Why does a Caribbean angelfish sometimes resemble its Indo-Pacific cousin, even though they have never lived in the same ocean? Why do coral reefs harbor such a wide range of stripes, spots and patterns? A study conducted by the University of Liège reveals that this explosion of color patterns is not the result of chance. The more species that make their home in a reef, the more varied the patterns, and fish from different oceans often end up looking alike, guided by the same deep biological constraints. The study is published in the journal BMC Biology.