Hamlets are a group of colourful coral reef fish found throughout the Caribbean. Ten species of hamlet have been discovered and each can be easily recognized by its own distinct colour pattern. In some areas, as many as seven varieties can be found on a single reef. However, most hamlet species are only found at specific locations. The blue hamlet, for example, is found only in the Florida region. How these very different looking, yet very closely related species came to be has been a a subject of debate among scientists. Data collected by divers and snorkelers as part of the REEF Volunteer Fish Survey Project were used in a large analysis to better understand the patterns of evolution in these and other marine fishes. They found that even widespread hamlet species are not found everywhere, and identified high density hotspots for each species. Because different species hotspots overlap and many species have more than one hotspot, the results do not support the theory that hamlets originated independently when they were geographically separated in the past. The research also showed how ecological factors, such as competition for food or habitat, may influence how different hamlet species co-exist. To contact the lead author - bholt@bio.ku.dk