What Does It Mean to Be a Naturalist at the End of the Twentieth Century? Author(S): Peter R

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What Does It Mean to Be a Naturalist at the End of the Twentieth Century? Author(s): Peter R. Grant Source: The American Naturalist, Vol. 155, No. 1 (January 2000), pp. 1-12 Published by: The University of Chicago Press for The American Society of Naturalists Stable URL: http://www.jstor.org/stable/10.1086/303304 . Accessed: 26/02/2015 12:48

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What Does It Mean to Be a Naturalist at the End of the Twentieth Century?*

Peter R. Grant†

Department of Ecology and Evolutionary Biology, Princeton published last year (1998), as the best source for answering University, Princeton, New Jersey 08540-1003 my question about our modern identity. The contrast between the sets of volumes provides a measure of the pro- Submitted July 13, 1999; Accepted August 31, 1999 fessional distance we have traveled in 100 years. I shall then consider some aspects of our future and how we Keywords: evolution, ecology, extinctions, models, syntheses, future. might expect to change yet further. This essay is a triptych of the naturalist: past, present, and future; history, mo- dernity, and prophecy. The first two panels are clear; the When I was asked to stand for nomination as president third is, of course, blurred and impressionistic, while being of this society, I asked what the president was expected to at the same time the most enticing. do. “Nothing, absolutely nothing,” came the answer, quickly followed by “You are very well qualified!” This was wrong on both counts. A major duty of the president is The Naturalist at the End of the Nineteenth Century to deliver an address to the society, “on your own work,” The roots of the modern naturalist go back deeply into I was told, “or anything else.” I have chosen the “anything natural history, that branch of the natural sciences orig- else” option. Under this licence I will share some thoughts inating in exploration and discovery that was practiced for about what it means to be a naturalist these days. I have centuries by natural philosophers, from before Aristotle to picked this theme because we are approaching a new cen- Alexander von Humboldt and beyond. In recent times tury as well as a new millennium (see Gould 1997, if in natural history has been defined ecologically by Bates doubt about when they begin), and this is a fine time for ([1950] 1990, p. 241) as “biological investigation at the taking stock of ourselves as well as for thinking about level of the individual organism: the study of the relations where science and society in general are heading. of organisms among themselves and with the physical en- So, what does it mean to be a naturalist? “Dis-moi ce vironment, and of their organization into populations and que tu manges: je te dirai ce que tu es” (Brillat-Savarin communities.” In 1899 the journal was subtitled “An Il- 1826, p. viii, Aphorisme IV), or, in the modern idiom, we lustrated Magazine of Natural History.” Being a magazine, are what we eat (Gabaccia 1998). If so, then as the Amer- it had editorials, much as Science and Nature do today, as ican Society of Naturalists, we are what we publish, because well as scientific news (scientific expeditions, recent ap- that is what we consume as readers. In this essay I shall pointments, and resignations and deaths, both here and take a look at our roots to see where we have come from abroad), and reviews of recent literature in separate sec- by first returning to the original statement of the goals of tions devoted to General Biology, Botany, Zoology, Pe- the society and then by examining the contents of volume trography, Geology, Geography, Paleontology, and An- 33 of The American Naturalist, published 100 years ago. I thropology. Its main articles were chiefly zoological and will then give the same attention to volumes 151 and 152, botanical, though occasionally anthropological or geological. It was truly, as stated, “A monthly journal devoted * This article is based on the presidential address delivered to the American to the natural sciences in their widest sense.” (The Linnean Society of Naturalists at a joint meeting with the Society for the Study of Evolution and the Society of Systematic Biologists, June 24, 1999, at the Society of London had, and still has, a similar goal.) University of Wisconsin—Madison. Intended for verbal presentation, the text Every issue of The American Naturalist carries the logo has been only slightly changed for publication. “Devoted to the Conceptual Unification of the Biological † E-mail: [email protected]. Sciences.” In 1898 this was explained in an editorial to Am. Nat. 2000. Vol. 155, pp. 1±12. ᭧ 2000 by The University of Chicago. mean the journal should counteract the tendency for nat- 0003-0147/2000/15501-0001$03.00. All rights reserved. uralists to become too specialized and to do so by pub-

This content downloaded from 128.103.149.52 on Thu, 26 Feb 2015 12:48:14 PM All use subject to JSTOR Terms and Conditions 2 The American Naturalist lishing articles on a wide variety of subjects, even at the N Ϫ 40 T=50 ϩ , risk of being thought of as “a miscellaneous lot of articles 4 which, for one reason or another, have failed to find space in the journals of the special sciences to which they rightly belong” (Bigelow 1898, p. 49). The unifying theme, Big- where T is temperature in degrees Fahrenheit and N is the elow suggested, might be “the earth and its inhabitants as number of chirps per minute given by a tree cricket, Oe- a unit. Then the problem would be to describe the various canthus niveus (Edes 1899, p. 937). parts of this unit and to explain their relations to one Naturalists did not use statistical methods of analysis another ) may it not be legitimate to adopt it as the final because such methods were not deemed to be necessary purpose of a journal which is intended to represent the or even within the naturalists’ powers to grasp and use. great body of naturalists in this country?” (Bigelow 1898, Contemporary attitudes are revealed in the review of books p. 51). on statistics. Thus wrote one reviewer: “To solve some of In fact, unification of the biological sciences was the equations, logarithms, trigonometric functions and achieved by putting everything of biological interest and gamma functions have to be employed, and it is too much some more between two covers. That is, it was a collection to hope that a large proportion of naturalists can use even rather than a synthesis. Little use was made of the Dar- these simple methods. ) Formulas are used very freely, winian paradigm as a framework for achieving unity. This which is no doubt an offense to some” (vol. 33, p. 522; is surprising in view of the importance of the Darwin- emphasis mine). The reviewer of a book on descriptive Wallace views of evolution to explorer-collector-naturalists statistics by Davenport (1899) wrote (vol. 33, p. 974), “The in the latter part of the century, such as Bates (1863), Belt gross methods already in vogue, being tolerably efficient (1874), and Wagner (1889). The 1899 volume (33) has for temporary and tentative purposes, will probably hold references to Charles Darwin on only nine pages. The “old the field for a while at least, so it will be in the remote Darwinian principle of direct benefit [of a trait] to its future when, through the plotting of curves and the use possessors” (Nutting 1899, p. 799) is referred to three of logarithmic tables, we shall see ‘by the use of quanti- times. For comparison, Wallace’s (1871) Natural Selection tative method biology ) pass from the field of speculative is discussed in only one article, in the context of adaptive sciences to that of the exact sciences.’ (p. 39).” coloration of Orthoptera. And yet sophisticated statistical analysis of data of great By and large, the naturalists 100 years ago were not a potential interest to naturalists had already begun, in a society waiting for Mendel’s laws to be rediscovered. To manner that made Mendelism desirable but not strictly varying degrees they were generalists (Mayr 1946), in- essential, and the results were also reviewed in this volume. quisitive yet skeptical, busy collecting facts about nature, Pearson’s sixth Mathematical Contribution to the Theory describing them carefully, interpreting them cautiously, of Evolution was summarized succinctly and then inter- and cataloging them systematically, yet for the most part preted as follows: “Pearson concludes: Both fertility and falling short of the goal of “scientific natural history, in fecundity are inherited, and probably in the manner pre- which,” according to Huxley (1940, p. ix), “the compar- scribed by Galton’s Law of Ancestral Heredity. ) The ative treatment of patiently accumulated data is made to importance of the demonstration of the inheritance of yield generalizations of first-class importance”: unity fertility lies in the fact that the most fertile class tends to sought in diversity. Grist to the naturalists’ mill were such form a larger and larger percentage of the whole popu- subjects as descriptions of the colors of monocotyledenous lation. Now fertility is correlated with various physical flowers; the systematics of insects, bryozoa, and hair- qualities: consequently, these physical qualities are bound worms; life histories of salamanders and lungfish; the to become predominant, if there is no interfering factor problem of explaining the significance of marine phos- at work” (vol. 33, p. 663). With a small change in focus, phorescence; how snakes feed and medusae regenerate; this would not be far off a modern statement of selection discussion of how species can be classified into four types; on fitness-related traits, with genetic correlations between and such curiosities as a chicken egg within another egg characters being one form of an “interfering factor at and a toad with five legs. Morphological and systematic work.” studies predominated and, perhaps surprisingly, field in- Thus, a biometrical branch of biology was developing vestigations played a minor role. Experiments, in the lab- that would later revolutionize the naturalists’ modus op- oratory and not in the field, were conducted to reveal erandi, but in 1899 its influence had yet to be felt. This physiological mechanisms, but description of new obser- is but one example of the curious (with hindsight) co- vations outnumbered the testing of hypotheses. Data were habitation of ancient and modern theories, ideas, and quantified but not analyzed. Volume 33 has one, empir- practices. As another example, the review of Davenport’s ically derived, equation: Statistical Methods follows a few pages after another, not

This content downloaded from 128.103.149.52 on Thu, 26 Feb 2015 12:48:14 PM All use subject to JSTOR Terms and Conditions Naturalists Past, Present, and Future 3 unsympathetic, review by Gerrould (1899) of a book on Table 1: A comparison of article subject fre- vitalism (Driesch 1899). A theory of Mesozoic landbridge quency in The American Naturalist in the years connections to Antarctica (vol. 33, pp. 975–976) and the 1899 and 1998, grouped in broad subject report of a recently accomplished transplant of the cornea categories from the eye of one rabbit to another (vol. 33, p. 62) have Topics 1998 1899 a modern ring, whereas a theory of sex, that all living Genetics: substances have two inverse and complementary types (Le Inheritance .13 ) Dantec 1899), has long since been discarded, and so has Population structure .06 ) an anti-Weismann theory of telegony (the first of two Total frequency .19 .00 males to mate with a female can influence the traits of the offspring sired by the second; this is not to be confused Physiology: with sperm precedence). Systems ) .07 H. C. Bumpus helped to bury the theory of telegony Growth .02 .05 by argument. His final sentence is prophetic in showing Reproduction .05 .02 Trade-offs .07 ) how a nineteenth-century problem would yield to a twentieth-century solution: “The vexed problems of heredity Total frequency .15 .15 never will be solved until a great many individuals or Behavior: institutions seriously undertake experimental breeding” Social .08 ) (Bumpus 1899, p. 922). The problem was of major im- Feeding .07 .07 portance; the solution, the discovery of genetics, was the Reproductive .05 .04 temporarily misplaced key that opened the door to the Total frequency .20 .11 major discoveries of the twentieth century and provided a truly novel way of achieving conceptual unification. Ecology: Population .21 .04 Community .15 .04 The Naturalist at the End of the Twentieth Century Total frequency .36 .08 In this century we have transformed our identity (Futuyma Morphology .07 .16 1998). We have dropped geology and petrography from Phylogeny .02 .02 our profile, weakened our dependence on traditional nat- Biogeography .02 .02 ural history (Mayr 1946; Dobzhansky 1966), and acquired Geology ) .04 newly invented disciplines such as genetics, unrecognizably Life histories ) .09 ) altered ones like ecology, and newly developed methods Systematics and synopses .25 ) of analysis such as mathematical modeling. Our mem- Oddities and miscellaneous .09 bership has increased enormously and has become more Total frequency .11 .67 international. We have grown in size and changed in shape. Total number of articles 121 55 To characterize the collective personality of the late Note: Some subjective judgment on relative impor- twentieth-century naturalist, I have done the modern thing tance had to be exercised when articles covered more of quantifying the publications in The American Naturalist. than one topic. Table 1 provides a crude classification of subjects covered by articles in volumes 151 and 152 published in 1998. For comparison I have included a similar list for volume 33, most, but not quite, exclusive categories. Herein lies a published in 1899. modern version of the disadvantage of specialization rec- The frequencies show the predominance of ecology, be- ognized at the end of the nineteenth century: specialization havior, and genetics in the modern naturalist. They do not by mode of investigation limits the degree of insightful reveal three extra characteristics of importance in the mod- and fruitful interaction between theoretical and empirical ern profile. First, evolution is a primary or secondary modes of inquiry. Third, crossing the boundaries of dis- theme of almost every article, mainly as adaptive expla- ciplines is a rewarding although still relatively rare habit. nation for observed phenomena (fig. 1), less as mechanism There are good examples of the value of transferring ideas of change, and least as history. Second, mathematical mod- from one field to problem solving in another (e.g., from eling (61 articles) is far more prevalent than laboratory neural physiology to explain feeding specialization). Nev- experimentation (25 articles) as a method of inquiry. Field ertheless, despite our declared emphasis on unification, studies, comprising experimentation (14 articles) and ob- synthesis is not the prime focus of most articles. servation (seven articles), take third place. These are al- Remarkably, Darwin is still quoted often (nine articles),

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The modern naturalist can therefore be characterized as basically an explorer and tester of evolutionary and ecological ideas that are developed to reveal and explain regularities in nature: in genetic structure as much as in phenotypic structure, and in ecological and behavioral function more than in physiological function. Explorations take us even farther afield than is indicated by the topics in table 1, and in two directions, the macroscopic and the microscopic. Missing from the table is paleoecology and the ecological exploration of evolution through deep time. For Wallace (1855, p. 190), “To discover how the extinct species have from time to time been replaced by new ones down to the very latest geological period, is the most difficult, and at the same time the most interesting problem in the natural history of the earth.” This task, and the companion one of determining why species have replaced each other, is as much a central problem in modern evolutionary biology as it was to Wallace (e.g., Graham et al. 1995; Knoll et al. 1996; Conway Morris 1998). It takes the modern form of trying to bring together a paleontological focus on patterns of evolution in relation to changing environments over millions of years and a neontological focus on observable and interpretable processes of microevolution in contemporary time. For example, Vermeij (1987) has used information about functional morphology of gastro- pod molluscs, their behavior and ecology inferred from comparative studies of living relatives, and independent Figure 1: A major activity of modern naturalists is searching for adaptive evidence of paleoenvironments to explain the large-scale explanations for structures and behaviors of organisms in nature. It is patterns of diversification of these well-fossilized animals. exemplified here by the cryptic coloration and posture of a bird, Nyctibius griseus (from Cott 1940, fig. 74). At the other end of the scale lie microscopic phenomena that occur within individual cells, including molecular genetic structure and function and the mechanisms of con- but no longer for the “old Darwinian principle of direct trol and regulation of development. Naturalists encounter benefit [of a trait] to its possessors.” Instead, he is cited a variety of organisms in nature and attempt to explain for his work on two enduring problems, the operation of sexual selection and the evolution of mating systems. what they find. While Marston Bates’s emphasis on the Comparison of today’s journal with that of 1899 reveals individual, singly or in groups, is still appropriate, the the differences across a century. A majority of the articles search for answers to many questions is being taken in- in 1899 have no counterpart in 1998, and evolution is not creasingly to cellular and macromolecular levels, into the a prominent feature of the 1899 literature. If anything, molecular realm of cytogenetic interactions and into the differences are understated by a simple listing. You cannot realm of molecular evolution for the reconstruction of tell from the table that parasite-host dynamics and ex- phylogeny. Perhaps this is the most fundamental change tinction are two preoccupations of modern ecologists that to the naturalists’ identity that has occurred this century. were not on the agenda 100 years ago. The emphasis in To illustrate with one example from hundreds, observed the earlier literature was firmly placed on a form of de- sex ratios in populations of the parasitic wasp Nasonia scriptive investigation that now plays only a subsidiary role vitripennis cannot be understood without a knowledge of in phylogeny, ecology, and behavior. Where modern stud- intracellular and intergenomic interactions with a bacterial ies of morphology are carried out with birds’ tails to test symbiont, Wolbachia (Werren 1998). At the end of the hypotheses of sexual selection, for example, 100 years ago twentieth century, we confront a natural history of ge- the colors of flowers and the structure of sea-pens were nomic structure and function that needs to be known in described because they were insufficiently known and were conjunction with a natural history of whole organisms for of interest for their own sake. a full understanding of diversity at the level of populations

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The scope for biological synthesis has never been and since then it “has shortened itself two hundred and greater. forty-two miles [by “cut-offs” of meandering loops]. ) Thus, my answer to the question posed in the title of Now, if I wanted to be one of those ponderous scientific this essay is, simply, that to be a naturalist is to ask ques- people, and ‘let on’ to prove ) what will occur in the far tions directly about organisms in nature and to seek an- future by what has occurred in late years, what an op- swers wherever they are to be found (macroecology, pop- portunity is here! ) Any person can see that seven hun- ulation genetics, etc.), by whatever means are available dred and forty-two years from now the Lower Mississippi (field experimentation, analysis of DNA, etc.). will be only a mile and three quarters long, and Cairo and New Orleans will have joined their streets together, and be plodding comfortably along under a single mayor and The Naturalist in the Twenty-First Century a mutual board of aldermen.” He then concluded with the What can be expected in the future? Just as at the begin- comment, “There is something fascinating about science. ning of this century, some current ideas are destined to One gets such wholesale returns of conjecture out of such be discarded and others will continue to be useful. Without a trifling investment of fact.” prescience it is risky to guess which will be which. This Undeterred by a high ratio of conjecture to fact, I an- reminds me of a story of a Harvard professor who told ticipate as one major development in the next century the his introductory class of medical students that half of what experimental reconstruction by genetic engineering of ex- they were about to be told was true and the other half tinct species or intermediate lineages between existing spe- would eventually be proved incorrect, the problem being cies. Now that we know how small changes in the timing that by the end of the course neither he nor the students of regulatory genes during early development can have would know which half was which. large effects on adult phenotype (Raff 1996), subject to The best predictor of tomorrow’s weather is today’s, environmental modulation, and how those genes acquire and in the same way and for the same reason, the best or are coopted for new functions, it becomes possible to guide to future research is contemporary research. Some alter phenotype by experimentally altering genes governing projections of current research axes into the future are development (fig. 2). For the task of reconstruction there clear to see. Six obvious choices are problems of under- are strong difficulties ahead. One is making a choice be- standing mammalian brain organization and function and tween alternative possible genetic constitutions of extinct their evolution, the evolution of human characteristics in species. Another is the assessment of interactions between our ancestors, the pattern of phylogeny and the process genotypes and environments. These difficulties will be of speciation, how complex communities of organisms are greatest for reconstructing taxa that have long since be- built up from simple ones and how they function, how come extinct without leaving behind even a single rep- genomic potential is translated into phenotypic reality resentative that could act as a blueprint for the rest. A through development and how that translation evolves, taxonomic neighbor will have to substitute. Some missing and the origin and early evolution of living things (see pieces in the tree of life will thus be filled in, however also Murphy and O’Neill 1995; Wilson 1998). It is also imperfectly and insecurely. In the process, much should safe to predict that a vastly richer understanding of the be learned about ancestral character states in phylogenies history of life will be achieved, in terms of phylogenetic and which developmental programs are viable, and why, relationships and the evolutionary origins of key traits and and which are not. All of this may help us to make far processes. Furthermore, the rate and directions of progress better evolutionary sense of patterns of diversification of will be strongly influenced by the development of new organs and organisms and of some of the major transitions techniques. In this century we have seen what the electron in organization (Maynard Smith and Szathma´ry 1995) microscope has done for cytology, what computers have than is possible today. done for quantitative biology, and what the polymerase Other missing pieces will be filled in by the less dramatic chain reaction, cloning, and DNA sequencing have done and more traditional methods of excavating fossils and for molecular genetics. Recovering evolutionary history searching for new species of micro- and macroorganisms will proceed faster as a result of new technologies yet to in tropical rainforests and depths of the ocean, in caves be conceived, let alone developed. and in ice caps. Exploration and discovery, which played I would like to go farther, while at the same time being such a large role in the activities of nineteenth-century mindful, like Mark Twain (1883), of the dangers of ex- naturalists, still offer abundant scope to the twenty-first- trapolating too far from known facts into the realm of the century naturalists. It has been estimated that many mil- ridiculous. He wrote (1883, pp. 207–208), “The Mississippi lions of species, perhaps 10 million or more, await sci- between Cairo and New Orleans was twelve hundred and entific discovery and description (Wilson 1992; Stork fifteen miles long one hundred and seventy-six years ago,” 1997). If this is not enough encouragement for the sys-

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as Takhtajania perrieri, the only extant African or Mada- gascan representative of the primitive plant family Win- teraceae (Schatz et al. 1998). Modern extinctions (Stearns and Stearns 1999) spice this encouragement with urgency. Genetic engineering and discovery of new species and higher taxa will give us a better appreciation of how the tree of life diversiﬁed. By themselves they will provide only partial enlightenment on why it diversiﬁed in the way that it did. Interpreting evolutionary history requires a knowledge of genetics of organisms and their environments as well as of their interaction. Here I would like to raise a concern about the future of our society, as well as society in general, and the future of naturalists whose work is done out of doors in moderately wild places. It is that environments that are the products of natural processes have been and are continuing to be degraded and de- stroyed at an unprecedented rate (Lubchenko et al. 1991). As a result we are losing parts of life’s history that would appear to be unrecoverable except, to an unknown and probably limited extent, by the process of genetic engineering referred to above (which is no cause for compla- cency). We are reducing the means of interpreting the history as well, to the degree that present-day natural environments provide critical information about the natural relationship between organisms and their environments in the past. Fortunately, there is unprecedented awareness of environmental deterioration and preparedness to do something about it (Reaka-Kudla et al. 1997; Lubchenko 1998) and, in the case of global climate change, to learn from it (Travis and Futuyma 1993).

The Field Naturalist in the Future Expressing concern about deterioration of the environment has been going on for a long time. It is to be found in the writings of Darwin and Wallace, for example, and in contemporaries of theirs such as Henry Moseley (1879), who went around the world on a famous research vessel, the Challenger, 40 years after the voyage of the Beagle, for about the same length of time as the Beagle. In this century, Figure 2: Will it be possible in the future to experimentally alter de- Our Plundered Planet (Osborn 1948) and Silent Spring velopment by genetic manipulation and thereby reconstruct the missing (Carson 1962) sounded the alarm with more than their common ancestor of extant species such as these two beetles, Onthophagus unequivocal titles (also Hynes 1960; Rudd 1964), and one taurus (upper) and Onthophagus praecellens (lower)? (Illustrations from D. J. Emlen, personal communication; each beetle is approximately 1 cm encounters this alarm with increasing frequency in books, in length.) the ecological literature, and the popular press. Conser- vation societies and journals have sprung up in response to the alarm to create awareness of the problems and to tematics branch of the modern naturalists, then surely it seek scientiﬁc as well as political remedies. An element of is given by such discoveries as an extraordinary new in- siege mentality prevails in the community (for examples vertebrate phylum, the Cycliophora (Funch and Kristensen see Stearns and Stearns 1999). From this literature I have 1995); evidence of a new kingdom, the archaebacteria chosen two passages to quote for their combination of (Barnes et al. 1996; McInerney et al. 1997; see also Mayr passion, eloquence, and relevance to evolutionary biology. 1998); and rediscoveries of apparently extinct species such The ﬁrst, by Gentry (1989), concludes a discussion of ex-

This content downloaded from 128.103.149.52 on Thu, 26 Feb 2015 12:48:14 PM All use subject to JSTOR Terms and Conditions Naturalists Past, Present, and Future 7 traordinarily high rates of plant speciation in the cloud extinction, which themselves are increasing in frequency. forests of Ecuador, coupled with a sobering account of an Yet as these quotations show, it is highly relevant to the extraordinarily high rate of extinction of local endemics society’s goals for two main reasons. First, and most ob- resulting from deforestation, as follows: “Not only is man- vious, extinctions and loss of habitat deprive us of what kind’s biological heritage poorer as a result [of defores- we have chosen to study. For astrophysics the equivalent tation], but our intellectual heritage is also eroded as these would be losing several percent of the stars in the universe uniquely active laboratories of speciation disappear from each century because of human activities in some hypo- the face of the earth. Moreover, those of us interested in thetical way. I cannot imagine that astrophysicists would evolutionary processes have an added incentive for pre- keep the problem to themselves, or even turn a blind eye serving our planet’s dwindling remnants of tropical forest: to what was happening just as long as they had a few We need them if we hope ever to truly understand the trillion stars left to work with. processes of speciation and evolution that have given rise Second, and less obvious, the remnants of natural en- to the diversity of life on earth” (Gentry 1989, p. 127). vironments and their occupants color our view of natural Henry Moseley had written about the extinction of ter- processes, and such views may be distorted. Terrestrial restrial species 100 years earlier (“Animals and plants ) habitats are fragmented by human activities, landscapes are rapidly perishing day by day, and will soon be, like are reconfigured, waterways are polluted, top predators the Dodo, things of the past ) for ever a gap in the disappear, extraneous species are introduced, others are knowledge of mankind.” [Moseley 1879, p. 519]) but introduced to “control” them yet control or eliminate na- thought that the deep marine environment was safe tive species instead, community composition becomes al- enough for scientists to study at their leisure. Here, though, tered, species dependencies change, and those species with is what Paul Dayton has to say about the effects of the weedy characteristics tend to predominate—all of this in fishing industry on the composition of communities in the name of human welfare or tradition. marine environments: The changes themselves are not without biological interest. They can throw light on ecological properties such One inescapable consequence of this widespread damage is as community stability (Chapin et al. 1997; Vitousek et al. the loss of the opportunity to study and understand intact 1997) and evolutionary processes such as the evolution of communities. In most cases there are no descriptions of the cryptic coloration (Kettlewell 1973; Majerus 1998), sexual pristine habitats. The damage is so pervasive that it may be selection, and speciation (Seehausen et al. 1997; Feder impossible ever to know or reconstruct the ecosystem. In fact, 1998). But the resulting communities and their function- each succeeding generation of biologists has markedly different ing can hardly be held up as a model of the natural state. expectations of what is natural because they study increasingly Yet we are in danger of doing just that, especially, I believe, altered systems that bear less and less resemblance to the for- in theoretical investigations where conceptions (and per- mer, preexploitation versions. This loss of perspective is ac- ceptions) of the world we inherit are brought to bear on companied by fewer direct human experiences (or even mem- the delimitation of a problem, assumptions of models that ories) of once undisturbed systems. The effects of humans are used to search for a solution, the interpretation of its sometimes result in cascading ecological changes—a void often solution, and then in external validation through empirical in part filled with introduced or inappropriate imposters that work. replace and mask the traces of the former natural system—but An appropriate icon for this worrying trend is Albrecht the species often simply disappear, leaving no conspicuous Du¨rer’s woodcut of the Indian rhinoceros brought to Eu- effect on the community. As with the loss of human cultures rope (Lisbon) in 1515. Du¨rer did not see the animal but and languages after the passing of the elders with their wisdom, made the woodcut from descriptions and sketches pro- so too is humanity losing the evolutionary wisdom found in vided to him, committing a small error in the form of a intact ecosystems (Dayton 1998, p. 821). gratuitous, unicorn-like, spiral horn on the shoulders. De- “Seek simplicity and distrust it”; so runs Whitehead’s rivative artists made further copying errors (fig. 3), adding (1920, p. 163) “guiding motto in the life of every natural to the faithfully reproduced yet erroneous spine over the philosopher.” To this I would add a corollary: seek gen- course of the next two centuries. Fortunately, the rhinoc- erality and distrust it. In the less diverse world of the eros did not become extinct, and representations of the future, it will be increasingly easy to find both simplicity animal were eventually brought into line with reality (Cole and generality, yet, with some irony, increasingly necessary 1953). to distrust them. The difficult question to answer is: How far wrong do Environmental concern is not a message that appears we go in taking a human-altered environment as a proxy often in the pages of The American Naturalist, although it for a natural one and a cardboard cutout view of the is increasingly present as subtext to ecological articles on natural world as exemplified, for example, by paintings of

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biota does matter. It matters seriously when we attempt to interpret particular details of the evolutionary history of organisms in terms of observable components and processes in their contemporary environments. I will illustrate the last point with an example. On the island of Mauritius, a tree, Calvaria major (Sapotaceae), produces large fruits that do not germinate or that germinate very rarely. Not surprisingly, the population has declined toward extinction. The reproductive biology of the species cannot be interpreted confidently in evolutionary terms because possible agents that facilitated the germination of the fruit are missing. One suggested missing agent is the digestive tract of the dodo (Raphus cucullatus; Vaughan and Wiehe 1941; Temple 1977), absent from the island for more than 350 years as a result of direct and indirect effects of human occupation. In this example, knowledge of the predisturbance Mauritius community was sufficient, even though meager, for these au- thors to speculate about the missing factor. Moreover, ob- servations of basalt rocks the size of golf balls in the gut of dodos (Temple 1983) and experiments with turkeys (Temple 1977) as a substitute for dodos demonstrated the plausibility of the hypothesis that passage through the gut of a large avian herbivore was essential or almost essential for germination (fig. 4). The hypothesis that gut passage was essential has nevertheless been much debated (Owa- dally 1979; Temple 1979, 1983, 1984; Cheke et al. 1984; Vaughan 1984). That debate is my main point. Essential,

Figure 3: Models of the natural world can mislead when based on partial information. Albrecht Du¨rer’s woodcut of an Indian rhinoceros brought to Lisbon, Portugal, in 1515 (upper) is an exemplar. It served as a model for artists for the next 150 years, and the erroneous spine on the shoulder was faithfully copied by them, for example, by Tempesta, in 1650 (lower; from Cole 1953, ﬁgs. 3, 15). nature “in the raw” by Henri Rousseau (e.g., see the cover of issues of Animal Behaviour)? Ecologically we can go seriously astray (e.g., see Hedin et al. 1995), but is the same true for evolutionary studies? For some parts of evolutionary biology the answer is no. We do not need natural environments to understand the principles of natural selection, sexual selection, genetic drift, frequency dependence, epistasis, and so forth, or the Wrightian concept of Figure 4: Extinction reduces our ability to interpret evolutionary history. an adaptive landscape. The whole gamut of intracellular For example, the reproductive biology of a tree, Calvaria major (Sapo- evolutionary interactions between different genomes is taceae), on Mauritius cannot be conﬁdently interpreted in evolutionary played out without dependence on particular environ- terms because possible agents that facilitated the germination of the large ments external to the organisms, or so it appears. Phy- and thick-walled fruit are missing. One suggested missing agent is the logenies can be reconstructed from comparisons of mi- digestive tract of the extinct dodo (Raphus cucullatus); passage through the gut of this large avian herbivore may have been almost essential for tochondrial DNA molecules without any knowledge of the germination (from a painting by Tracy Pederson, reproduced here with environments the taxa occupy or occupied. However, for permission of Visual Resources for Ornithologists [VIREO], Academy of other parts of evolutionary biology, the loss of natural Natural Sciences, Philadelphia).

This content downloaded from 128.103.149.52 on Thu, 26 Feb 2015 12:48:14 PM All use subject to JSTOR Terms and Conditions Naturalists Past, Present, and Future 9 helpful, or irrelevant, the role of the dodo can now no “reckless generalization” that “nothing makes sense in bi- longer be known and must forever remain conjectural. ology except in the light of evolution” (Dobzhansky 1964, This is no isolated case. The evolution of some Neo- p. 449), providing it is preceded by the word “ultimately,” tropical fruit characteristics (Janzen and Martin 1982), the since not all biologists who would call themselves natu- evolution of leaf form in some Hawaiian plants (Givnish ralists pay attention to it or even feel the need to. For et al. 1994; see also James and Burney 1997), and the example, an ecologist’s world can make perfect sense, in pollination biology of certain Opuntia cactus species and the short term at least, in the absence of evolutionary why they hybridize (Janzen 1986) cannot be known in the considerations. Moreover, there are other organizing prin- absence of some key missing herbivores, dispersal agents, ciples that fall outside evolutionary biology yet illuminate and pollinators, now extinct as a result of human activities. it, such as physical laws of thermodynamics and scaling Another way of appreciating the same problem is to ask (e.g., West et al. 1997). what our store of evolutionary knowledge would be if Unification requires a common language, and mathe- several twentieth-century model systems in evolutionary matics is a common language. Pages of the modern Amer- biology had gone the way of the dodo before the century ican Naturalist are filled with ideas creatively explored in began, for example, the silverswords and Drosophila of the language of mathematics. J. B. S. Haldane once wrote Hawaii; or stalk-eyed flies and guppies; Helianthus sun- somewhere that “An ounce of mathematics is more con- flowers and Heliconius butterflies; Caribbean Anolis lizards; vincing than a ton of verbal argument.” It is easy to see Daphnia of holarctic lakes and haplochromine cichlid fish his point. Nonetheless, there is an ever-present danger that of the African rift lakes; Arabidopsis, Caenorhabditis, and mathematics will be thought to say more than it does zebra fish? And what might we have lost without knowing (Hogben 1937), especially when interpreted beyond the we had lost it, or how to use it? domain of its applicability. Excessive use of mathematics I have continued at length on the precariousness of what has been lampooned in a joke, which I have heard twice, can be called habitat-dependent evolutionary biology be- to the effect that the society is now dedicated to the con- cause natural history of this sort is becoming increasingly ceptual unification of the mathematical sciences. Yet there unnatural history. In contrast to the long-term prospects are limits to the degree to which the complexity of the of field naturalists, all the other activities listed in table 1 natural biological world can be captured by this language. appear to have a healthy future. Much of that complexity resides in the ton of verbal argument, and discarding it is either desirable or not, de- pending on whether you believe that, metaphorically, a The Society’s Goal: Unification of the deity (Paley) or the devil (Einstein) is in the details. This Biological Sciences polarization reflects a permanent tension between the drive The American Naturalist started off being “Dedicated to to generalize and the realization that nature is too diverse the Unification of the Biological Sciences,” was changed to be reduced to a simple set of statements. On this theme to “Devoted to the Advancement and Correlation of the I have one final point to make. Biological Sciences,” and then, as recently as 1977, essen- Concern over fragmented specializations motivated the tially returned to a stronger version of the original goal, society’s desire for conceptual unification at the end of the to be “Devoted to the Conceptual Unification of the Bi- last century. A hundred years later, the need for conceptual ological Sciences.” The key words here are “conceptual unification is, if anything, greater, as collectively we are a unification.” The American Society of Naturalists is more generalist population than ever before, yet we are uniquely suited to this goal by virtue of the breadth of the individually more specialized. Modern specialization takes naturalists’ mandate to explain biological diversity. We different forms. I have referred to one already, speciali- seek unity without sacrificing diversity, and we seek ex- zation by mode of scientific inquiry. Another is an intense planations for diversity in as unified a manner as possible. focus on model systems. We celebrate outstanding suc- I believe we can do a better job of this if we are more cesses from concentration of effort on a few “tractable” conscious, more explicitly aware, of the desirability of syn- systems, but at the same time we should be concerned thesis at as high a level of integration as is within our that they come at a certain cost of breadth. This cost may reach. I say this as a consumer of The American Naturalist. be experienced more in evolutionary biology than in ecol- How is conceptual unification best sought and achieved? ogy. Model systems are widely spaced on the taxonomic There is more than one answer; I will offer a couple. Like landscape (Nijhout 1994) and yield different results and many others I see the best pathway through the study of insights. It is the differences that give rise to a problem; evolution (e.g., Smocovitis 1996). Disparate areas of bi- generalizing confidently from them is difficult. The remedy ology are united by evolutionary principles that apply to is to pay more attention to the intervening taxa that are them all. Few biologists would quarrel with Dobzhansky’s relatively or entirely neglected so as to obtain a better grasp

This content downloaded from 128.103.149.52 on Thu, 26 Feb 2015 12:48:14 PM All use subject to JSTOR Terms and Conditions 10 The American Naturalist of how far an understanding of one set of organisms can to eat in order to live, equips us with an appetite and be extended to others. rewards us with pleasure.) Additional rewards will come from transferring concepts from one field to another, concepts such as trade- Acknowledgments offs, fractal dimensions, chaos, metapopulations, inclusive I thank B. R. Grant and H. S. Horn for valuable discussion fitness, and the like. Out of such transfers are born new and comments on the manuscript, D. J. Emlen for figure insights, new ways of looking at problems, even new ways 2, and S. A. Temple for help in locating figure 4. of looking at old solutions, and a better appreciation of unity at a time when various economic factors such as Literature Cited research grants and social forces associated with career advancement encourage specialization and the fragmen- Barnes, S. M., C. F. Delwiche, J. D. Palmer, and N. R. Pace. tation of biology. As an example from within biology, 1996. Perspectives on Archaeal diversity, thermophily transfer of the concepts of variation and selection from and monophyly from environmental rRNA sequences. population genetics to cell biology has led to new insights Proceedings of the National Academy of Sciences of the into epigenetic phenomena such as “overproduction” of USA 93:9188–9193. mitotic microtubules (Kirschner 1992; Gerhart and Kir- Bates, H. W. 1863. The naturalist on the river Amazons. schner 1997). Microtubules not only perform a vital func- Dent, London. tion but they also generate flexibility that is believed to Bates, M. (1950) 1990. The nature of natural history. facilitate evolutionary change (Kirschner 1992). This ex- Princeton University Press, Princeton, N.J., with a new ample, and similar ones of transient excesses of synapses preface by H. S. Horn. Original edition, Scribners, New and neurons in mammalian neuromuscular development York. (Brown et al. 1991; Jacobson 1991) and “overproduction” Belt, T. 1874. The naturalist in Nicaragua. Bumpas, of song types by young birds (Marler and Peters 1982), London. may be relevant to Haldane’s (1958, p. 12) speculation Bigelow, R. P. 1898. The aim of the American Naturalist. that “many of the major features of evolution were due American Naturalist 32:49–51. to the fact that some groups kept possibilities open which Brillat-Savarin, A. 1826. Physiologie du Gout, ou Me´di- others did not.” Now there is an interesting idea worth tations de Gastronomie Transcendente. Vol. 1. Sautelet, pursuing in the twenty-first century (e.g., see Wagner et Paris. al. 1999)! Brown, M. C., W. G. Hopkins, and R. J. Keynes. 1991. In conclusion, I believe that the society’s mission of Essentials of neural development. Cambridge University unification can be achieved by a broad, evolution-centered Press, Cambridge. approach to explaining all of organic diversity: the origin Bumpus, H. C. 1899. Facts and theories of telegony. Amer- and evolution of organisms and their behavioral and phys- ican Naturalist 33:917–922. iological functioning as individuals and their ecological Carson, R. 1962. Silent spring. Houghton-Mifflin, Boston. functioning as interacting populations in communities. Chapin, F. S., III, B. H. Walker, R. J. Hobbs, D. U. Hooper, This approach seeks an understanding across the biological J. H. Lawton, O. E. Sala, and D. Tilman. 1997. Biotic spectrum and at all levels of biological organization in an control over the functioning of ecosystems. Science integrated manner by employing mathematics as the lan- (Washington, D.C.) 277:500–504. guage of choice where possible, but not exclusively; by Cheke, A. S., T. Gardner, C. G. Jones, A. W. Owadally, and encouraging new syntheses of ideas and information across F. Staub. 1984. Did the dodo do it? Animal Kingdom disciplines and modes of investigation; and by inviting 87:4–6. nonmembers from disciplines not well represented in the Cole, F. J. 1953. The history of Albrecht Du¨rer’s rhinoceros society to join the enterprise. in zoological literature. Pages 337–356 in E. A. Under- wood, ed. Science, medicine and history. Vol. 1. Oxford University Press, London. Coda Conway Morris, S. 1998. The crucible of creation: the I began by using the fourth aphorism of Brillat-Savarin Burgess Shale and the rise of animals. Oxford University (1826) to introduce the analogy of a consumer society, Press, New York. and I conclude with his fifth aphorism as an analogy of Cott, H. B. 1940. Adaptive coloration in animals. Oxford the value, if not the necessity, of reading The American University Press, New York. Naturalist: “Le Creáteur, en condamnant l’homme a` man- Davenport, C. B. 1899. Statistical methods with special ger pour vivre, l’y invite par l’appe´tit, et l’en rećompense reference to biological variation. Wiley, New York. par le plaisir.” (The creator, while condemning mankind Dayton, P. K. 1998. Reversal of the burden of proof in

This content downloaded from 128.103.149.52 on Thu, 26 Feb 2015 12:48:14 PM All use subject to JSTOR Terms and Conditions Naturalists Past, Present, and Future 11

fisheries management. Science (Washington, D.C.) 279: Hogben, L. 1937. Mathematics for the million. Norton, 821–822. New York. Dobzhansky, T. 1964. Biology, molecular and organismal. Huxley, J. S. 1940. Introduction. Pages vii–ix in H. B. Cott, American Zoologist 4:443–452. ed. Adaptive coloration in animals. Oxford University ———. 1966. Are naturalists old-fashioned? American Press, New York. Naturalist 100:541–550. Hynes, H. B. N. 1960. The biology of polluted waters. Driesch, H. 1899. Die Localisation morphogenetisches Liverpool University Press, Liverpool. Vorga¨nge: ein beweis vitalischen Geschehens. Archiv fu¨r Jacobson, M. 1991. Developmental neurobiology. 3d ed. Entwicklungsmechanik 8:35–111. Plenum, New York. Edes, R. T. 1899. Relation of the chirping of the tree cricket James, H. F., and D. A. Burney. 1997. The diet and ecology (Oecanthus niveus) to temperature. American Naturalist of Hawaii’s extinct flightless waterfowl: evidence from 33:935–938. coprolites. Biological Journal of the Linnean Society 62: Feder, J. L. 1998. The apple maggot fly, Rhagoletis po- 279–297. monella: flies in the face of conventional wisdom about Janzen, D. H. 1986. Chihuahuan desert nopaleras: de- speciation? Pages 130–144 in D. J. Howard and S. H. faunated big mammal vegetation. Annual Review of Berlocher, eds. Endless forms: species and speciation. Ecology and Systematics 17:595–636. Oxford University Press, Oxford. Janzen, D. H., and P. S. Martin. 1982. Neotropical anach- Funch, P., and R. M. Kristensen. 1995. Cycliophora is a ronisms: the fruits the gomphotheres ate. Science new phylum with affinities to Entoprocta and Ecto- (Washington, D.C.) 215:19–27. procta. Nature (London) 378:711–714. Kettlewell, B. 1973. The evolution of melanism. Clarendon, Futuyma, D. J. 1998. Wherefore and whither the naturalist? Oxford. American Naturalist 151:1–6. Kirschner, M. 1992. Evolution of the cell. Pages 99–126 Gabaccia, D. R. 1998. We are what we eat: ethnic food in P. R. Grant and H. S. Horn, eds. Molds, molecules, and the making of Americans. Harvard University Press, and metazoa: growing points in evolutionary biology. Cambridge, Mass. Princeton University Press, Princeton, N.J. Gentry, A. H. 1989. Speciation in tropical forests. Pages Knoll, A. H., R. K. Bambach, D. E. Caulfield, and J. P. 113–134 in L. B. Holm-Nielsen, I. C. Nielsen, and H. Grotzinger. 1996. Comparative earth history and late Balsev, eds. Tropical forests: botanical dynamics, spe- Permian mass extinction. Science (Washington, D.C.) ciation and diversity. Academic Press, New York. 273:452–457. Gerhart, J., and M. Kirschner. 1997. Cells, embryos, and Le Dantec, F. 1899. La sexualite´. Scientia, se´ries biologique, evolution: toward a cellular and developmental under- no. 2. Carre´ et Naud, Paris. standing of phenotypic variation and evolutionary Lubchenko, J. 1998. Entering the century of the environ- adaptability. Blackwell Science, Oxford. ment: a new social contract for science. Science (Wash- Gerrould, J. H. 1899. A rational vitalism. American Nat- ington, D.C.) 279:491–497. uralist 33:967–972. Lubchenko, J., A. M. Olson, L. B. Brubaker, S. R. Car- Givnish, T. J., K. J. Sytsma, J. F. Smith, and W. J. Hahn. penter, M. M. Holland, S. P. Hubbell, S. A. Levin, et al. 1994. Thorn-like prickles and heterophylly in Cyanea: 1991. The sustainable biosphere initiative: an ecological adaptations to extinct avian browsers on Hawaii? Pro- research agenda. Ecology 72:371–412. ceedings of the National Academy of Sciences of the Majerus, M. E. N. 1998. Melanism: evolution in action. USA 91:2810–2814. Oxford University Press, Oxford. Gould, S. J. 1997. Questioning the millennium: a ration- Marler, P., and S. Peters. 1982. Developmental over- alist’s guide to a precisely arbitrary countdown. Har- production and selective attrition: new processes in the mony, New York. epigenesis of birdsong. Developmental Psychobiology Graham, J. B., R. Dudley, N. M. Aguilar, and C. Gans. 15:369–378. 1995. Implications of the late Palaeozoic oxygen pulse Maynard Smith, J., and E. Szathma´ry. 1995. The major for physiology and evolution. Nature (London) 375: transitions in evolution. W. H. Freeman, New York. 117–120. Mayr, E. 1946. The naturalist in Leidy’s time and today. Haldane, J. B. S. 1958. The theory of evolution, before Proceedings of the Academy of Natural Sciences of Phil- and after Bateson. Journal of Genetics 56:1–17. adelphia 98:271–276. Hedin, L. O., J. J. Armesto, and A. H. Johnson. 1995. ———. 1998. Two empires or three? Proceedings of the Patterns of nutrient loss from unpolluted, old-growth National Academy of Sciences of the USA 95: temperate forests: evaluation of biogeochemical theory. 9720–9723. Ecology 76:493–509. McInerney, J. O., M. Mullarkey, M. E. Wernecke, and R.

This content downloaded from 128.103.149.52 on Thu, 26 Feb 2015 12:48:14 PM All use subject to JSTOR Terms and Conditions 12 The American Naturalist

Powell. 1997. Phylogenetic analysis of Group I marine ———. 1983. The dodo haunts a forest. Animal Kingdom archaeal rRNA sequences emphasizes the hidden diver- 86:20–25. sity within the primary group Archaea. Proceedings of ———. 1984. Author Stanley Temple replies. Animal the Royal Society of London B, Biological Sciences 264: Kingdom 87:7, 51. 1663–1669. Travis, J., and D. J. Futuyma. 1993. Global change: lessons Moseley, H. N. 1879. Notes by a naturalist on the Chal- from and for evolutionary biology. Pages 251–263 in P. lenger. J. Murray, London. M. Kareiva, J. G. Kingsolver, and R. B. Huey, eds. Biotic Murphy, M. P., and L. O’Neill, eds. 1995. What is life? the interactions and global change. Sinauer, Sunderland, next fifty years: speculations on the future of biology. Mass. Cambridge University Press, Cambridge. Twain, M. 1883. Life on the Mississippi. Osgood, Boston. Nijhout, H. F. 1994. Insect hormones. Princeton University Vaughan, R. E. 1984. [Response to Temple]. Animal King- Press, Princeton, N.J. dom 87:6–7. Nutting, C. S. 1899. The utility of phosphorescence in Vaughan, R. E., and P. O. Wiehe. 1941. Studies on the deep-sea animals. American Naturalist 33:793–799. vegetation of Mauritius. III. The structure and devel- Osborn, H. F. 1948. Our plundered planet. Scribner, New opment of the upland climax forest. Journal of Ecology York. 29:127–160. Owadally, A. W. 1979. The dodo and the tambalacoque Vermeij, G. J. 1987. Evolution and escalation: an ecological tree. Science (Washington, D.C.) 203:1363–1364. history of life. Princeton University Press, Princeton, Raff, R. 1996. The shape of life: genes, development, and N.J. the evolution of animal form. University of Chicago Vitousek, P., H. A. Mooney, J. Lubchenko, and J. M. Press, Chicago. Melillo. 1997. Human domination of earth’s ecosys- Reaka-Kudla, M. L., D. E. Wilson, and E. O. Wilson, eds. tems. Science (Washington, D.C.) 277:494–499. 1997. Biodiversity. Vol. 2. Understanding and protecting Wagner, G. P., C.-H. Chiu, and T. F. Hansen. 1999. Is Hsp our biological resources. Joseph Henry, Washington, 90 a regulator of evolvability? Journal of Experimental D.C. Zoology 285:116–118. Rudd, R. L. 1964. Pesticides and the living landscape. Uni- Wagner, M. 1889. Die Entstehung der Arten durch Raüm- versity of Wisconsin Press, Madison. liche Sonderung. Benno Schwalbe, Basel. Schatz, G. E., P. P. Lowrey II, and A. Ramisamihantanirina. Wallace, A. R. 1855. On the law which has regulated the 1998. Takhtajania perrieri rediscovered. Nature (Lon- introduction of new species. Annals and Magazine of don) 391:133–134. Natural History, Series 2, 16:184–196. Seehausen, O., J. J. M. van Alphen, and F. Witte. 1997. ———. 1871. Contributions to the theory of natural se- Cichlid fish diversity threatened by eutrophication that lection: a series of essays. 2d ed. Macmillan, New York. curbs sexual selection. Science (Washington, D.C.) 277: Werren, J. H. 1998. Wolbachia and speciation. Pages 1808–1811. 245–260 in D. J. Howard and S. H. Berlocher, eds. End- Smocovitis, V. B. 1996. Unifying biology: the evolutionary less forms: species and speciation. Oxford University synthesis and evolutionary biology. Princeton University Press, Oxford. Press, Princeton, N.J. West, G. B., J. H. Brown, and B. J. Enquist. 1997. A general Stearns, B. P., and S. C. Stearns. 1999. Watching, from the model for the origin of allometric scaling laws in bi- edge of extinction. Yale University Press, New Haven, ology. Science (Washington, D.C.) 276:122–126. Conn. Whitehead, A. N. 1920. The concept of nature. Tarner Stork, N. E. 1997. Measuring global diversity and its de- Lectures delivered in Trinity College, November, 1919. cline. Pages 41–68 in M. L. Reaka-Kudla, D. E. Wilson, Cambridge University Press, London. and E. O. Wilson, eds. Biodiversity. Vol. 2. Understand- Wilson, E. O. 1992. The diversity of life. Norton, New ing and protecting our biological resources. Joseph York. Henry, Washington, D.C. ———. 1998. Consilience: the unity of knowledge. Knopf, Temple, S. A. 1977. Plant-animal mutualism: co-evolution New York. with dodo leads to near extinction of plant. Science (Washington, D.C.) 197:885–886. ———. 1979. Response to Owadally (1979). Science (Washington, D.C.) 203:1364. Associate Editor: Joseph Travis

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