In a new study published in the journal Science Advances, an international research team led by the Leibniz Centre for Tropical Marine Research (ZMT) challenges traditional ideas about how new animal species form. The study focuses on hamlets – colourful reef fishes from the Caribbean. In addition to ZMT, scientists from the University of Oldenburg, the Senckenberg Research Institute and Natural History Museum Frankfurt and the Smithsonian Tropical Research Institute (STRI) in Panama were involved in the study. Researchers from Colombia, Mexico, the USA and the UK also contributed to the publication.