Coloration signals dominance in a coral reef fish

Coloration signals dominance in a coral reef fish Amundsen, Trond1, Elisabet Forsgren2, Caitlin Newport3, Sara Ostlund Nilsson1 sara.ostlundnilsson@nb.no 1Norwegian University of Science and Technology-NTNU, Høgskoleringen 5, NO7491 Trondheim 2Norwegian Institute for Nature Research - NINA P.O. Box 5685 Sluppen, NO-7485 Trondheim 3School of Biological Sciences, The University of Queensland, St Lucia, 4072, QLD Reef fishes are famous for their often extravagant coloration. Surprisingly, however, the reasons behind reef fish splendour are not well understood. In particular, there has been little focus on the roles of coloration in mate attraction and status signalling, processes that have proven central in explaining splendid colours and other ornaments in a wide range of terrestrial and freshwater organisms. We quantified orange tail coloration of a small damselfish, the sapphire devil Chrysiptera cyanea, and tested if more colourful individuals were dominant in male-male interactions. We matched pairs of males of similar size, but with markedly different degrees of tail coloration, and observed visual display interactions and aggressive encounters. Dominance tests were made both in the absence and in the presence of a female potential mate. In both tests, male tail coloration was positively associated with dominance, and dominance was linked to the ability to monopolize an artificial nest for breeding. Competition for breeding sites and territories is extreme on the reef. We suggest that one important function of extravagant reef fish coloration is to signal competitive abilities, and thus resolve intraspecific resource conflicts on the reef.