The fish assemblages of the Great Barrier Reef: their diversity and origin

[Extract] There are three critical features of coral reef fish faunas. First, they represent the most diverse assemblages of vertebrates on the planet. Second, this diversity may be seen at very local scales: hundreds of species co-occur within relatively small areas. Third, most species have broad geographical distributions. Thus, the observer moving across a small area of reef will encounter many different species of fish. Moving over relatively small areas (500 m2) of reef habitat can reveal up to 100 species of reef fishes: far more vertebrates than would be encountered in any terrestrial habitat. If the scale of observation is increased to cover geographically distant reefs within the same ocean basin similar diversities may be encountered and in many instances the same species will be observed. However, species diversity and species identity do vary on geographic scales in ways that reflect the location and the evolutionary history of the reef habitat. In order to understand the processes that underlie this incredible diversity of fishes, we must also appreciate the forces that have modified the reef habitat over time