Showing papers in "The Quarterly Review of Biology in 1983"

Sexual selection, social competition, and speciation

Abstract: Rapid divergence and speciation can occur between populations with or without ecological differences under selection for success in intraspecific social competition-competition in which an individual must win in contests or comparisons with conspecific rivals in order to gain access to some resource, including (under sexual selection) mates. Sexual selection theory is extended to encompass social competition for resources other than mates. Characters used in social competition can undergo particularly rapid and divergent evolution owing to (1) their great importance in determining access to critical resources, (2) the absence of a limit to change (except by selection in other contexts), (3) the generation-to-generation relentlessness of selection on these traits. (4) the potential for mutually accelerating evolution of preference and attractiveness in contests involving "choice," and (5) the very large number of factors that can initiate trends, including mutation and drift leading to use of different phy...

The Genesis of Neural Crest and Epidermal Placodes: A Reinterpretation of Vertebrate Origins

Abstract: Vertebrate body organization differs from that of other chordates in a large number of derived features that involve all organ systems. Most of these features arise embryonically from epidermal placodes, neural crest, and a muscularized hypomere. The developmental modifications were associated with a shift from filter-feeding to more active predation, which established advantages for improved gas exchange and distribution. Active predation involved more efficient patterns of locomotion and led to a major reorganization of the pharynx, to elaboration of the circulatory, digestive, and nervous systems, and to special sense organs. Most of the organs that derive from epidermal placodes and neural crest may have arisen phylogenetically from the epidermal nerve plexus of earlier chordates. Supportive tissues such as cartilage, bone, dentine, and enamel-like tissues probably arose in association with several of the new vertebrate sense organs and only secondarily provided mechanical support. The development of ...

Reproductive Suppression Among Female Mammals: Implications for Biomedicine and Sexual Selection Theory

Abstract: Female mammals experience a very high and often unappreciated rate of reproductive failure. Among human pregnancies alone, over 50 per cent fail between conception and parturition, and the majority of these failures are unexplained. These findings present important problems for evolutionary theory as well as for health care practices. This paper addresses these high rates of reproductive failure among mammals, by extending the work of a number of evolutionary biologists regarding the reproductive consequences of environmental adversity. The basic model upon which we elaborate, termed the Reproductive Suppression Model, argues that females can optimize their lifetime reproductive success by suppressing reproduction when future conditions for the survival of offspring are likely to be sufficiently better than present ones as to exceed the costs of the suppression itself. These costs are a function of reproductive time lost and the direct phenotypic effects of the suppression itself. To evaluate the benefits...

Natal philopatry among solitary mammals

Abstract: Although many studies treat the causes and consequences of dispersal in mammalian populations, less attention has been given to the individuals that do not leave their birthplaces. Yet natal philopatry, which we define as continued residence on the natal home range past the age of independence from the parents, occurs in virtually all gregarious mammals. We here document its widespread occurrence among solitary species as well. By studying the distribution of natal philopatry across various ecological and life-history regimes we attempt to identify its ultimate causes. The variables that emerge as possibly important include adult turnover rates, habitat saturation, spatial patchiness of resources, advantages of familiarity with the natal home range, and reliance on extensive home range "improvements" such as burrow systems of food caches. The most interesting consequence of natal philopatry is the continued spatial association of kin into adulthood, a prerequisite for many phenomena common to gregarious s...

Energy metabolism, brain size and longevity in mammals.

Abstract: The mathematical relations between basal energy metabolism, brain size, and life span in mammals have been investigated. The evolutionary level of brain development, or encephalization (c), is a function both of brain weight (E) and of body weight (P) according to c = E/P0.732. Brain weight was found to be a linear function of the product of encephalization and basal metabolic rate. The oxygen consumption of the brain (Mbrain) is proportional to both encephalization and body weight according to Mbrain∞ cP0.59. The ratio of metabolic rate in the cerebral cortex to that in the brain as a whole depends solely upon the degree of encephalization and is independent of the size of the animal. The maximum potential life span of a mammal was found to be proportional to the product of its degree of encephalization and the reciprocal of its metabolic rate per unit weight. Life span may be regarded as the algebraic sum of two components: (1) a deduced somatic component (Lb) inversely related to the basal metabolic ra...

Dinosaur Success in the Triassic: A Noncompetitive Ecological Model

Abstract: The initial radiation of the dinosaurs in the Triassic period (about 200 million years ago) has been generally regarded as a result of successful competition with the previously dominant mammal-like reptiles. A detailed review of major terrestrial reptile faunas of the Permo-Triassic, including estimates of relative abundance, gives a different picture of the pattern of faunal replacements. Dinosaurs only appeared as dominant faunal elements in the latest Triassic after the disappearance of several groups of mammal-like reptiles, thecondontians (ancestors of dinosaurs and other archosaurs), and rhynchosaurs (medium-sized herbivores). The concepts of differential survival ("competitive") and opportunistic ecological replacement of higher taxonomic categories are contrasted (the latter involves chance radiation to fill adaptive zones that are already empty), and they are applied to the fossil record. There is no evidence that either thecodontians or dinosaur demonstrated their superiority over mammal-like r...

Somatic Incompatibility in the Development of Higher Plant Somatic Hybrids

Abstract: The fusion of somatic cells offers unique prospects for combining plant species that cannot be crossed sexually. This review investigates the involvement and consequences for intergeneric somatic hybridization of various types of somatic incompatibility as a phenomenon analogous to incompatibility and incongruity in sexual crosses. From an extensive survey of the literature on plant as well as vertebrate somatic cell fusion, various intracellular processes have been identified and are discussed as operational sites for somatic incompatibility reactions that interfere with the regular development of somatic hybrid cells and plants. The structural and dynamic instability of chromosomes can explain why many intergeneric fusion products have failed to proliferate continuously. The great complexity of the processes involved in the morphological differentiation of a hybrid plant makes heavy demands on the timing and sychronization of regulatory signals, and thus provides sites of action for somatic incompatibil...

The Darwinian Dynamic

Abstract: We argue that the evolution of order in living systems and certain nonliving physical systems obeys a common fundamental principle which we call the Darwinian dynamic. Such ordered systems deviate greatly from the thermodynamic equiprobability rule according to which, for example, all nucleotide sequences of comparable length should be found in roughly equal abundance. We formulate the Darwinian dynamic by first considering how macroscopic order is generated in a simple nonbiological system far from the thermodynamic equilibrium. We then extend our consideration to short, replicating RNA molecules, which we assume to be like the earliest forms of life, and show that the underlying order-generating process is basically similar. The equation we use as an example of the Darwinian dynamic for these simple replicators contains variables that express the basic conditions necessary for the process of natural selection as conceived by Darwin: variation of type, heritability, and competition for limited resources....

Why is Culture Adaptive

Abstract: W HY IS culture adaptive? One of the 14 Tdistinctive features of the human species is the extent to which behavior is acquired by teaching and imitation. The rapid radiation of the human species into a large variety of ecological niches over a wide geographical range during the last 100,000 years suggests that this mode of adaptation may be quite effective. Until recently, however, few evolutionary biologists have attempted to identify the properties of cultural transmission that make it an effective way of acquiring behavior. Very different answers to this question have been suggested by Charles Lumsden and E. 0. Wilson in Genes, Mind, and Culture (Harvard Univ. Press, 1981) and by H. R. Pulliam and Christopher Dunford in Programmed to Learn (Columbia Univ. Press, 1980). In both of these books, culture is conceptualized in a similar way. Culture is a system of social learning. Skills or attitudes are acquired from conspecifics by teaching or imitation. Culture is therefore a system of inheritance analogous in some ways to genetic inheritance. Unlike genes, cultural transmission is coupled to ordinary learning. Variants invented or modified by one individual can be communicated to others. From this common view of culture, however, the authors develop quite divergent explanations for why culture is adaptive. Although Genes, Mind, and Culture represents a much longer and more ambitious treatment of the role of culture in human evolution than does Programmed to Learn, Pulliam and Dunford appear to present a more interesting and plausible explanation of why culture is adpative than do Lumsden and Wilson. Each of the two views is examined below in more detail.

Progress in Nucleic Acid Research and Molecular Biology. Volume 26 (DNA: Multiprotein Interactions).Waldo E. CohnMolecular Approaches to Gene Expression and Protein Structure.M. A. Q. Siddiqui , Manuel Krauskopf , Herbert Weissbach

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The Evolution of Sex

Abstract: result in a set of completely concordant characters. That, however, would be the compatibility method. Elsewhere, in his Fig. 5.12b, Wiley makes use, in one part of the phylogeny, of a character state that is not uniquely derived, a parsimony approach. The suspicion that there is a muddle here is not helped by Wiley's cavalier dismissal of compatibility methods in one paragraph, partly on the grounds that George Estabrook, one of their developers, has advocated the use of paraphyletic groups in classification and thus is not a good Hennigian. At another point, Wiley gives mistaken definitions for Type I and Type II statistical errors. At another he falls into the trap of giving a detailed blow-by-blow description of one particular, and very approximate, parsimony algorithm, without ever clearly explaining to the reader what it is that the algorithm is trying to do, namely, to find the tree that minimizes the number of character state changes that need have occurred. I think that these problems have a source that goes beyond individual shortcomings of the book or of its author. The Hennigian arguments are usually stated in a terminology of deduction rather than of inference, with terms such as "refutation," "rejection," and "falsification." Much of the appeal of the Hennigian position seems associated with the aura of certainty that these terms convey, and with the appeal to working biologists of a method that can be used without the need for numbers or algorithms. This deterministic framework is, however, imposed on a highly stochastic world. Actual data cannot be analyzed effectively without appealing to criteria external to the Hennigian system, of which parsimony is one. To avoid disrupting the original Hennigian (and Popperian) logical structure, these numerical methods must be grafted onto it in rather strange ways. The pathway from William of Ockham to the "parsimony" method is far more tortuous than first appears. The conflict between a qualitative framework and quantitative methods is the source of much of the trouble. It can be seen in this book, as elsewhere in Hennigian practice, in the failure to make the statistical notions of hypothesis testing and of Type I and Type II errors concrete and practical. Elsewhere in Hennigian practice it takes the form of a strong emphasis on finding the most parsimonious tree, while no emphasis at all is laid on finding out how large are the confidence limits around that estimate. The clarity of this book arises from the strengths of the Hennigian school an intention to convey phylogenetic information clearly, and an insistence on precision and explicitness. Its limitations may to some extent be particular to the author, but must also be those of the Hennigian school -scholasticism and an attempt to impose a rigid, inflexible, and deterministic scheme on a nature in flux, a nature in which pattern cannot be properly inferred without taking process into account. Wiley's book, together with Eldredge and Cracraft's, are beacons, lighting the way out of the fog of inexplicit and intuitive methods, but revealing all too clearly that the path does not lead much farther, and that a different way must be taken.