title: Interspecific variation of calls in clownfishes: degree of similarity in closely related species.
abstract: BACKGROUND
  Clownfishes are colorful coral reef fishes living in groups in association with sea anemones throughout the Indo-Pacific Ocean. Within their small societies, size hierarchy determines which fish have access to reproduction. These fishes are also prolific callers whose aggressive sounds seem to play an important role in the social hierarchy. Agonistic interactions being involved in daily behaviour suggest how acoustic communication might play an important role in clownfish group. Sounds were recorded and compared in fourteen clownfish species (some of which have never been recorded before) to evaluate the potential role of acoustic communication as an evolutionary driving force.
  
  
  RESULTS
  Surprisingly, the relationship between fish size and both dominant frequency and pulse duration is not only species-specific; all the specimens of the 14 species are situated on exactly the same slope, which means the size of any Amphiprion can be predicted by both acoustic features. The number of pulses broadly overlaps among species, whereas the pulse period displays the most variation even if it shows overlap among sympatric species. Sound comparisons between three species (A. akallopisos, A. ocellaris and A. frenatus) having different types of teeth and body shape do not show differences neither in the acoustic waveform nor in the power spectrum.
  
  
  CONCLUSIONS
  Significant overlap in acoustic features demonstrates that the sound-producing mechanism is highly conservative among species. Differences in the calls of some species are due to size dimorphism and the sound variation might be in this case a by-product. This morphological constraint does not permit a consideration of acoustic communication as the main driving force in the diversification of clownfishes. Moreover, calls are not produced to find mate and consequently are less subject to variations due to partner preference, which restricts the constraints of diversification. Calls are produced to reach and defend the competition to mate access. However, differences in the pulse period between cohabiting species show that, in some case, sounds can help to differentiate the species, to prevent competition between cohabiting species and to promote the diversification of taxa.
authors.affiliation: Laboratoire de Morphologie Fonctionnelle et Evolutive, Université de Liège, Allée de la Chimie 3, 4000 Liège, Belgium.
authors.forename: Orphal
authors.initials: O
authors.lastname: Colleye
authors.forename: Pierre
authors.initials: P
authors.lastname: Vandewalle
authors.forename: Déborah
authors.initials: D
authors.lastname: Lanterbecq
authors.forename: David
authors.initials: D
authors.lastname: Lecchini
authors.forename: Eric
authors.initials: E
authors.lastname: Parmentier
mesh_terms: D000162:Acoustics; D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D010473:Perciformes / Q000033:anatomy & histology / Q000502:physiology*; D013045:Species Specificity; D014828:Vocalization, Animal