The ecology and evolution of inducible defenses
01 Sep 1990-The Quarterly Review of Biology (Princeton University Press)-Vol. 65, Iss: 3, pp 323-340
TL;DR: Inducible defenses are responses activated through a previous encounter with a consumer or competitor that confer some degree of resistance to subsequent attacks as discussed by the authors, which can affect the probability of individual survival and growth.
Abstract: Inducible defenses are responses activated through a previous encounter with a consumer or competitor that confer some degree of resistance to subsequent attacks. While the importance of inducible resistance has long been known in host-parasite interactions, it is only recently that its importance has emerged in other natural systems. Althought the structural defenses produced by invertebrates to their competitors and predators are by no means the same as an immune response triggered by parasites, these responses all share the properties of (1) specificity, (2) amplification and (3) memory. This review discusses the following ecological consequences and evolutionary causes of inducible defenses: (1) Inducible defenses render historical factors important in biological interactions and can affect the probability of individual survival and growth, as well as affect population dynamics of consumers in some circumstances. (2) Although the benefits of inducible defenses are often balanced by fitness costs, incl...
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TL;DR: It is concluded that trophic cascades and top-down community regulation as envisioned by trophIC-level theories are relatively uncommon in nature.
Abstract: Food webs in nature have multiple, reticulate connections between a diversity of consumers and resources. Such complexity affects web dynamics: it first spreads the direct effects of consumption and productivity throughout the web rather than focusing them at particular "trophic levels." Second, consumer densities are often donor controlled with food from across the trophic spectrum, the herbivore and detrital channels, other habitats, life-history omnivory, and even trophic mutualism. Although consumers usually do not affect these resources, increased numbers often allow consumers to depress other resources to levels lower than if donor-controlled resources were absent. We propose that such donor-controlled and "multichannel" omnivory is a general feature of consumer control and central to food web dynamics. This observation is contrary to the normal practice of inferring dynamics by simplifying webs into a few linear "trophic levels," as per "green world" theories. Such theories do not accommodate commo...
1,995 citations
TL;DR: It is shown that overexpression ofNMDA receptor 2B (NR2B) in the forebrains of transgenic mice leads to enhanced activation of NMDA receptors, facilitating synaptic potentiation in response to stimulation at 10–100 Hz, suggesting that genetic enhancement of mental and cognitive attributes such as intelligence and memory in mammals is feasible.
Abstract: Hebb's rule (1949) states that learning and memory are based on modifications of synaptic strength among neurons that are simultaneously active. This implies that enhanced synaptic coincidence detection would lead to better learning and memory. If the NMDA (N-methyl-D-aspartate) receptor, a synaptic coincidence detector, acts as a graded switch for memory formation, enhanced signal detection by NMDA receptors should enhance learning and memory. Here we show that overexpression of NMDA receptor 2B (NR2B) in the forebrains of transgenic mice leads to enhanced activation of NMDA receptors, facilitating synaptic potentiation in response to stimulation at 10-100 Hz. These mice exhibit superior ability in learning and memory in various behavioural tasks, showing that NR2B is critical in gating the age-dependent threshold for plasticity and memory formation. NMDA-receptor-dependent modifications of synaptic efficacy, therefore, represent a unifying mechanism for associative learning and memory. Our results suggest that genetic enhancement of mental and cognitive attributes such as intelligence and memory in mammals is feasible.
1,838 citations
TL;DR: A fuller understanding of patterns of human plasticity in response to early nutrition and other environmental factors will have implications for the administration of public health.
Abstract: Many plants and animals are capable of developing in a variety of ways, forming characteristics that are well adapted to the environments in which they are likely to live. In adverse circumstances, for example, small size and slow metabolism can facilitate survival, whereas larger size and more rapid metabolism have advantages for reproductive success when resources are more abundant. Often these characteristics are induced in early life or are even set by cues to which their parents or grandparents were exposed. Individuals developmentally adapted to one environment may, however, be at risk when exposed to another when they are older. The biological evidence may be relevant to the understanding of human development and susceptibility to disease. As the nutritional state of many human mothers has improved around the world, the characteristics of their offspring--such as body size and metabolism--have also changed. Responsiveness to their mothers' condition before birth may generally prepare individuals so that they are best suited to the environment forecast by cues available in early life. Paradoxically, however, rapid improvements in nutrition and other environmental conditions may have damaging effects on the health of those people whose parents and grandparents lived in impoverished conditions. A fuller understanding of patterns of human plasticity in response to early nutrition and other environmental factors will have implications for the administration of public health.
1,568 citations
TL;DR: The case for the broad mechanistic basis for TMIIs is developed and the direct evidence for T MIIs in various permutations of simple three- to four-species food webs is reviewed.
Abstract: In this paper we review the empirical studies documenting trait-mediated indirect interactions (TMIIs) in food webs. Basic models and empirical approaches that form the foundation of our conceptualization of species interactions generally assume that interactions are an intrinsic property of the two interacting species and therefore are governed by their respective densities. However, if a species reacts to the presence of a second species by altering its phenotype, then the trait changes in the reacting species can alter the per capita effect of the reacting species on other species and, consequently, population density or fitness of the other species. Such trait-mediated indirect interactions can reinforce or oppose density-mediated effects and have been largely overlooked by community ecologists. We first briefly develop the case for the broad mechanistic basis for TMIIs and then review the direct evidence for TMIIs in various permutations of simple three- to four-species food webs. We find strong evid...
1,515 citations
TL;DR: Phenotypic responses in species interactions represent modifications that can lead to reciprocal change in ecological time, altered community patterns, and expanded evolutionary potential of species.
Abstract: When individuals of two species interact, they can adjust their phenotypes in response to their respective partner, be they antagonists or mutualists. The reciprocal phenotypic change between individuals of interacting species can reflect an evolutionary response to spatial and temporal variation in species interactions and ecologically result in the structuring of food chains. The evolution of adaptive phenotypic plasticity has led to the success of organisms in novel habitats, and potentially contributes to genetic differentiation and speciation. Taken together, phenotypic responses in species interactions represent modifications that can lead to reciprocal change in ecological time, altered community patterns, and expanded evolutionary potential of species.
1,485 citations
References
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Book•
01 Jan 1981
TL;DR: The genetic constitution of a population: Hardy-Weinberg equilibrium and changes in gene frequency: migration mutation, changes of variance, and heritability are studied.
Abstract: Part 1 Genetic constitution of a population: Hardy-Weinberg equilibrium. Part 2 Changes in gene frequency: migration mutation. Part 3 Small populations - changes in gene frequency under simplified conditions. Part 4 Small populations - less simplified conditions. Part 5 Small populations - pedigreed populations and close inbreeding. Part 6 Continuous variation. Part 7 Values and means. Part 8 Variance. Part 9 Resemblance between relatives. Part 10 Heritability. Part 11 Selection - the response and its prediction. Part 12 Selection - the results of experiments. Part 13 Selection - information from relatives. Part 14 Inbreeding and crossbreeding - changes of mean value. Part 15 Inbreeding and crossbreeding - changes of variance. Part 16 Inbreeding and crossbreeding - applications. Part 17 Scale. Part 18 Threshold characters. Part 19 Correlated characters. Part 20 Metric characters under natural selection.
20,288 citations
Journal Article•
TL;DR: For the next few weeks the course is going to be exploring a field that’s actually older than classical population genetics, although the approach it’ll be taking to it involves the use of population genetic machinery.
Abstract: So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to
9,847 citations
Book•
01 Dec 1982TL;DR: A modification of the theory of games, a branch of mathematics first formulated by Von Neumann and Morgenstern in 1944 for the analysis of human conflicts, was proposed in this paper.
Abstract: I want in this article to trace the history of an idea. It is beginning to become clear that a range of problems in evolution theory can most appropriately be attacked by a modification of the theory of games, a branch of mathematics first formulated by Von Neumann and Morgenstern in 1944 for the analysis of human conflicts. The problems are diverse and include not only the behaviour of animals in contest situations but also some problems in the evolution of genetic mechanisms and in the evolution of ecosystems. It is not, however, sufficient to take over the theory as it has been developed in sociology and apply it to evolution. In sociology, and in economics, it is supposed that each contestant works out by reasoning the best strategy to adopt, assuming that his opponents are equally guided by reason. This leads to the concept of a ‘minimax’ strategy, in which a contestant behaves in such a way as to minimise his losses on the assumption that his opponent behaves so as to maximise them. Clearly, this would not be a valid approach to animal conflicts. A new concept has to be introduced, the concept of an ‘evolutionary stable strategy’.
8,276 citations
TL;DR: Measures of directional and stabilizing selection on each of a set of phenotypically correlated characters are derived, retrospective, based on observed changes in the multivariate distribution of characters within a generation, not on the evolutionary response to selection.
Abstract: Natural selection acts on phenotypes, regardless of their genetic basis, and produces immediate phenotypic effects within a generation that can be measured without recourse to principles of heredity or evolution. In contrast, evolutionary response to selection, the genetic change that occurs from one generation to the next, does depend on genetic variation. Animal and plant breeders routinely distinguish phenotypic selection from evolutionary response to selection (Mayo, 1980; Falconer, 1981). Upon making this critical distinction, emphasized by Haldane (1954), precise methods can be formulated for the measurement of phenotypic natural selection. Correlations between characters seriously complicate the measurement of phenotypic selection, because selection on a particular trait produces not only a direct effect on the distribution of that trait in a population, but also produces indirect effects on the distribution of correlated characters. The problem of character correlations has been largely ignored in current methods for measuring natural selection on quantitative traits. Selection has usually been treated as if it acted only on single characters (e.g., Haldane, 1954; Van Valen, 1965a; O'Donald, 1968, 1970; reviewed by Johnson, 1976 Ch. 7). This is obviously a tremendous oversimplification, since natural selection acts on many characters simultaneously and phenotypic correlations between traits are ubiquitous. In an important but neglected paper, Pearson (1903) showed that multivariate statistics could be used to disentangle the direct and indirect effects of selection to determine which traits in a correlated ensemble are the focus of direct selection. Here we extend and generalize Pearson's major results. The purpose of this paper is to derive measures of directional and stabilizing (or disruptive) selection on each of a set of phenotypically correlated characters. The analysis is retrospective, based on observed changes in the multivariate distribution of characters within a generation, not on the evolutionary response to selection. Nevertheless, the measures we propose have a close connection with equations for evolutionary change. Many other commonly used measures of the intensity of selection (such as selective mortality, change in mean fitness, variance in fitness, or estimates of particular forms of fitness functions) have little predictive value in relation to evolutionary change in quantitative traits. To demonstrate the utility of our approach, we analyze selection on four morphological characters in a population of pentatomid bugs during a brief period of high mortality. We also summarize a multivariate selection analysis on nine morphological characters of house sparrows caught in a severe winter storm, using the classic data of Bumpus (1899). Direct observations and measurements of natural selection serve to clarify one of the major factors of evolution. Critiques of the "adaptationist program" (Lewontin, 1978; Gould and Lewontin, 1979) stress that adaptation and selection are often invoked without strong supporting evidence. We suggest quantitative measurements of selection as the best alternative to the fabrication of adaptive scenarios. Our optimism that measurement can replace rhetorical claims for adaptation and selection is founded in the growing success of field workers in their efforts to measure major components of fitness in natural populations (e.g., Thornhill, 1976; Howard, 1979; Downhower and Brown, 1980; Boag and Grant, 1981; Clutton-Brock et
4,990 citations
Book•
01 Jan 1977TL;DR: In this article, the authors propose a clock model of Heterochrony, which is a mechanism for separating the three stages of the development of an organism: birth, growth, and death.
Abstract: * *1. Prospectus * Part I: Recapitulation *2. The Analogistic Tradition from Anaximander to Bonnet * The Seeds of Recapitulation in Greek Science? * Ontogeny and Phylogeny in the Conflict of "Evolution" and Epigenesis: The Idyll of Charles Bonnet * Appendix: The Revolution in "Evolution" *3. Transcendental Origins, 1793--1860 * Naturphilosophie: An Expression of Developmentalism * Two Leading Recapitulationists among the Naturphilosophen: Oken and Meckel * Oken's Classification of Animals Linear Additions of Organs * J. F. Meckel's Sober Statement of the Same Principles * Serres and the French Transcendentalists * Recapitulation and the Theory of Developmental Arrests * Von Baer's Critique of Recapitulation * The Direction of Development and Classification of Animals * Von Baer and Naturphilosophie: What Is the Universal Direction of Development? * Louis Agassiz and the Threefold Parallelism *4. Evolutionary Triumph, 1859--1900 * Evolutionary Theory and Zoological Practice * Darwin and the Evolution of Von Baer' Laws * Evolution and the Mechanics of Recapitulation * Ernst Haeckel: Phylogeny as the Mechanical Cause of Ontogeny * The Mechanism of Recapitulation * The American Neo-Lamarckians: The Law of Acceleration as Evolution's Motor * Progressive Evolution by Acceleration * The Extent of Parallelism * Why Does Recapitulation Dominate the History of Life? * Alpheus Hyatt and Universal Acceleration * Lamarckism and the Memory Analogy * Recapitulation and Darwinism * Appendix: The Evolutionary Translation of von Baer's Laws *5. Pervasive Influence * Criminal Anthropology * Racism * Child Development * Primary Education * Freudian Psychoanalysis * Epilogue *6. Decline, Fall, and Generalization * A Clever Argument * An Empirical Critique * Organs or Ancestors: The Transformation of Haeckel's Heterochrony * Interpolations into Juvenile Stages * Introduction of Juvenile Features into the Adults of Descendants * What Had Become of von Baer's Critique? * Benign Neglect: Recapitulation and the Rise of Experimental Embryology * The Prior Assumptions of Recapitulation * Wilhelm His and His Physiological Embryology: A Preliminary Skirmish * Roux's Entwicklungsmechanik and the Biogenetic Low * Recapitulation and Substantive Issues in Experimental Embryology: The New Preformationism * Mendel's Resurrection, Haeckel's Fall, and the Generalization of Recapitulation * Part II: Heterocrony and Paedomorphosis *7. Heterochrony and the Parallel of Ontogeny and Phylogeny * Acceleration and Retardation * Confusion in and after Haeckel's Wake * Guidelines for a Resolution * The Reduction of de Beer's Categories of Heterochrony to Acceleration and Retardation * A Historical Paradox: The Supposed Dominance of Recapitulation * Dissociability and Heterochrony * Correlation and Disociability * Dissociation of the Three Processes * A Metric for Dissociation * Temporal Shift as a Mechanism of Dissociation * A Clock Model of Heterochrony * Appendix: A Note on the Multivariate Representation of Dissociation *8. The Ecological and Evolutionary Significance of Heterochrony * The Argument from Frequency * The Importance of Recapitulation * The Importance of Heterochronic Change: Selected Cases * Frequency of Paedomorphosis in the Origin of Higher Taxa * A Critique of the Classical Significance of Heterochrony * The Classical Arguments * Retrospective and Immediate Significance * Heterochrony, Ecology, and Life-History Strategies * The Potential Ease and Rapidity of Heterochronic Change * The Control of Metamorphosis in Insects * Amphibian Paedomorphosis and the Thyroid Gland *9. Progenesis and Neoteny Insect Progenesis * Prothetely and Metathetely * Paedogenesis (Parthenogenetic Progenesis) in Gall Midges and Beetles * Progenesis in Wingless, Parthenogenetic Aphids * Additional Cases of Progenesis with a Similar Ecological Basis * Neotenic Solitary Locusts: Are They an Exception to the Rule? * Amphibian Neoteny * The Ecological Determinants of Progenesis * Unstable Environments * Colonization * Parasites * Male Dispersal * Progenesis as an Adaptive Response to Pressures for Small Size * The Role of Heterochrony in Macroevolution: Contrasting Flexibilities for Progenesis and Neoteny * Progenesis * Neoteny * The Social Correlates of Neoteny in Higher Vertebrates *10. Retardation and Neoteny in Human Evolution * The Seeds of Neoteny * The Fetalization Theory of Louis Bolk * Bolk's Data * Bolk's Interpretation * Bolk's Evolutionary Theory * A Tradition of Argument * Retardation in Human Evolution * Morphology in the Matrix of Retardation * Of Enumeration * Of Prototypes * Of Correlation * The Adaptive Significance of Retarded Development *11. Epilogue * Notes * Bibliography * Glossary * Index
4,117 citations