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I have spent less time in the arid zone in the last few years than I did during the 1960's, 1970's and early 1980's. This results from a progression through age and a career structure which gradually shifted the emphasis of my work from being essentially field-oriented to essentially office-hound. When, therefore, I was asked by John Cloudsley-Thompson to undertake the writing of this hook I hesitated for two reasons. One reason was that, although I now had access to good library facilities and kept up with the literature on the arid zones and their fauna, I was not sure that a sedentary and pleasant life in a temperate highland island in tropieal Africa would provide a mental attitude suitable to writing a hook which related to areas where life is usually nomadie and often extremely disagreeable. The other reason was that I was uncertain whether I could devote the time necessary to researehing and writing the hook on top of my professional (which now specifical ly excluded research in the arid zones and on camels) and social (new-found and time-consuming) commitments. In the event I accepted and the fates were kind to me. By some peculiar combination of circumstances I was given the opportunity to spend a considerable part of the first half of 1988 in some of the driest areas of the globe. I had already visited all of the locations used for the construction of Fig. 2.
Abstract Biological vision is a rather fascinating domain of research. Scientists of various origins like biology, medicine, neurophysiology, engineering, math ematics, etc. aim to understand the processes leading to visual perception process and at reproducing such systems. Understanding the environment is most of the time done through visual perception which appears to be one of the most fundamental sensory abilities in humans and therefore a significant amount of research effort has been dedicated towards modelling and repro ducing human visual abilities. Mathematical methods play a central role in this endeavour. Introduction David Marr's theory v^as a pioneering step tov^ards understanding visual percep tion. In his view human vision was based on a complete surface reconstruction of the environment that was then used to address visual subtasks. This approach was proven to be insufficient by neuro-biologists and complementary ideas from statistical pattern recognition and artificial intelligence were introduced to bet ter address the visual perception problem. In this framework visual perception is represented by a set of actions and rules connecting these actions. The emerg ing concept of active vision consists of a selective visual perception paradigm that is basically equivalent to recovering from the environment the minimal piece information required to address a particular task of interest.
In the Preface to his volume on Ecophysiology of the Camelidae and Desert Ruminants in this series, Trevor Wilson mentions his hesitation at the invitation from John Cloudsley-Thompson to write the book, because he had been out of direct touch with desert biology for some years. My response to John's invitation to write Ecophysiology of Desert Birds was much the same, and for the same reasons. However, with his encouragement and, taking account of the fact that a colleague of mine who is much better suited to do the job had turned it down because of pressure of work, I accepted the challenge and have enjoyed it immensely. It has been my privilege to spend much time in the deserts of North and South America, southern Africa and Australia, some of it with my wife, Cherie, whose editing of the entire text has improved the work immeasurably. Indeed, I believe it would have been proper for her to accept coauthorship, but she graciously declined the offer! I owe her a debt of gratitude which I hope will be repaid in part by her seeing the text finally between covers. The chapters on water regulation (Chap. 5) and thermo regulation (Chap. 6) have benefited from the refereeing of my colleague, Dr. Barry Lovegrove, of the Department of Zoology and Entomology, University of Natal, Pietermaritzburg.
Since small mammals have a large surface to mass ratio, one would expect them to quickly dehydrate and perish at high environmental temperatures. Nonetheless, a large number of small mammal species inhabit deserts. This fascinating phenomenon is investigated by Prof. A. Allan Degen in his book. The majority of small desert mammals are rodents, but shrews of several grams and small foxes of 1 kg are also present. Their survival is due mainly to behavioural adaptations and habitat selection, however, physiological adaptations also contribute to the success. Interestingly, many small mammals that live in different deserts of the world show similarities in their adaptive traits although they have different taxonomic affinities.
Following a description of the physical and biological characterization of the four North American deserts together with the primary adaptations of plants to environmental stress, the authors go on to present case studies of key species. They provide an up-to-date and comprehensive review of the major patterns of adaptation in desert plants, with one chapter devoted to several important exotic plants that have invaded these deserts. The whole is rounded off with a synthesis of the resource requirements of desert plants and how they may respond to global climate change.
A description of the structural and functional adaptations of the key organs such as skin, kidneys, bladder, lungs and ovaries, with special emphasis placed on physiological adaptations: water, electrolyte, nitrogen, and thermal balance and their endocrine control. One whole chapter devoted to ecological aspects covers such exciting topics as development and metamorphosis, larval competition for food resources, and reproductive strategies.
This book deals with arid and semi-arid environments and their classification, and the physiological restraints and adaptations of plants to the environment. Further, it discusses economic botany and the needs and methods of conserving economic plants. A broad view is taken regarding the definition of economic plants, taking into account their value to the environment as well as to man and to livestock. The individual deserts and associated semi-arid regions are described in separate chapters, providing background information on the regional environments in terms of climate and major plant formations. The economic plants within these formations, their usages, geographical distribution together with their morphological and physiological adaptations are treated in detail.
After a brief survey of biotopic and vegetational features and an account of the main groups of desert animals, the most unusual patterns of the behaviour of the xerophilous fauna are examined. The importance of the thermohygric regulation and self-protective and locomotor mechanisms to the survival of arid-adapted animals is emphasized and various adaptations in the alimentary, reproductive and social spheres are analyzed. The clear and fluent treatment will awaken the interest of the reading public, from the amateur naturalists to research scientists.
Rodents are conspicuous and important components of the desert biome. Many general concepts in modern community and behavioral ecology use them as a main model. This volume compiles and generalizes data on the spatial structure of desert rodent communities, taking into account both global (biogeographic) and local (ecological) patterns. It is based on studies of rodents in different deserts of the Northern Hemisphere (Karakum, Kyzylkum, Bet-Pak-Dala, Gobi, Thar, Chihuahua, Negev, and North Caspian deserts) as well as on a thorough analysis of the literature.
Dispersal processes have important effects on plant distribution and abundance. Although adaptations to long range dispersal (telechory) are by no means rare in desert plants, many desert plant species do not possess any features to promote dispersal (atelechory), while others have structures that hamper dispersal (antitelechory). The high frequency with which atelechorous and antitelechorous mechanisms are present in plants inhabiting arid areas indicates the importance of these adaptations. Among the benefits derived from these adaptations are the spreading of germination over time, the provision of suitable conditions for germination and subsequent seedling establishment, and the maintenance of a reservoir of available seeds (seed bank). This book describes the ways and means - anatomical, morphological and ecological - by which dispersal in desert plants has evolved to ensure the survival of these species in their harsh and unpredictable environment.