title: Trait decoupling promotes evolutionary diversification of the trophic and acoustic system of damselfishes.
abstract: Trait decoupling, wherein evolutionary release of constraints permits specialization of formerly integrated structures, represents a major conceptual framework for interpreting patterns of organismal diversity. However, few empirical tests of this hypothesis exist. A central prediction, that the tempo of morphological evolution and ecological diversification should increase following decoupling events, remains inadequately tested. In damselfishes (Pomacentridae), a ceratomandibular ligament links the hyoid bar and lower jaws, coupling two main morphofunctional units directly involved in both feeding and sound production. Here, we test the decoupling hypothesis by examining the evolutionary consequences of the loss of the ceratomandibular ligament in multiple damselfish lineages. As predicted, we find that rates of morphological evolution of trophic structures increased following the loss of the ligament. However, this increase in evolutionary rate is not associated with an increase in trophic breadth, but rather with morphofunctional specialization for the capture of zooplanktonic prey. Lineages lacking the ceratomandibular ligament also shows different acoustic signals (i.e. higher variation of pulse periods) from others, resulting in an increase of the acoustic diversity across the family. Our results support the idea that trait decoupling can increase morphological and behavioural diversity through increased specialization rather than the generation of novel ecotypes.
authors.affiliation: Laboratoire de Morphologie Fonctionnelle et Evolutive, Applied and Fundamental Fish Research Center, Université de Liège, 4000 Liège, Belgium bruno.frederich@ulg.ac.be.
authors.forename: Bruno
authors.initials: B
authors.lastname: Frédérich
authors.affiliation: Laboratoire de Morphologie Fonctionnelle et Evolutive, Applied and Fundamental Fish Research Center, Université de Liège, 4000 Liège, Belgium.
authors.forename: Damien
authors.initials: D
authors.lastname: Olivier
authors.affiliation: Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland Swiss Institute of Bioinformatics, Génopode, Quartier Sorge, 1015 Lausanne, Switzerland.
authors.forename: Glenn
authors.initials: G
authors.lastname: Litsios
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Alfaro
authors.affiliation: Laboratoire de Morphologie Fonctionnelle et Evolutive, Applied and Fundamental Fish Research Center, Université de Liège, 4000 Liège, Belgium.
authors.forename: Eric
authors.initials: E
authors.lastname: Parmentier
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D020387:Food Chain; D020412:Multifactorial Inheritance; D010473:Perciformes / Q000033:anatomy & histology / Q000502:physiology*; D010802:Phylogeny; D014828:Vocalization, Animal
keywords: constraint; coral reef fishes; morphological novelty; morphospace; sound production; trait evolution