analytic techniques, Colloquium of the National Academy of Sciences, ‘‘Bioge- of more far-reaching value, than what- all of which were on display at the ography, Changing Climates, and Niche Evolution’’ held ever information is obtainable exclu- colloquium. December 11–13, 2008, at the Arnold and Mabel Beckman sively from the specimens themselves. The colloquium took place at a propi- Center of the National Academies of Sciences and Engineer- ing in Irvine, CA. The complete program and audio files of At this point I wish to emphasize tious time, celebrating both the centen- most presentations are available on the NAS web site at what I believe will ultimately prove nial of the Museum of Vertebrate Zool- www.nasonline.org/SacklerBiogeography. to be the greatest value of our mu- ogy and the sesquicentennial of the Author contributions: D.B.W., E.A.H., and D.D.A. wrote the seum. This value will not, however, publication of Darwin’s Origin of Spe- paper. be realized until the lapse of many cies on November 24, 1859 (Table 1). The authors declare no conflict of interest. years, possibly a century, assuming Moreover, 2009 is also the 150th anni- This article is a PNAS Direct Submission. that our material is safely preserved. versary of the death of Alexander von 1To whom correspondence should be addressed. E-mail: And this is that the student of the Humboldt (1769–1859), a monumental [email protected]. www.pnas.org͞cgi͞doi͞10.1073͞pnas.0911097106 PNAS ͉ November 17, 2009 ͉ vol. 106 ͉ suppl. 2 ͉ 19631–19636 Downloaded by guest on September 24, 2021 Table 1. Early milestones and anniversaries related to the history of the niche concept marized the similarities and differences in biogeography, ecology, and evolution between the conceptualizations. Elton Year Milestone wanted to develop a coherent account of dynamics of interactions in communi- 1805 First publication of von Humboldt’s Volcan Chimborazo vegetation figure ties, such as food chains, cycles of abun- 1859 May 6: Death of Alexander von Humboldt (1769–1859) dance, and the like; he was less con- Nov. 24: Publication of Darwin’s Origin of Species cerned with individual species than was 1908 Founding of UC Museum of Vertebrate Zoology (Grinnell and Alexander) Grinnell. Grinnell’s niche was seen as 1910 First published use of ЉnicheЉ in ecological context (11) more habitat-oriented than Elton’s, 1917 Publication of Grinnell’s ЉThe niche-relationships of the California thrasherЉ which was seen as more function-ori- 1927 Publication of Elton’s ЉAnimal EcologyЉ ented, but both saw the niche as a place 1936 Publication of Gause’s ЉThe Struggle for ExistenceЉ or role that a species occupies in the 1944 Publication of Simpson’s ЉTempo and Mode in EvolutionЉ environment rather than as a property 1957 Publication of G.E. Hutchinson’s ЉConcluding RemarksЉ of the species itself, a view more associ- ated with Hutchinson (ref. 20; see also refs. 21 and 22). The main difference New World tropics and life zone maps Some insight into this conjecture is between Grinnell and Elton identified were produced for several countries derived from the field notes of Grin- by Griesemer is the issue of whether (e.g., refs. 9 and 10). nell’s graduate student Walter P. Taylor, more than one species can occupy a In parallel with his work on life zones, who was conducting field research in the niche, the difference stemming ulti- Grinnell pioneered the analysis of indi- Yosemite region in early December, mately from Grinnell’s systematic per- vidual species distributions in relation to 1914 (notes on file, Museum of Verte- spective and Elton’s more functional their biotic and abiotic requirements in brate Zoology, University of California, one. In a concise and forceful overview, Udvardy (23) argued that there was no his 1917 article ‘‘The niche-relationships Berkeley, CA). Following routine obser- essential difference between Grinnell of the California thrasher’’ (3). Al- vations for December 11, 1914, Taylor and Elton in conceptualizing the niche, though the term ‘‘niche’’ had previously wrote a separate section headed ‘‘The but that Grinnell’s formulation was ear- appeared in print in its ecological con- Ecological Niche.’’ These are musings, lier and broader.