title: Cohabitation promotes high diversity of clownfishes in the Coral Triangle.
abstract: Global marine biodiversity peaks within the Coral Triangle, and understanding how such high diversity is maintained is a central question in marine ecology. We investigated broad-scale patterns in the diversity of clownfishes and their host sea anemones by conducting 981 belt-transects at 20 locations throughout the Indo-Pacific. Of the 1508 clownfishes encountered, 377 fish occurred in interspecific cohabiting groups and cohabitation was almost entirely restricted to the Coral Triangle. Neither the diversity nor density of host anemone or clownfish species alone influenced rates of interspecific cohabitation. Rather cohabitation occurred in areas where the number of clownfish species exceeds the number of host anemone species. In the Coral Triangle, cohabiting individuals were observed to finely partition their host anemone, with the subordinate species inhabiting the periphery. Furthermore, aggression did not increase in interspecific cohabiting groups, instead dominant species were accepting of subordinate species. Various combinations of clownfish species were observed cohabiting (independent of body size, phylogenetic relatedness, evolutionary age, dentition, level of specialization) in a range of anemone species, thereby ensuring that each clownfish species had dominant reproductive individuals in some cohabiting groups. Clownfishes are obligate commensals, thus cohabitation is an important process in maintaining biodiversity in high diversity systems because it supports the persistence of many species when host availability is limiting. Cohabitation is a likely explanation for high species richness in other obligate commensals within the Coral Triangle, and highlights the importance of protecting these habitats in order to conserve unique marine biodiversity.
authors.affiliation: Coral Reef Research Unit, School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK Plant Functional Biology and Climate Change Cluster, University of Technology Sydney, Broadway, NSW 2007, Australia emma.camp@uts.edu.au.
authors.forename: Emma F
authors.identifier: http://orcid.org/0000-0003-1962-1336
authors.initials: EF
authors.lastname: Camp
authors.affiliation: Department of Environment and Agriculture, Curtin, University, PO Box U1987, Perth, Western Australia 6845, Australia.
authors.forename: Jean-Paul A
authors.identifier: http://orcid.org/0000-0003-0331-354X
authors.initials: JP
authors.lastname: Hobbs
authors.affiliation: Department of Environment and Agriculture, Curtin, University, PO Box U1987, Perth, Western Australia 6845, Australia.
authors.forename: Maarten
authors.initials: M
authors.lastname: De Brauwer
authors.affiliation: Coral Reef Research Unit, School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Dumbrell
authors.affiliation: Coral Reef Research Unit, School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Smith
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D049628:Body Size; D057894:Coral Reefs; D019156:Indian Ocean; D010140:Pacific Ocean; D010473:Perciformes / Q000502:physiology*; D010802:Phylogeny; D011156:Population Density; D012615:Sea Anemones / Q000502:physiology*; D013559:Symbiosis
keywords: amphiprion; anemonefish; biodiversity; coral reefs; mutualism; symbiosis