title: Body shape transformation along a shared axis of anatomical evolution in labyrinth fishes (Anabantoidei).
abstract: Major morphological transformations, such as the evolution of elongate body shape in vertebrates, punctuate evolutionary history. A fundamental step in understanding the processes that give rise to such transformations is identification of the underlying anatomical changes. But as we demonstrate in this study, important insights can also be gained by comparing these changes to those that occur in ancestral and closely related lineages. In labyrinth fishes (Anabantoidei), rapid evolution of a highly derived torpedo-shaped body in the common ancestor of the pikehead (Luciocephalus aura and L. pulcher) occurred primarily through exceptional elongation of the head, with secondary contributions involving reduction in body depth and lengthening of the precaudal vertebral region. This combination of changes aligns closely with the primary axis of anatomical diversification in other anabantoids, revealing that pikehead evolution involved extraordinarily rapid change in structures that were ancestrally labile. Finer-scale examination of the anatomical components that determine head elongation also shows alignment between the pikehead evolutionary trajectory and the primary axis of cranial diversification in anabantoids, with much higher evolutionary rates leading to the pikehead. Altogether, our results show major morphological transformation stemming from extreme change along a shared morphological axis in labyrinth fishes.
authors.affiliation: Department of Organismal and Environmental Biology, Christopher Newport University, Newport News, Virginia, 23606. david.collar@cnu.edu.
authors.forename: David C
authors.initials: DC
authors.lastname: Collar
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California, 95060.
authors.forename: Michelle
authors.initials: M
authors.lastname: Quintero
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California, 95060.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Buttler
authors.affiliation: Department of Biology, Adelphi University, Garden City, New York, 11530.
authors.forename: Andrea B
authors.initials: AB
authors.lastname: Ward
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, California, 95060.
authors.forename: Rita S
authors.initials: RS
authors.lastname: Mehta
mesh_terms: D000818:Animals; D005075:Biological Evolution; D006257:Head / Q000033:anatomy & histology; D010473:Perciformes / Q000033:anatomy & histology* / Q000145:classification / Q000235:genetics*; D010802:Phylogeny
keywords: Axial skeleton; Luciocephalus; elongation; gourami; pikehead; rate of evolution