The section "Special Features" is dedicated to share with its readers thematic works about natural history, ecology and evolution. In this introduction we focus on the role that theories play in the construction of evolutionary thinking. First, we briefly show the importance of Lamarck's work in the context of pre-Darwinian theories about organic evolution. Then, the main components of the Darwinian theoretical core and its postDarwinian extensions are thoroughly discussed. Finally the essays following this introduction in the present issue are summarized.