Showing papers in "The Quarterly Review of Biology in 1977"

Optimal foraging: A selective review of theory and tests

Abstract: Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patch...

Monogamy in mammals

Abstract: This review considers the behavioral, ecological, and reproductive characteristics of mammals exhibiting monogamy, i.e., mating exclusivity. From a discussion of the life histories of selected species of monogamous primates, carnivores, rodents and ungulates, several trends emerge. Two forms of monogamy occur, Type I, facultative, and Type II, obligate. The selective pressures leading to these two forms of monogamy may have been different. Facultative monogamy may result when a species exists at very low densities, with males and females being so spaced that only a single member of the opposite sex is available for mating. Obligate monogamy appears to occur when a solitary female cannot rear a litter without aid from conspecifics, but the carrying capacity of the habitat is insufficient to allow more than one female to breed simultaneously within the same home range. Within both types of monogamy, the following traits are typically seen: (1) adults show little sexual dimorphism either physically or behaviorally: (2) the adult male and female exhibit infrequent socio-sexual interactions except during the early stages of pair bond formation. Additional trends specific to mammals exhibiting obligate monogamy are: (1) the young exhibit delayed sexual maturation in the presence of the parents, and thus only the adult pair breeds; (2) the older juveniles aid in rearing young siblings; and (3) the adult male (father) aids in the rearing of young by any or all of the following: carrying, feeding, defending, and socializing offspring.

An evaluation of narrow hybrid zones in vertebrates

Abstract: A review of the literature on vertebrate hybridization reveals the existence of a number of narrow hybrid zones. Three hypotheses have been suggested to explain the occurrence of these zones. The ephemeral-zone hypothesis states that hybridization will end either in speciation or fusion of the hybridizing taxa by means of introgression. The dynamic-equilibrium hypothesis allows the possibility that narrow hybrid zones might be stable: where hybrids are confined to a small area by steep selection gradients, "crystalization" of an antihybridization mechanism might be prevented by naive immigrants from the parental populations eve though hybrids are selected against. The hybrid-superiority hypothesis states that hybrids are more fit than parental phenotypes in some environments. The ephemeral-zone hypothesis fails to explain the antiquity and apparent stability of several hybrid zones. The dynamic-equilibrium hypothesis does not adequately explain the persistence of hybrid populations that do not receive a s...

A Systems-Analytical Approach to Macro-Evolutionary Phenomena

Abstract: Two sets of evolutionary phenomena find no explanation through current theory. for the static pehnomena (such as homology, homonomy, sistematic weight, and 'Type') there is no causal base, although...

The Biological Effects and Mode of Action of L-Canavanine, a Structural Analogue of L-Arginine

Abstract: Many of the 200 or so non-protein amino acids synthesized by higher plants are related structurally to the constituents of common proteins. L-Canavanine, the guanidinooxy structural analogue of L-arginine, is representative of this group. It has provided valuable insight into the biological effects and the mode of action of non-protein amino acids which acts as analogues of the protein amino acids. The arginyl-tRNA synthetases of numerous canavanine-free species charge canavanine, and canavanine is subsequently incorporated into the nascent polypeptide chain. Production of canavanine-containing proteins ultimately can disrupt critical reactions of RNA and DNA metabolism as well as protein synthesis. Canavanine also affects regulatory and catalytic reactions of arginine metabolism, arginine uptake, formation of structural components, and other cellular precesses. In these ways, canavanine alters essential biochemical reactions and becomes a potent antimetabolite of arginine in a wide spectrum of species. These deleterious properties of canavanine render it a highly toxic secondary plant constituent that probably functions as an allelochemic agent that deters the feeding activity of phytophagous insects and other herbivores.

On Territoriality in Ungulates and an Evolutionary Model

Abstract: The behavioral characteristics of territorial ungulates are reviewed and compared with non-territorial species in terms of social distribution, spatial dispersion, and interaction patterns. Territoriality is related proximally to dominance and ultimately to mating exhancement. Alternative male mating strategies are categorized. Selective gains are estimated by the potential mating enhancement factor (PMEF) and costs by reduced chances of survival. The likely lifetime mating enhancement (LLME) resulting from territorial versus roving/rank dominance strategies are calculated for model populations. Ecological conditions favoring territoriality are discussed, and a comparison is made with territorial systems in other animal groups. There is a need for more empirical data.

Aspects of Biological Exploitation

Abstract: The population interaction termed biological exploitation includes what has formely been called predation, as well as other interactions in which one population takes advantage of another (e.g., grazing, parasitism, batesian Mimicry). An instantaneous, deterministic theory using graps of the properties of difficult and even unknown autonomous nonlinear differential equation systems has been developed to simplify greatly the task of understanding the dynamics of such systems and of predicting qualitative properties of their solutions. This review shows how the theory may be used to account for some of the observed dynamics of well-known laboratory sistems including their oscillatory periods and neighborhood stability. It also extends the theory to cover situations where the predator prefers to attack weak or otherwise vulnerable victims, In this case, an upper limit is shown to be added to victim oscillations which can serve to promote the survival probability of the system despite the fact that it may dim...