Why do larger areas have more species? What makes diversity so high near the equator? Has the number of species grown during the past 600 million years? Does habitat diversity support species diversity, or is it the other way around? What reduces diversity in ecologically productive places? At what scales of space and time do diversity patterns hold? Do the mechanisms that produce them vary with scale? This book examines these questions and many others, by employing both theory and data in the search for answers. Surprisingly, many of the questions have reasonably likely answers. By identifying these, attention can be turned toward life’s many, still-unexplained diversity patterns. As evolutionary ecologists race to understand biodiversity before it is too late, this book will help set the agenda for diversity research into the next century.