Showing papers in "Annual Review of Ecology, Evolution, and Systematics in 1975"

Cannibalism in Natural Populations

Abstract: Cannibalism, defined as intraspecific predation, is a behavioral trait found in a wide variety of animals, although most references to this behavior are anecdotal or based on casual laboratory observations, The role of cannibalism in the dynamics of natural populations has been largely neglected; the most elegant and detailed analy­ ses of the population consequences of cannibalism are still provided by laboratory studies of flour beetles (Tribolium) that describe the process, examine its interac­ tions with other population processes, and attempt to derive generalities about its effects (60, 78, 88), Therefore, some authors have suggested that cannibalism is an artifact of laboratory systems (20, p, 324) or that it occurs only in cases of severe stress, especially when alternatives, such as dispersal, are not possible (I05), My purpose in this review is to show that cannibalism is a normal phenomenon in many natural populations, to evaluate its possible roles in influencing demo­ graphic structure and population processes, and to suggest conditions for, and constraints on, its occurrence, Cannibalism may be an interaction that reduces population size before acute resource shortage causes severe physiological stress, and in this sense its effects may be analogous to those of spacing behavior or dominance hierarchies in some social animals (104), I also discuss cannibalism as a limiting case of predator-prey interactions among potential competitors, This review is based mainly on field experiments and direct estimates of rates of cannibalism, but I use papers describing laboratory experiments to supplement the discussion of behavioral triggers and genetic components and to fill gaps in the field evidence, I have excluded numerous references with only casual mention of canni­ balistic events,

Modes of Animal Speciation

Abstract: The study of speciation is an ad hoc science. No one has yet observed the develop­ ment from beginning to end of a new plant or animal species in nature. The fossil record, so useful in painting a broad picture of long-term evolutionary trends, lacks the temporal and biological sensitivity to dissect the multitude of processes involved in speciation. Population genetics, the extreme opposite of paleontology in its ability to measure and model gene frequency changes and stability, has also failed to provide much insight into the genetics of speciation (110). At the molecular level, proteins used in the current flush of allozyme studies (110, 158, 174) have almost no direct bearing on speciation. Estimates of genetic differen­ tiation based on allozyme data alone (i.e. 147, 189), therefore, provide only crude indexes of genetic divergence between species and so-called semispecies, most of which could easily be regarded as species (178). Moreover, animals used in these studies have often long since passed through the critical "point of no return," at which hybridization will no longer result in fusion of two races (24, 29, 110). They tell us little about how many or what kind of genes are directly implicated in speciation itself. Thus we are still forced to reconstruct events surrounding specia­ tion from observations on extant species, a task that has fallen almost exclusively to the naturalist (see 44, 69, 72, 124 for historical aspects). Speciation is ultimately an adaptive process that involves establishment of intrin­ sic barriers to gene flow between closely related populations by development of reproductive isolating mechanisms. A study of speciation is, to a considerable extent, a study of the genetics and evolution of reproductive isolating mechanisms. Most evolutionists therefore generally accept as a working definition the biological species concept: species represent groups of interbreeding natural populations repro­ ductively isolated from other such groups (125). Although it has its weak points (44), alternatives (e.g. 65, 164) impose more problems than they solve. Selection for reproductive isolation between closely related populations is funda­ mentally different from the process involved in local adaptation (28, 109, 181). The latter entails only minor genetic adjustments, whereas speciation frequently involves a reorganization of some crucial component in the genetic system that results in a

Spectral Analysis in Ecology

Abstract: Ecologists, like other biologists, are involved with the study of living systems, and they, again like other biologists, are handicapped in their work by the inadequacy of the conceptual framework to which they must relate their quantitative results, and within which they must generate new and testable hypotheses. One way in which the weakness of this structure manifests itself is in the lack of a theoretical approach consistently applicable to a wide variety of living systems, and able to lead to powerful predictions of high generality. Various such approaches have been tried and found wanting; for example, the most recent candidate, the systems analysis method, requires colossal labor· and expense to produce a solution that is self­ consistent for a particular data set, but for which is guaranteed neither the unique­ ness in the original data set nor the self-consistency in any other data set that may be drawn from the same system ensemble, regardless of the boundary conditions. In other words, both the predictive power and the generality of this inelegant approach are very low. A new foundation for a theoretical biology has been proposed based on nonlinear statistical mechanics (49). This method, which is neither strictly holism nor wholly reductionism, is emerging from attempts to find a general mathematical approach that would account for living as well as nonliving phenomena. It identifies as the most important characteristic of complex systems the property' that the differential equations describing the functional relationships between the system components be of the nonlinear kind. A crucial characteristic of nonlinear systems is their disposition toward periodic behavior, even for non periodic boundary conditions. Therefore, they tend to a periodic (cyclic) organization in time, in space, or in both. According to this view, the biosystem is seen as an ensemble of nonlinear oscillators, coupled together in various functional configurations at each hierarchic level of system description. The

Ecological Significance of Imprinting and Early Learning

Abstract: Recent years have seen a considerable expansion in the study of imprinting, both in the groups of animals studied and the motivational systems and the kinds of problems involved. Whereas early work on imprinting was restricted almost entirely to birds, some recent investigations have also been carried out with insects, fish, and mammals. And whereas the early findings referred only to the acquisition of object preferences in the social sphere, studies in the meantime have been extended to a wide variety of other behavioral characters (5, 40). Moreover, apart from collecting further data about the various aspects of the phenomenon of imprinting itself, research now also covers the physiological background of the imprinting process, e.g. its possible relationships with the maturation of sensory organs and pathways (8, 74), with brain maturation (49, 86), with biochemical changes in the brain (7, 37, 83), and with the maturation of hormonal systems (50). Finally, it is being realized more and more that imprinting may also be of considerable ecological and evolutionary significance. It is this aspect that has found increasing attention during recent years and that seems to justify a review in a series mainly devoted to the field of ecology.

Late Quaternary Climatic Change in Africa

Abstract: During the past decade, emphasis in ecology has shifted from ecosystem studies to the evolutionary background of natural communities. The community analog of physiology, though far from completely understood, has been supplanted by a community analog of embryology as the most compelling and provocative branch of the subject. This recognition of the systematic and evolutionary complexity of ecological phenomena follows a period during which ecologists sometimes lost sight of the organisms while in pursuit of transferred calories or cycled gcochemicals. By recog­ nizing the complexity of the world we will be in a better position to deal with it realistically. If, at the same time, we can discern some order in the complexity by using or extending evolutionary and genetic theory, so much the better. By adding evolutionary time to the ecological game, however, we generate a need to know things about the natural geography of our planet that are not part of the standard intellectual equipment of biologists. In particular, an accurate under­ standing of the nature, amplitude, and timing of changes in the geographical param­ eters of ecological systems is vital. Some of the fundamental data, such as the rate of movement of tectonic plates, have only recently been established. Facts such as the basic mutability of tropical environments were not taught because they seemed of little importance in biology, even though they have been well known to geogra­ phers and geologists for two generations. Ecologists interested in making effective use of an evolutionary temporal perspective must be alert to ways in which the world has changed, ways in which it is changing now, and ways in which it will change. This review summarizes current knowledge in one branch of natural geography, the late-Quaternary paleoclimatology of Africa. Unlike Darwin, leaders of the new evolutionary movement in ecology have not been especially concerned with environmental change. Most of them were educated in the temperate zone where both the annual march of the seasons and the great Pleistocene climatic changes are expressed vividly. When temperate ecologists go to

The Population Biology of Coral Reef Fishes

Abstract: The development of self-contained underwater breathing apparatus (scuba) has, in the past few decades, provided population biologists with access to the shallow waters of the sea. The availability of scuba has also created an enormous sportdiving industry, with much attention paid to tropical areas. A popular interest in the spectacular fish faunas of coral reefs, analogous to that shown in birds and butterflies, seems to be developing. This interest will have advantages for the professional scientist. Many observations and photographs will be made in field and aquarium by amateurs, and large markets will permit publica­ tion of what otherwise would have been unprofitable literature. For instance, an excellent guide to the common fishes of Caribbean reefs, designed for underwater use, has recently appeared (51). Coral reefs provide diving biologists with a stunning diversity of organisms acces­ sible in three dimensions; a diver is, in a sense, able to do the rough equivalent of flying over, through, and along the edge of a tropical rain forest. Most of the hermatypic (reef-building) corals live in less than 45 m of water (311), a depth that, coincidentally, is almost exactly the maximum recommended by the U.S. Navy for scuba diving with compressed air. Because their symbiotic zooxanthellae require light, no hermatypic corals live below 90 m (31 1), and even that depth is occasion­ ally approached by scuba divers with more courage than good sense. Coral reefs occur through the warm waters of the Indo-Pacific and the western Atlantic (primarily Caribbean) seas. Associated with them to one degree or another are the perhaps 6000-8000 species of fishes that are the subject of this review (41, 59). Scientific work on the biology of reef fishes began relatively recently. Before World War II, pioneering work was done by a few biologists, especially William H. Longley, who used a diving helmet, took pictures of fishes with a camera enclosed in a watertight glass box with front and rear windows of plate glass, and took notes

Ecological aspects of spatial orientation

Abstract: Despite the immense body of literature concerning animal orientation, little previ­ ous effort has been made to prepare a comprehensive discussion and unified theory of orientation ecology, the subdiscipline at the interface between ecology and ethology. Much of the existing orientation literature is widely dispersed, found partially in explicit studies on orientation and partially in countless publications about life histories. In this review, in order to organize this hidden scientific treasure and to facilitate access to it, the concept of orientation ecology is defined, then the subdiscipline is naturally divided into six categories. Finally, within these categories, predictive generalizations or rules, based on induction, deduction, and intuition are formulated. All these rules and principles are preceded by consecutive bold numbers in square brackets to facilitate recognition.

Structure and Climate in Tropical Rain Forest

Abstract: The similarity of tropical rain forests of comparable habitat around the world has struck many observers. This review first discusses similarities in lowland tropical rain forests (lowland forests between the tropics, which in most months receive more rain than they can transpire). Primary concern is with "normal" rain forest, not swamps or heath forest. These forests are also of similar productivity, which reflects an extraordinary similarity of climate, particularly with respect to evaporation: productivity of these forests appears to vary seasonally with transpiration rate. Second, this review discusses montane rain forest, in whose frequently saturated climates structure is often very obviously related to transpiration rate. A marine biologist might well object to treating forest structure without mention­ ing herbivores; therefore, I estimate the impact of vertebrate and insect on fruit and leaf in the old successional forest of Barro Colorado Island, Panama, then explore the rhythms of abundance and scarcity by which tropical forests defend themselves.

Demographic Consequences of Infanticide in Man

Abstract: This monograph represents 15 years of personal experience and research into the medical and anthropological literature of giving birth and breast feeding. Factors which determine success and warn of the path that leads to failure of breast feeding are explained. The period of transition to childbirth for mothers is termed "matrescence." Over 250 cultures were surveyed for their types of ceremonies used during the matrescence transition period. The results indicate that this period is one when support for the mothers well-being is central to her ability to breast feed. The support comes from the "doula" a woman who assists a newly delivered mother by aiding her during the perinatal period. In another study it was found that the incidence of postpartum breakdown increased with the actual distance in miles of the new mother from her own mother sister or close friend. Misconceptions about breast feeding are discussed as well as the physical nature of breast feeding. Advantages and disadvantages of breast feeding are discussed in terms of the relationship between mother and baby initiation of breast milk infection and convenience of breast feeding. Examples of breast feeding adopted babies are emphasized from the authors own experience. From several studies and surveys the common denominater for success in breast feeding is the assurance of some degree of help from some specific person for a definite period of time after childbirth. The use of a "doula" is emphatically emphasized and guidelines are given for their responsibilities and training. Referral services for mothers who are planning to breast feed are listed and discussed as to their value to new mothers.

Simulation Models of Ecosystems

Abstract: Simulations of the kind considered in this review are models of nature, living nature. As'Such, they are subject not only to the physical constraints on flow of matter­ energy, but must conform to the multitudinous constraints required by the many species present in even the simplest of ecosystems. Indeed, it pays the ecological modeler to heed the words quoted above and to use the natural world, if not as teacher, as his guide when resolving questions of model form and function. The results of ignoring this advice are at best useless and at worst positively dangerous, for we live in a world where, more and more, decisions are shaped by the products of science and technology. One of those products that has heralded an exciting new area of ecology research is computer simulation modeling of ecosystems. I propose in this review to outline the origins, structure, and possible future of such models. My dictionary defines simulation as "the act of feigning to be what one is not; the assumption of a deceitful appearance or character." Despite the somewhat pejorative character of this definition, it does describe well enough the modeler's intent, to simplify or substitute a model for the real thing, the ecosystem. But this "simulation model" should reflect the true nature of one or more aspects of reality and should not be a "dissimulation" model, one which, by definition, conceals the truth. In scope, simulation models vary from the detailed but small models of simple thermal communities (108) or microcosms (96) to simulation models of the world (52). A word is needed about the scope of this review. I have deliberately avoided discussion of single population models or of two populations or competition models when these primarily concern predator-prey or competition theory. In the first place, the literature of predation and competition models is too vast an assemblage

The Impact of Robert Macarthur on Ecology

Abstract: Truth is what is-it is the underlying reality of all existence. Knowledge is what we think we know about truth. Knowledge, however, is always an imperfect assess­ ment, and is always subject to revision and improvement. The realization that there are discrepancies and weaknesses in knowledge is wisdom. Wisdom leads to a process, called the philosophy of science, through which knowledge is modified to better fit the truth. Philosophy means the love of wisdom, and doctors of philosophy are supposed, before all else, to be experts in wisdom. Understanding, as defined in Job (28:28), is the effort to avoid evil. We may think of understanding as what we use in order to adequately apply our wisdom and our knowledge in guiding our actions. While applied scientists seek understanding, basic scientists seek knowl­ edge. Dr. Robert MacArthur has made a dramatic impact on ecology because, to him, all of this was second nature.