The long-awaited fourth edition of a classic text, now fully revised and updated for the molecular era.

Considers how the study of variation in plants has developed over the last 300 years.

"The present book is intended as a progress report on [the] synthetic approach to evolution as it applies to the plant kingdom." With this simple statement, G. Ledyard Stebbins formulated the objectives of Variation and Evolution in Plants, published in 1950, setting forth for plants what became known as the "synthetic theory of evolution" or "the modern synthesis." The pervading conceit of the book was the molding of Darwin's evolution by natural selection within the framework of rapidly advancing genetic knowledge. At the time, Variation and Evolution in Plants significantly extended the scope of the science of plants. Plants, with their unique genetic, physiological, and evolutionary features, had all but been left completely out of the synthesis until that point. Fifty years later, the National Academy of Sciences convened a colloquium to update the advances made by Stebbins. This collection of 17 papers marks the 50th anniversary of the publication of Stebbins' classic. Organized into five sections, the book covers: early evolution and the origin of cells, virus and bacterial models, protoctist models, population variation, and trends and patterns in plant evolution.

We are in the midst of a biological revolution. Molecular tools are now providing new means of critically testing hypotheses and models of microevolution in populations of wild, cultivated, weedy and feral plants. They are also offering the opportunity for significant progress in the investigation of long-term evolution of flowering plants, as part of molecular phylogenetic studies of the Tree of Life. This long-awaited fourth edition, fully revised by David Briggs, reflects new insights provided by molecular investigations and advances in computer science. Briggs considers the implications of these for our understanding of the evolution of flowering plants, as well as the potential for future advances. Numerous new sections on important topics such as the evolutionary impact of human activities, taxonomic challenges, gene flow and distribution, hybridisation, speciation and extinction, conservation and the molecular genetic basis of breeding systems will ensure that this remains a classic text for both undergraduate and graduate students in the field.

This book is divided into two parts. Part 1 deals with the evolutionary processes, describing the chromosome structure, genetic variation, multifactorial genome, polyploidy, gene duplication and speciation. Part 2 deals with the origins of agriculture and the dynamics of plant domestication, covering some cereal grains, protein plants, starchy staple and sugar crops, as well as fruit, vegetable, fibre and oil crops. A chapter on ex situ and in situ conservation of germplasm resources is included.

There are still heroes in science. They are recognized because the issues and problems they chose to study became the issues and problems of a major field of research. They are also recognized because their insights and solutions are the ones that are tested and evaluated when new ideas and technologies become available. In the field of plant evolutionary biology, the hero is George Ledyard Stebbins. His first scientific publi cation appeared in 1929 and has been followed by nearly 60 magnificent years of seminal ideas, proofs, and proposals that defined much of what was worth doing in plant biosystematics, evolution and biological conser vation. His energy, enthusiasm and good humor (widely shared at many congresses and symposia in the 'Singalongs with Stebbins') made him a wonderful teacher for both undergraduates and graduate students. He is the mentor of several generations of botanists, plant geneticists and evo lutionists. A brief biography and publication list were included in Topics in Plant Population Biology, edited by Otto T. Solbrig, Subodh Jain, George Johnson and Peter Raven (Columbia University Press, 1979) which resulted from a symposium held on the occasion of Ledyard Stebbins' 70th birthday. In this volume, population biology and physio logical ecology received major attention particularly in relation to plant form and function.

In Genes, Categories and Species, Jody Hey provides an enlightening new solution to one of biology's most ironic and perplexing puzzles. When Darwin showed that life evolves, and that it does so by natural selection, he transformed our understanding of living things. But the very question Darwin addressed-the nature of species-continues to pose an awkward conundrum for biologists. Despite enormous efforts by a great many scholars, biologists still cannot agree on how to identify species or even how to define the word "species." Genes, Categories, and Species is not like other books on the species problem, for it does not begin by asking, "What is a species?" Instead, it focuses on the very fact that biologists are stumped by species and their curious behavior in coping with that uncertainty. Faced with a persistent conundrum-and no lack of data on the subject-biologists who ponder the species problem have ceased to ask the most essential of scientific questions: "What new information do we need to resolve the problem?" This is the question that motivates this book and leads to the discoveries it reveals. The answer to the species problem lies not with the processes and patterns of biological diversity, Hey contends, but rather in the way the human mind perceives and categorizes that diversity. The promise of this book is twofold. First, it allows biologists to understand the causes of the species problem and to use this knowledge to avoid the major confusions that arise over species. Second, with its explanation of the species problem, it gives scholars and students of human nature a humbling example of how ill-suited the human mind is for certain kinds of scientific questions.

Apomixis is the consequence of a concerted mechanism that harnesses the sexual machinery and coordinates developmental steps in the ovule to produce an asexual (clonal) seed. Altered sexual developments involve widely characterized functional and anatomical changes in meiosis, gametogenesis, and embryo and endosperm formation. The ovules of apomictic plants skip meiosis and form unreduced female gametophytes whose egg cells develop into a parthenogenetic embryo, and the central cells may or may not fuse to a sperm to develop the seed endosperm. Thus, functional apomixis involves at least three components, apomeiosis, parthenogenesis, and endosperm development, modified from sexual reproduction that must be coordinated at the molecular level to progress through the developmental steps and form a clonal seed. Despite recent progress uncovering specific genes related to apomixis-like phenotypes and the formation of clonal seeds, the molecular basis and regulatory network of apomixis is still unknown. This is a central problem underlying the current limitations of apomixis breeding. This book collates twelve publications addressing different topics around the molecular basis of apomixis, illustrating recent discoveries and advances toward understanding the genetic regulation of the trait, discussing the possible origins of apomixis and the remaining challenges for its commercial deployment in plants.