"Species Diversity in Ecological Communities" looks at biodiversity in its broadest geographical and historical contexts. For many decades, ecologists have tended to study only small areas over short time spans in the belief that diversity is regulated by local ecological interactions. However, to understand fully how communities come to have the diversity they do and to address properly the urgent conservation problems we face, scientists must consider global patterns of species richness and the historical events that shape both regional and local communities. The authors use new theoretical developments, analyses and case studies to explore the large-scale mechanisms that generate and maintain diversity. Case studies of various regions and organisms consider how local and regional processes interact to determine patterns of species richness. The contributors emphasize the fact that ecological processes acting quickly on a local scale do not erase the effects of regional and historical events that occur more slowly and less frequently.