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Demography relates observable facts about individuals to the dynamics of populations. If the dynamics are linear and do not change over time, the classical theory of Lotka (1907) and Leslie (1945) is the central tool of demography. This book addresses the situation when the assumption of constancy is dropped. In many practical situations, a population will display unpredictable variation over time in its vital rates, which must then be described in statistical terms. Most of this book is concerned with the theory of populations which are subject to random temporal changes in their vital rates, although other kinds of variation (e. g. , cyclical) are also dealt with. The central questions are: how does temporal variation work its way into a population's future, and how does it affect our interpretation of a population's past. The results here are directed at demographers of humans and at popula tion biologists. The uneven mathematical level is dictated by the material, but the book should be accessible to readers interested in population the ory. (Readers looking for background or prerequisites will find much of it in Hal Caswell's Matrix population models: construction, analysis, and in terpretation (Sinauer 1989) ). This book is in essence a progress report and is deliberately brief; I hope that it is not mystifying. I have not attempted to be complete about either the history or the subject, although most sig nificant results and methods are presented.
Populations living in natural environments experience fluctuations in environmental conditions that drive variability in demographic rates. This dissertation develops new and existing mathematical methods for studying environmental stochasticity and uses these tools to investigate the role of environmental stochasticity in driving observed population dynamics and plant life history evolution. In the first two chapters I develop new approaches to a classic method in population biology, the life table response experiment (LTRE). Whereas existing methods used time-averaged demographic rates and deterministic sensitivities to decompose observed differences in population growth rates, this new method allows estimation of the contributions to those differences made by variances in demographic rates as well as by mean rate values. I use this stochastic LTRE to show how differential variability in the vital rates of Anthyllis vulneraria (kidney vetch) contribute to differences in the population growth rates of nine populations growing in southwest Belgium; we also show how the effects of demographic rate variability depend on soil depth, where the greater moisture retention of deeper soils buffers populations against the otherwise negative effects of demographic variability. The second chapter provides a different approach to LTRE that uses an iterated two-factor decomposition of the small noise approximation of the stochastic population growth rate to quantify contributions to that growth rate made by: (i) mean vital rates, (ii) temporal variability in vital rates, (iii) elasticities of the population growth rate to individual vital rates, and (iv) correlations between vital rates across the study period. Contributions of elasticities tell us about differences in local selection pressures acting on distinct populations and contributions of correlations tell us about differences in the phenotypic tradeoffs associated with vital rates. I use this new method to show how these differences drive dynamics in two species: Anthyllis vulneraria (the same populations studied in the first chapter) and Cypripedium calceolus (lady's slipper orchid). In Anthyllis vulneraria, variability in large adult fertility and seedling survival made the largest contributions; there were also effects of differences in elasticities of large adult fertility and survival, as well as differences in the correlations between rapid growth and survival in seedlings (a survival cost of rapid early development), between large adult fertility and survival (a survival cost of reproduction) and between large adult fertility and seedling survival. In Cypripedium calceolus, population growth rates were driven most by differences in the elasticities to the probabilities of adult stasis vs. entering dormancy, as well as by differences in the variability and tradeoffs associated with adult dormancy; correlation played a role through differences in the survival payoff of dormancy vs. the complimentary fertility cost of dormancy in terms of lost opportunity for reproduction. The third and final chapter investigates the role of fire disturbance in driving the life histories and population-level dynamics of five woody plant species growing in the Brazilian cerrado, a savannah-forest mosaic in which woody vegetation cover is primarily mediated by fire disturbance. This study presents a set of diagnostics that use demographic responses to recurring disturbance to categorize species along a continuum of adaptation: on one end we find 'resistant' species that must weather disturbance in order to attain large sizes that are buffered against fire-induced mortality; on the other end we find 'resilient' species that are relatively indifferent to disturbance and harness transient opportunities afforded by early post-fire successional habitats in order to take advantage of increased nutrient availability and reduced competition. Each of these chapters uses stochastic demographic analysis to extend theory describing the dynamics of populations in variable environments; together, these studies present a variegated perspective on the role of environmental stochasticity that provides new methods and novel perspectives that should be useful in the study of population biology and life history evolution.
This book outlines concepts such as population variability, population stability, population viability and persistance, and harvest yield. Also addressed are specific applications to conservation such as managing species at risk, fishery management, and the spatial manageement of marine resources.--Adapted from back cover.
Dr. Timothy Schowalter has succeeded in creating a unique, updated treatment of insect ecology. This revised and expanded text looks at how insects adapt to environmental conditions while maintaining the ability to substantially alter their environment. It covers a range of topics- from individual insects that respond to local changes in the environment and affect resource distribution, to entire insect communities that have the capacity to modify ecosystem conditions.Insect Ecology, Second Edition, synthesizes the latest research in the field and has been produced in full color throughout. It is ideal for students in both entomology and ecology-focused programs. NEW TO THIS EDITION:* New topics such as elemental defense by plants, chaotic models, molecular methods to measure disperson, food web relationships, and more* Expanded sections on plant defenses, insect learning, evolutionary tradeoffs, conservation biology and more* Includes more than 350 new references* More than 40 new full-color figures