The highly popular species in the ocellaris group are, along with the biaculeatus group, part of the basalmost lineage in Amphiprion. In this treatment of the group, I have chosen to refer to these with the common name “clownfish”, but the distinction between this term and “anemonefish” is absent in most other sources. The name “clown anemonefish” is also in use, but lends little clarity. The different usage seems to be somewhat regional, with Australians and Europeans favoring “anemonefish” while North America and Asia leans more towards “clownfish”. Frankly, I fail to see what is so clown-like about these fishes…
Unlike most other groups in the genus, these fishes have been relatively well-studied, with a thorough population genetics study published by Timms et al 2008. In that study, cryptic species were discovered but not described. These correspond to some familiar ecoregions, such as the unique population of A. ocellaris found in the Eastern Indian Ocean, but also include a population of A. percula in parts of Northeastern Indonesia that differ considerably from those found to the east in the Bismarck Archipelago. Other possible species may include the well-known melanistic population form Northern Australia and perhaps those from the Great Barrier Reef.
Ecologically, these fishes are often found in shallow lagoons and reef flats and seem to be outcompeted by the skunk anemonefishes of the perideraion group when habitat is limiting. Both groups specialize in the Magnificent Sea Anemone (Heteractis magnifica), but the ocellaris clownfishes are also able to make use of Stichodactyla carpet anemones.
Amphiprionology 