Perspectives in Biology and Medicine

THE EMERGENCE OF EVOLUTIONARY AND COMMUNITY ECOLOGY AS EXPERIMENTAL SCIENCES STEPHEN C. STEARNS* I. Introduction A short essay on 25 years of progress in a complex field could take many forms. This one reflects my evolutionary and experimental bias. Others have traced the recent history of ecology and described controversies over concepts, methods, and research strategies [1-12]. I have emphasized studies that bear on two questions: What do we now know that is reliable, exciting, and surprising that we did not know in 1956? What did we think we knew in 1956 that we now know is false? The studies discussed in this paper are primarily experimental tests of precisely stated, concrete hypotheses, executed in tractable model systems. This is no coincidence: I selected those studies because I admire that kind of science. Others would differ. However, the fact that this paper could be written in 1981 indicates that ecology has changed considerably since 1956, and that a model of "good science" that applies in many other fields can also be applied with impressive results in a field that some contend is too complex for experimental analysis. In 1956, great emphasis was placed on the analysis of particular environmental factors (heat, light, humidity, and so forth), on population dynamics, on interactions between species (competition and prédation), and on the descriptive classification of habitats (biomes, biocoenoses). The major controversy of the day had begun in the 1930s and centered on the mode of regulation of natural populations: were they regulated by density-dependent factors like competition and prédation, or were The author expresses his thanks to Jim Collins, Frank Pitelka, Ron Pulliam, Pete Myers, Jamie Smith, Frank Gill, Don Whitehead, Stan Dodson, Bob Paine, Bill Neill, and Nelson Hairston for their many conversations which helped in developing the outline for this paper. He is also grateful toJamie Smith, Jim Collins, Piet den Boer, and Rie Charnov for their detailed comments. ?Biological Laboratories, Reed College, Portland, Oregon 97202. O 1982 by The University of Chicago. AU rights reserved. 003 1-5982/82/2504-0306$01 .00 Perspectives in Biology and Mediane, 25, 4 ¦ Summer 1982 | 621 they regulated by density-independent factors like weather? Some attention was paid to the roles of ecology in evolution and of evolution in ecology, but few experiments were done, few hypotheses were tested. We are most often impressed by work that is concrete, simple, testable, general, and replicable. Such studies make us feel we now understand something that is important and even surprising in a way that we did not understand it before. Advances in ecology since 1956 which give me that feeling fall into two areas: evolutionary ecology and community structure . II. Notable Advances in Evolutionary Ecology In 1956, evolution and ecology could be studied separately. By 1981, parts of ecology were transformed by evolutionary theory, creating a new specialty, evolutionary ecology, the basic insight of which is that many whole-organism traits can be viewed as solutions to particular environmental problems. The area most affected was formerly called population ecology and ethology—the study of the interactions of whole organisms with one another and with their environments. The advances can be grouped (somewhat arbitrarily) into five areas: sociobiology, sex allocation, foraging, life-history evolution, and group selection. a. sociobiology Sociobiology arose recently and has generated as much loose speculation as it has critical analysis; many of its ideas remain controversial. However, it contains a core of three ideas with potentially far-reaching implications: first, degree of relationship influences kind of behavior through kin selection [13-15]; second, social behavior—in particular, the breeding system—can be an adaptation to ecological circumstances, especially to food type and distribution [16, 17]; third, organisms can be usefully conceived as selfish players in a game scored in terms of effective reproduction [18, 19]. Thus sociobiology is a hybrid formed by the merger of genetics, ecology, and game theory. Kin selection assumes that only genes matter, that helping relatives also helps one's genes, and that in the extreme an organism will forgo reproduction or sacrifice itself to save relatives. One key insight led to its initial, persuasive confirmation: the unusual mode of inheritance in bees...