title: Molecular phylogeny, systematics and morphological evolution of the acorn barnacles (Thoracica: Sessilia: Balanomorpha).
abstract: The Balanomorpha are the largest group of barnacles and rank among the most diverse, commonly encountered and ecologically important marine crustaceans in the world. Paradoxically, despite their relevance and extensive study for over 150years, their evolutionary relationships are still unresolved. Classical morphological systematics was often based on non-cladistic approaches, while modern phylogenetic studies suffer from severe undersampling of taxa and characters (both molecular and morphological). Here we present a phylogenetic analysis of the familial relationships within the Balanomorpha. We estimate divergence times and examine morphological diversity based on five genes, 156 specimens, 10 fossil calibrations, and six key morphological characters. Two balanomorphan superfamilies, eight families and twelve genera were identified as polyphyletic. Chthamaloids, chionelasmatoid and pachylasmatoids split first from the pedunculated ancestors followed by a clade of tetraclitoids and coronuloids, and most of the balanoids. The Balanomorpha split from the Verrucidae (outgroup) in the Lower Cretaceous (139.6 Mya) with all the main lineages, except Pachylasmatoidea, having emerged by the Paleocene (60.9 Mya). Various degrees of convergence were observed in all the assessed morphological characters except the maxillipeds, which suggests that classical interpretations of balanomorphan morphological evolution need to be revised and reinterpreted.
authors.affiliation: CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Rua Padre Armando Quintas 7, Universidade do Porto, Campus Agrário de Vairão, Vairão 4485-661, Portugal; Computational Biology Institute, George Washington University, Ashburn, VA 20147, USA; Department of Invertebrate Zoology, US National Museum of Natural History, Smithsonian Institution, Washington, DC 20013, USA. Electronic address: mlosada323@gmail.com.
authors.forename: Marcos
authors.initials: M
authors.lastname: Pérez-Losada
authors.affiliation: Marine Biology Section, Department of Biology, University of Copenhagen, Universitetsparken 4, DK-2100 Copenhagen, Denmark.
authors.forename: Jens T
authors.initials: JT
authors.lastname: Høeg
authors.affiliation: The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, 52900 Ramat Gan, Israel.
authors.forename: Noa
authors.initials: N
authors.lastname: Simon-Blecher
authors.affiliation: The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, 52900 Ramat Gan, Israel.
authors.forename: Yair
authors.initials: Y
authors.lastname: Achituv
authors.affiliation: Perth Museums & Collections Western Australian Museum, 49 Kew Street, Welshpool, Western Australia 6106, Australia.
authors.forename: Diana
authors.initials: D
authors.lastname: Jones
authors.affiliation: Computational Biology Institute, George Washington University, Ashburn, VA 20147, USA; Department of Invertebrate Zoology, US National Museum of Natural History, Smithsonian Institution, Washington, DC 20013, USA.
authors.forename: Keith A
authors.initials: KA
authors.lastname: Crandall
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D005580:Fossils; D008957:Models, Genetic; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D001468:Thoracica / Q000033:anatomy & histology / Q000145:classification*
keywords: Balanomorpha; Barnacle; DNA; Morphology; Phylogeny; Systematics