title: Functional coupling constrains craniofacial diversification in Lake Tanganyika cichlids.
abstract: Functional coupling, where a single morphological trait performs multiple functions, is a universal feature of organismal design. Theory suggests that functional coupling may constrain the rate of phenotypic evolution, yet empirical tests of this hypothesis are rare. In fish, the evolutionary transition from guarding the eggs on a sandy/rocky substrate (i.e. substrate guarding) to mouthbrooding introduces a novel function to the craniofacial system and offers an ideal opportunity to test the functional coupling hypothesis. Using a combination of geometric morphometrics and a recently developed phylogenetic comparative method, we found that head morphology evolution was 43% faster in substrate guarding species than in mouthbrooding species. Furthermore, for species in which females were solely responsible for mouthbrooding the males had a higher rate of head morphology evolution than in those with bi-parental mouthbrooding. Our results support the hypothesis that adaptations resulting in functional coupling constrain phenotypic evolution.
authors.affiliation: Evolutionary Biology Centre, Department of Ecology and Genetics/Animal Ecology, Uppsala University, Norbyvägen 18D, 75236 Uppsala, Sweden masahito.tsuboi@ebc.uu.se.
authors.forename: Masahito
authors.identifier: http://orcid.org/0000-0002-0144-2893
authors.initials: M
authors.lastname: Tsuboi
authors.affiliation: Laboratorio de Conducta Animal, Instituto de Ecología, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, UNAM, D.F. 04510, México Department of Zoology/Ethology, Stockholm University, Svante Arrhenius väg 18B, 10691 Stockholm, Sweden.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Gonzalez-Voyer
authors.affiliation: Department of Zoology/Ethology, Stockholm University, Svante Arrhenius väg 18B, 10691 Stockholm, Sweden.
authors.forename: Niclas
authors.initials: N
authors.lastname: Kolm
mesh_terms: D000220:Adaptation, Biological; D000351:Africa, Eastern; D000818:Animals; D005075:Biological Evolution; D023681:Cichlids / Q000033:anatomy & histology*; D005260:Female; D060106:Lakes; D008297:Male; D010802:Phylogeny; D012886:Skull / Q000033:anatomy & histology
keywords: constraints; functional coupling; geometric morphometrics; phylogenetic comparative analysis; rate of evolution