We have come a long way towards better understanding how new species originate, i.e. speciation, which long remained Darwin's "mystery of mysteries." Since speciation is the underlying mechanism for radiations, it is the ultimate causation for the biological diversity of life that surrounds us. Without a doubt, Charles Darwin's contribution to our understanding of the origin of biodiversity cannot be overestimated. This book is a contribution to both the Darwin Year we celebrated in 2009 and to the Year of Biodiversity and Conservation 2010. The studies and model cases presented show the progress and dynamics of research based on Darwinian theories and sheds light on its implications in the context of current biodiversity crises. The great importance of adaptive (and non-adaptive) radiations for biodiversity is widely accepted, but our understanding of the processes and mechanisms involved is still limited and generalizations need to be based on the accumulation of more evidence from additional case studies. The studies presented in this volume are those urgently needed and focus on a variety of organisms and different aspects of radiations. The scientific results presented therein are excellent examples not only of evolution in action, but also of active research on evolutionary processes and their most apparent outcome -- biodiversity.

Radiations, or Evolution in Action We have just celebrated the "Darwin Year" with the double anniversary of his 200th birthday and 150th year of his masterpiece, "On the Origin of Species by means of Natural Selection". In this work, Darwin established the factual evidence of biological evolution, that species change over time, and that new organisms arise by the splitting of ancestral forms into two or more descendant species. However, above all, Darwin provided the mechanisms by arguing convincingly that it is by natural selection - as well as by sexual selection (as he later added) - that organisms adapt to their environment. The many discoveries since then have essentially con?rmed and strengthened Darwin's central theses, with latest evidence, for example, from molecular genetics, revealing the evolutionary relationships of all life forms through one shared history of descent from a common ancestor. We have also come a long way to progressively understand more on how new species actually originate, i. e. on speciation which remained Darwin's "mystery of m- teries", as noted in one of his earliest transmutation notebooks. Since speciation is the underlying mechanism for radiations, it is the ultimate causation for the biological diversity of life that surrounds us.