This volume is a selection of papers presented at the 25th Congress of the International Association of Theoretical and Applied Limnology (SIL). It explores the role and importance of terrestrial-aquatic ecotones in maintaining local, regional and global diversity. The 14 chapters focus on the following topics: the diversity of a wide range of biotic groups; the rationale for studying and conserving biodiversity in land/inland water ecotones; microbial biodiversity; the dynamics of diversity and its expression over gradients and boundaries; habitat complexity; ecotonal biodiversity and sustainability in unique tropical landscapes.