Mutualisms between animals and plants, such as pollination, seed dispersal and ant-plant protection, are key ecological processes in many ecosystems throughout the world. Like any other ecological interaction, plant-animal mutualisms occur in a community context. Therefore, one-to-one interactions are very rare in nature and the majority of species, both animals and plants, have more than one partner. Recently, studies on mutualistic interactions at the community level have used the "network approach" in order to simplify complex interactions and to determine both the pattern of interaction and the properties of species in networks. In this dissertation, I use network theory combined with long-term field work, phylogenetic and multivariate analysis, species extinctions simulations and experimental manipulation to identify the pattern of interaction in a seed dispersal network, to assess the contribution of particular animal species to network stability and robustness, and to address the extent to which seed dispersal interactions can structure plant communities. To do so, I studied a hyper-diverse seed dispersal network sampled in the Brazilian Pantanal, which includes interactions among plant species from 28 families and seed dispersers, both native and exotic species, from 25 families and 4 taxonomic groups. This study contributes novel information on seed dispersal at the community level, especially because I examined a diverse and relatively complete seed dispersal network, which may provide insights for other diverse systems, especially in the tropics. Besides generating information on the ecology and evolution of plant-animal interactions, this study also shows that not all seed disperser species are equal at the community level; and body size of dispersers seem to be a useful proxy of relative importance for dispersal services. Since contemporary defaunation differentially affects species depending on body size, this work illustrates how human activities, such as hunting, land use and climate change, affect not only taxa, but also crucial processes in which animals of different body size play different roles. This study emphasizes that conservation science needs to look at the conservation of ecological processes driven by species interactions.

This book is about the regeneration of plants from seed under field conditions. It attempts to give a reasonably balanced overview of the many aspects of this broad topic. The first chapter introduces some general ideas about reproduction in plants. Subsequent chapters deal with the early stages in the life of a plant, from ovule to established seedling, in a more or less chronological order. The final chapter shows how the data on regeneration requirements of different species can be used to explain a number of important characteristics of whole plant communities. The study of the ecological aspects of reproduction by seed touches on a range of issues of current interest in biology. A discussion of seed size and number involves a consideration of the concepts of resource allocation, life cycles and strategies. The in teractions between plants and animals seen in pollination, seed dispersal and predation provide excellent material for the study of coevolution. Investigations on regeneration from seed have greatly our understanding of the causes and maintenance of species added to diversity. The reader will find that virtually all the experiments and field observations described in this book are conceptually very simple. Many of them merely required numerous careful measurements.

Fresh concepts in the study of seed dispersal are spurring a host of exciting new questions, new answers to old questions, new methods and approaches, and a reinvigoration of the field.Seed Dispersal: Theory and its Application in a Changing World presents both recent advances and reviews of current knowledge demonstrating the vigour and vibrancy of the field. It provides new perspectives and directions at a time when efforts to meet growing environmental challenges threatening natural systems are of utmost importance.

Now that so many ecosystems face rapid and major environmental change, the ability of species to respond to these changes by dispersing or moving between different patches of habitat can be crucial to ensuring their survival. Understanding dispersal has become key to understanding how populations may persist. Dispersal Ecology and Evolution provides a timely and wide-ranging overview of the fast expanding field of dispersal ecology, incorporating the very latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species, and community levels are considered. Perspectives and insights are offered from the fields of evolution, behavioural ecology, conservation biology, and genetics. Throughout the book theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible - both plant and animal.

In the summer of 1993, twenty-six graduate and postdoctoral stu dents and fourteen lecturers converged on Cornell University for a summer school devoted to structured-population models. This school was one of a series to address concepts cutting across the traditional boundaries separating terrestrial, marine, and freshwa ter ecology. Earlier schools resulted in the books Patch Dynamics (S. A. Levin, T. M. Powell & J. H. Steele, eds., Springer-Verlag, Berlin, 1993) and Ecological Time Series (T. M. Powell & J. H. Steele, eds., Chapman and Hall, New York, 1995); a book on food webs is in preparation. Models of population structure (differences among individuals due to age, size, developmental stage, spatial location, or genotype) have an important place in studies of all three kinds of ecosystem. In choosing the participants and lecturers for the school, we se lected for diversity-biologists who knew some mathematics and mathematicians who knew some biology, field biologists sobered by encounters with messy data and theoreticians intoxicated by the elegance of the underlying mathematics, people concerned with long-term evolutionary problems and people concerned with the acute crises of conservation biology. For four weeks, these perspec tives swirled in discussions that started in the lecture hall and carried on into the sweltering Ithaca night. Diversity mayor may not increase stability, but it surely makes things interesting.

Any scientific discipline needs a theoretical framework to guide its development and to sharpen the questions its researchers pursue. In biology, evolution is the grand theoretical framework, and an his torical perspective is necessary to understand present-day biological conditions. In its formative years, the modern study of the fruit-frugivore mutualism was guided by the 'specialist-generalist' paradigm developed by D. Snow, D. McKey, and H. Howe. Howe reviews the current status of this evolution ary paradigm and points out that it has been dismissed by many workers before being adequately tested. This is because ecologists working with the tropical plants and frugivorous birds for which the paradigm was originally developed rarely measure the seed dispersal effectiveness of different disperser species. He indicates that this paradigm still has heuristic value and suggests that several additional ecological paradigms, including the concept ofkeystone species ofplants and frugivores and the role that frugivores play in density-dependent mortality in tropical trees, are worth studying. The concept of seed dispersal quality has been central to discussions of fruit-frugivore coevolution. Schupp thoroughly reviews data bearing on this concept, constructs a hierarchical framework for viewing disperser effectiveness, and points out that disperser effectiveness depends on both the quantity and quality of seed dispersal. Effectiveness, in turn, affects both evolutionary and ecological relationships between dispersers and their food plants.

For over one hundred years, ornithologists and amateur birders have jointly campaigned for the conservation of bird species, documenting not only birds’ beauty and extraordinary diversity, but also their importance to ecosystems worldwide. But while these avian enthusiasts have noted that birds eat fruit, carrion, and pests; spread seed and fertilizer; and pollinate plants, among other services, they have rarely asked what birds are worth in economic terms. In Why Birds Matter, an international collection of ornithologists, botanists, ecologists, conservation biologists, and environmental economists seeks to quantify avian ecosystem services—the myriad benefits that birds provide to humans. The first book to approach ecosystem services from an ornithological perspective, Why Birds Matter asks what economic value we can ascribe to those services, if any, and how this value should inform conservation. Chapters explore the role of birds in such important ecological dynamics as scavenging, nutrient cycling, food chains, and plant-animal interactions—all seen through the lens of human well-being—to show that quantifying avian ecosystem services is crucial when formulating contemporary conservation strategies. Both elucidating challenges and providing examples of specific ecosystem valuations and guidance for calculation, the contributors propose that in order to advance avian conservation, we need to appeal not only to hearts and minds, but also to wallets.