Adaptations of Desert Organisms - Böcker

There are two basic strategies for coping with life in the desert. The first involves withstanding the extreme conditions using behavioural or physiological tactics. The second strategy is to be a migrant and to opportunistically or seasonally move to where the necessary resources are. Nomadism, i.e. the opportunistic and irregular movements from resource-poor to resource-rich patches, is a tactic that birds, with their mobility, can use, and it is explored by W.R.J. Dean in this volume. For many bird species, such movements between habitats or across landscapes to find patches of resources are essential for their continued existence. The relationship between climate, habitat and movements in the avifauna of arid and semi-arid regions and the advantages and disadvantages of a seasonally migratory or opportunistically nomadic lifestyle are elucidated.

Annual desert plant species of unrelated taxa in the Negev Desert of Israel have developed complementary sets of adaptations and survival strategies as ecological equivalents with physiological, morphological and anatomical resemblances, in the various stages of their life cycles. After 40 years of research in hot deserts Yitzchak Gutterman provides a comprehensive treatise of such adaptations and strategies. In doing so he covers the following topics: post-maturation primary seed dormancy, which prevents germination of maturing seeds before the summer; seed dispersal mechanisms with escape or protection strategies; cautious or opportunistic germination strategies; seedling drought tolerance. The day-length is an important factor in regulating flowering as well as the phenotypic plasticity of seed germination which is also affected by maternal factors.

Eeonomie plants range from those that are eommercially utilised by the industrial nations of the world to those that safeguard the survival of hunter-gatherer aboriginal eommunities. In a world of inereasing human and livestock populations, land and environment degradation, species loss and climatic change, it is becoming inerea- singly important to work for the sustainable management of the world's natural resourees. This is especially important for the arid and semi-arid regions where any abuse of the harsh environment is unforgiving. Plant resourees are especially important sinee they proteet the environment, provide habitats for both flora and fauna, and direetly or indireetly provide the resourees for man's survival. An understanding of how plants are adapted to survive is an essential tool for the better management of the environment. Sinee there are over 20000 useful plants in the arid and sem i-arid regions of the world, of which only a relative few have been even partially investigated, the writer makes no apologies for whieh plants have been included or ignored.All the plants mentioned in the introductory ehap- ters marked with an asterisk are diseussed more fully in Chapter 11.

Water is a paramount factor in determining the distribution of species on a global basis. The responses and adaptations of a species to water stress are critical for its success in any environmental niche. The deserts of the Middle East provide an excellent example of the harsh conditions to which plants are subjected.This volume elucidates the adaptations of these plants in order to sustain their life and reproduce to continue their survival. Topics covered include climate aridity and topographic influence on plant life in the deserts, the role of plants in the lives of the Bedouins, the concept of adaptation, its purposes and causes, adaptations that promote increased water uptake and reduction of water output, as well as those which help the plants to tolerate and/or resist the drought, escaping drought and adaptation to desiccation, and the mechanisms by which halophytes can tolerate and/or resist salinity.

This book begins with the physical and biological characterization of the four North American deserts and a description of the primary adaptations of plants to environmental stress. In the following chapters the authors present case studies of key species representing dominant growth forms of the North American deserts, and provide an up-to-date and comprehensive review of the major patterns of adaptations in desert plants. One chapter is devoted to several important exotic plants that have invaded North American deserts. The book ends with a synthesis of the adaptations and resource requirements of North American desert plants. Further, it addresses how desert plants may respond to global climate change.

Arid lands require that organisms inhabiting them be well-adapted to thrive or even just to survive. This book provides a review of the ecological adaptations - be they behavioural, physiological or morphological - of carnivores to arid environments. Following a general introduction into aridity and arid lands in Africa, the major carnivore families are presented. Ecological adaptations of carnivores in arid lands reveal the amplitude and resilience of the ecology of these animals. In setting up conservation measures, the nature and extent of such adaptations are important facets in determining the effective area and degree of heterogeneity required as habitat by a carnivore population so as to produce a viable unit.

Scarcity of water has brought about a number of structural, behavioural, physiological and ecological adaptations in amphibians inhabiting seasonally xeric habitats. This book describes structural and functional adaptations of key organs such as skin, kidneys, bladder, lungs and ovaries. Behavioural responses to high temperatures mainly involve thermoregulation and the selection of optimal temperatures and humidity. Special emphasis is placed on physiological adaptations: water, electrolyte, nitrogen, and thermal balance and their endocrine control are treated in detail. Development and metamorphosis, larval competition for food resources, and reproductive strategies are only a few of the exciting topics in the chapter on ecological aspects.

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.

This book is a basic account of the life cycles and life history strategies of the major groups of desert arthropods. It covers a wide variety of topics including an overview of major adaptations in desert arthropods, characteristic features of deserts, a comprehensive review of life history theory, and a detailed description of embryonic and postembryonic development. The book also provides an in-depth discussion of the life history traits in these animals including development time, growth rates and patterns, age and size at maturity, size and number of offspring, sex ratios, costs associated with reproduction and longevity, and explains how these traits are inextricably connected by various trade-offs including those between current reproduction and survival, current and future reproduction, and between number, size and sex of offspring. Finally, the relationship between behavioral ecology and life history traits is discussed.

There are two basic strategies for coping with life in the desert. The first involves withstanding the extreme conditions using behavioural or physiological tactics. The second strategy is to be a migrant and to opportunistically or seasonally move to where the necessary resources are. Nomadism, i.e. the opportunistic and irregular movements from resource-poor to resource-rich patches, is a tactic that birds, with their mobility, can use, and it is explored by W.R.J. Dean in this volume. For many bird species, such movements between habitats or across landscapes to find patches of resources are essential for their continued existence. The relationship between climate, habitat and movements in the avifauna of arid and semi-arid regions and the advantages and disadvantages of a seasonally migratory or opportunistically nomadic lifestyle are elucidated.

Eeonomie plants range from those that are eommercially utilised by the industrial nations of the world to those that safeguard the survival of hunter-gatherer aboriginal eommunities. In a world of inereasing human and livestock populations, land and environment degradation, species loss and climatic change, it is becoming inerea- singly important to work for the sustainable management of the world's natural resourees. This is especially important for the arid and semi-arid regions where any abuse of the harsh environment is unforgiving. Plant resourees are especially important sinee they proteet the environment, provide habitats for both flora and fauna, and direetly or indireetly provide the resourees for man's survival. An understanding of how plants are adapted to survive is an essential tool for the better management of the environment. Sinee there are over 20000 useful plants in the arid and sem i-arid regions of the world, of which only a relative few have been even partially investigated, the writer makes no apologies for whieh plants have been included or ignored.All the plants mentioned in the introductory ehap- ters marked with an asterisk are diseussed more fully in Chapter 11.

Water is a paramount factor in determining the distribution of species on a global basis. The responses and adaptations of a species to water stress are critical for its success in any environmental niche. The deserts of the Middle East provide an excellent example of the harsh conditions to which plants are subjected.This volume elucidates the adaptations of these plants in order to sustain their life and reproduce to continue their survival. Topics covered include climate aridity and topographic influence on plant life in the deserts, the role of plants in the lives of the Bedouins, the concept of adaptation, its purposes and causes, adaptations that promote increased water uptake and reduction of water output, as well as those which help the plants to tolerate and/or resist the drought, escaping drought and adaptation to desiccation, and the mechanisms by which halophytes can tolerate and/or resist salinity.

Arid lands require that organisms inhabiting them be well-adapted to thrive or even just to survive. This book provides a review of the ecological adaptations - be they behavioural, physiological or morphological - of carnivores to arid environments. Following a general introduction into aridity and arid lands in Africa, the major carnivore families are presented. Ecological adaptations of carnivores in arid lands reveal the amplitude and resilience of the ecology of these animals. In setting up conservation measures, the nature and extent of such adaptations are important facets in determining the effective area and degree of heterogeneity required as habitat by a carnivore population so as to produce a viable unit.

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.

This book is a basic account of the life cycles and life history strategies of the major groups of desert arthropods. It covers a wide variety of topics including an overview of major adaptations in desert arthropods, characteristic features of deserts, a comprehensive review of life history theory, and a detailed description of embryonic and postembryonic development. The book also provides an in-depth discussion of the life history traits in these animals including development time, growth rates and patterns, age and size at maturity, size and number of offspring, sex ratios, costs associated with reproduction and longevity, and explains how these traits are inextricably connected by various trade-offs including those between current reproduction and survival, current and future reproduction, and between number, size and sex of offspring. Finally, the relationship between behavioral ecology and life history traits is discussed.

Annual desert plant species of unrelated taxa in the Negev Desert of Israel have developed complementary sets of adaptations and survival strategies as ecological equivalents with physiological, morphological and anatomical resemblances, in the various stages of their life cycles. After 40 years of research in hot deserts Yitzchak Gutterman provides a comprehensive treatise of such adaptations and strategies. In doing so he covers the following topics: post-maturation primary seed dormancy, which prevents germination of maturing seeds before the summer; seed dispersal mechanisms with escape or protection strategies; cautious or opportunistic germination strategies; seedling drought tolerance. The day-length is an important factor in regulating flowering as well as the phenotypic plasticity of seed germination which is also affected by maternal factors.

This book begins with the physical and biological characterization of the four North American deserts and a description of the primary adaptations of plants to environmental stress. In the following chapters the authors present case studies of key species representing dominant growth forms of the North American deserts, and provide an up-to-date and comprehensive review of the major patterns of adaptations in desert plants. One chapter is devoted to several important exotic plants that have invaded North American deserts. The book ends with a synthesis of the adaptations and resource requirements of North American desert plants. Further, it addresses how desert plants may respond to global climate change.

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.

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.

Birds are not particularly well suited to desert life. Unlike mammals, they are generally active during the day and do not usually go underground to escape the intense desert heat. Among the few types of birds that have successfully invaded the desert ecosystem are the predators. Many species of hawks, owls, roadrunners, vultures, and shrikes survive very well in deserts. What attributes make this group especially suited to desert life? How have they augmented their abilities to cope with the harsh constraints imposed by the desert habitat? These are among the issues explored in this new volume, which brings together much of the current research on adaptations of avian desert predators.

Deserts, whether hot or cold, are considered to be one of the most difficult environments for living systems, lacking the essential free water which ac­ counts for approximately 60-70% of their body mass and more than 98% of their constituent atoms {Macfarlane 1978}. Amongst vertebrates, reptiles are usually thought of as the animals most adapted or suited to such environments because of their diurnal habit, based on a need for external heat, and their ability to survive far from obvious sources of water. This impression is rein­ forced when one examines the composition of vertebrate faunae characteristic of deserts and arid zones: reptiles predominate and they are often the only vertebrates to be found in hyper-arid areas, such as some parts of the Sahara {Monod 1973}. I recently had occasion to examine this assumption carefully, however, and was led inexorably to the conclusion that reptiles represent a particularly successful desert group, not because of their evolution of superior adaptations, but because of their possession of a basic suite of behavioural and physiologi­ cal characteristics that suit them uniquely to this very resource-limited environment {Bradshaw 1986a}. These fundamental reptilian characteristics are: 1. their low rates of metabolism, compared with birds and mammals, which result in extremely low rates of resource utilisation and lead to considerable economy in the handling of water 2.

Scarcity of water has brought about a number of structural, behavioural, physiological and ecological adaptations in amphibians inhabiting seasonally xeric habitats. Special emphasis is placed on physiological adaptations: water, electrolyte, nitrogen, and thermal balance and their endocrine control are treated in detail.

Desert invertebrates live in an environment where resources alternate unpredictably between brief periods of plenty and prolonged scarcity. This book describes the adaptive strategies of desert invertebrates in acquiring energy and sustaining life under such vicissitudes. Some cooperate in foraging; others compete for resources. Some are nomadic and migrate to more favorable sites as conditions change. Others conserve energy by going into a deep dormancy until better conditions return. Still others store food during plenty and retreat underground during less favorable times.The adaptive modes of husbanding scarce energy resources are diverse and lead to an appreciation of the intricate interactions of animals living near their environmental limits.

Based on three decades of field experience in southwest Asia, southern Africa, and the southwest United States, the author summarizes the major adaptations of plants to desert dunes. This integrative study of plant and diaspore morphology, reactive growth, life cycles, and environmental factors explains and predicts plant distribution. Many kinds of dune syndromes, plant case studies and vegetation transects are discussed and illustrated to clarify the significance of adaptations to specific habitat factors. Although the focus is on vascular plants, the development of microbiotic soil crust, its function, and its composition are discussed as well.

The exigencies of life in the desert environment have resulted in the se­ lection of a diversity of adaptations, both morphological and physiologi­ cal, in the flora and fauna. At the same time, many plants and most small animals are able not merely to exist but even to thrive under desert conditions - mainly by avoiding thermal extremes and by the refine­ ment of pre-existing abilities to economise in water. In the same way, the biotic interactions of the flora and fauna of the desert do not involve many new principles. Nevertheless, conditions in arid regions frequently do invoke refinements of the complex interrelations between predators and their prey, parasites and their hosts, as well as between herbivores and the plants upon which they feed. In this book, I shall discuss not only such interactions and their feedback effects, but also community processes and population dynamics in the desert. The physical conditions of the desert that principally affect predators and their prey are its openness and the paucity of cover. This is re­ stricted to scattered plants, occasional rocks, holes, and crevices in the ground. Furthermore, nightfall does not confer relative invisibility, as it does in many other ecobiomes, because of the clarity of the atmosphere. The bright starlight of the desert renders nearby objects visible even to the human eye, while an incandescent moon bathes the empty landscape with a flood of silver light. Consequently, adaptive coloration is func­ tional at all hours of the day and night.

For centuries biologists have been extremely interested in the structure of desert plants as examples of natural selection to harsh environmental conditions. Indeed, desert plants are frequently used as examples in many biology classes and textbooks to illustrate natural selection, but this has led to an unfortunate litany of errors and misconceptions about desert plant adaptations. This new synthesis focuses on plants of lowland tropical and subtropical arid deserts. Readers will be surprised to discover that many features commonly ascribed to desert plants are rareley observed in the most common species. Instead, the typical structural adaptations of nonsucculent warm desert plants are now viewed as ways to maximize photosynthetic rate.

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.

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.

Ecophysiology of Desert Arthropods and Reptiles starts with a new classification of the world's deserts, based upon the type of precipitation and the effect on their faunas of arthropods and reptiles. This is followed by an account of microclimates and the avoidance of environmental extremes. Whereas thermoregulation is primarily behavioural, responses to water shortage are largely physiological. Seasonal activity and phenology are described, adaptations for burrowing, the avoidance of enemies, and defence, are also outlined. A comparative account of interspecific relationships, feeding specializations, and species diversity in the two taxa is described. The purpose of the book is to provide a new and up-to-date analysis that will stimulate further research along these lines.