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FRIMEDBIO-Fri prosj.st. med.,helse,biol

Coral Reef Fish Coloration: Sexual Selection, Diversity and Speciation [revised Jan. 09]

Awarded: NOK 6.6 mill.

Tropical coral reefs are among the environments most threatened by human impacts in the World today. At same time, coral reefs are the "rainforests of the oceans", with an extremely high biodiversity. Only a minority of the organisms inhabiting coral reefs have been subject to study; for most, no scientific knowledge exists. The CoralFish project has aimed to contribute to understand why reef fishes have such splendid colours. Our research has taken place at Lizard Island Research Station on the Great Barrier Reef in Australia. The primary research focus has been to investigate the role of extravagant coloration in competition over territories and mates, and in mate choice. We have explored these issues adopting a combination of systematic field observations and controlled laboratory experiments, using two species of damselfishes as our model organisms. The results suggest that splendid colours are of importance both in male and female mate choice, and also in conflict resolution within the sexes. On the reef, one of the damselfishes studied lives in small colonies of varying size. Based on systematic field observations, we have investigated how social structuring (number of males in a colony) affects competitive dynamics and mate choice. We have also studied the dynamics of coloration in the same species, and found a change from splendid blue "show-off colours" while free-swimming to an almost black colour when hiding in the nest. This colour change happens within seconds and is faster than documented in any other fish species. Taken together, our results show that the splendid colours of the studied reef fishes play important roles both in competition and mate choice, suggesting that such functions of colour may be important in reef fishes. The project is the most comprehensive study of sexual selection in reef fishes to date, and has provided novel and original insights into the dynamics of a highly important yet threatened marine ecosystem.

Tropical coral reefs are the most diverse and complex marine habitats on earth. No other environment is host to so many fish species, with such a diversity of strikingly beautiful colours and patterns. At the same time, biological knowledge about most cor al reef fishes is scant. This is unfortunate, especially in light of the fact that 60% of the World's coral reefs are at risk from human activity. We currently do not understand (a) why there are so many species, often similar in body form but differing i n coloration, nor (b) why coral reef fishes are typically so colourful. Traditionally, the view has been that reef fish colours are selected mainly for species recognition. However, the evidence to support this hypothesis is limited, and it does not expla in species diversity. By contrast, the hypothesis that colours are sexually selected, extensively supported in other animal groups, has largely been neglected for coral reef fishes. Unlike species recognition and other hypotheses proposed, sexual selectio n can potentially explain not only why many species are colourful, but also why there are so many species. This is because strong sexual selection can lead to rapid sympatric speciation through character divergence and reproductive isolation. Our project will test these ideas, by integrating field studies, laboratory experiments, and comparative analyses. The project integrates Norwegian expertise in behavioural ecology of marine fishes, Australian expertise in reef fish ecology and physiology, and Britis h expertise in comparative analyses and biodiversity. Field and lab work will be conducted at Lizard Island Research Station, Australia, using the black-and-gold chromis Neoglyphidodon nigroris as a model species. Comparative work will be based on data co llected by team-members and on published data, covering several reef fish taxa, and will have its base at Imperial College, UK. The project will recruit a post-doc to Norwegian evolutionary and behavioural ecology.

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FRIMEDBIO-Fri prosj.st. med.,helse,biol

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