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Biogeography may be defined simply as the study of the geographical
distribution of organisms, but this simple definition hides the
great complexity of the subject. Biogeography transcends classical
subject areas and involves a range of scientific disciplines that
includes geogra phy, geology and biology. Not surprisingly,
therefore, it means rather different things to different people.
Historically, the study of biogeogra phy has been concentrated into
compartments at separate points along a spatio-temporal gradient.
At one end of the gradient, ecological biogeography is concerned
with ecological processes occurring over short temporal and small
spatial scales, whilst at the other end, historical biogeography is
concerned with evolutionary processes over millions of years on a
large, often global scale. Between these end points lies a third
major compartment concerned with the profound effects of
Pleistocene glaciations and how these have affected the
distribution of recent organisms. Within each of these compartments
along the scale gradient, a large number of theories, hypotheses
and models have been proposed in an attempt to explain the present
and past biotic distribution patterns. To a large extent, these
compartments of the subject have been non-interactive, which is
understandable from the different interests and backgrounds of the
various researchers. Nevertheless, the distribu tions of organisms
across the globe cannot be fully understood without a knowledge of
the full spectrum of ecological and historical processes. There are
no degrees in biogeography and today's biogeographers are primarily
born out of some other discipline."
During the past two decades, there has been a gradual change of
emphasis in ecological studies directed at unravelling the
complexity of natural communities. Initially, the population
approach was used, where interest lay in the way individual
populations change and in the identification of factors af fecting
these changes. A good understanding of the dynamics of single
populations is now emerging, but this has not been a very fruitful
approach at the community level. In the natural world, few species
can be treated as isolated populations, as most single species are
the interacting parts of multispecies systems. This has led to a
community approach, involving the study of interrelationships
between species within com munities and investigation of the actual
organization of natural communities as a whole. The formalization
of a number of new concepts and ideas has evolved from this
approach, including niche theory, resource allocation, guild
structure, limiting similarity, niche width and overlap etc.,
which, until fairly recently, have been examined mainly from a
theoretical point of view. However, a wealth of field data is
gradually being added to the literature, especially from the
general areas of island biogeography and resource partitioning
amongst closely related species. Community structure embodies
patterns of resource allocation and spatial and temporal abundance
of species of the community, as well a. '1 community level
properties such as trophic levels, succession, nutrient cycling
etc."
The challenges that the world's running water systems now face have
never been more numerous or acute; at the same time, these complex
habitats remain absolutely crucial to human wellbeing and future
survival. If rivers can ever be anything like sustainable, ecology
needs to take its place as an equal among the physical sciences
such as hydrology and geomorphology. A real understanding of the
natural history and ecology of running waters must now be brought
even more prominently into river management. The primary purpose of
this textbook is to provide the up-to-date overview that students
and practitioners will require to achieve this aim. The book's
unifying focus is on rivers and streams as ecosystems in which the
particular identity of organisms is not the main emphasis but
rather the processes in which they are involved - specifically
energy flow and the cycling of materials. It builds on the
physicochemical foundations of the habitat templet and explores the
diversity and adaptations of the biota, progressing from the
population and community ecology of organisms and linking them to
ecosystem processes and services in the wider biosphere via the
complexities of species interactions and food webs. These include
water quality and patterns of river discharge, as well as
aesthetics, waste disposal, and environmental health. While the
book is not primarily focused on application per se, each chapter
addresses how humans affect rivers and, in turn, are affected by
them. A final, future-oriented chapter identifies key strategic
areas and sets a roadmap for integrating knowledge of natural
history and ecology into policy and management. The Biology and
Ecology of Streams and Rivers is an accessible text suitable for
both senior undergraduate and graduate students taking courses in
both lotic and general ecology as well as more established
researchers, practitioners, managers, and conservationists
requiring a concise and contemporary overview of running waters.
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