title: The origins and evolution of dwarf males and habitat use in thoracican barnacles.
abstract: Barnacles are exceptional in having various sexual systems (androdioecy, hermaphroditism, dioecy) and with a high morphological diversity of males, though these are always minute (dwarf) compared to their female or hermaphrodite partners. For the first time, we use a multiple DNA marker-based phylogeny to elucidate the ancestral states and evolution of (1) dwarf males, (2) their morphology when present, (3) their attachment site on the partner, and (4) habitat use in thoracican barnacles. Our taxon sampling was especially rich in rare deep-sea Scalpelliformes and comprised species with diverse sexual systems and dwarf male morphologies. Within the thoracican barnacles dwarf male evolution is subject to extensive convergence, but always correlated to similar ecological conditions. Males evolved convergently at least four times from purely hermaphroditic ancestors, in each case correlated with the invasion into habitats with low mating group sizes. The independent evolution of dwarf males in these lineages dovetails with the males having different morphologies and occurring in several different locations on their sexual partner.
authors.affiliation: Department of Marine Biotechnology and Resources, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan; Biodiversity Research Center, Academia Sinica, Nankang, Taipei, Taiwan. Electronic address: hsiuchinlin@mail.nsysu.edu.tw.
authors.forename: Hsiu-Chin
authors.initials: HC
authors.lastname: Lin
authors.affiliation: Section of Marine Biology, Department of Biology, University of Copenhagen, Universitetsparken 4, Copenhagen 2100, Denmark. Electronic address: jthoeg@bio.ku.dk.
authors.forename: Jens T
authors.initials: JT
authors.lastname: Høeg
authors.affiliation: Faculty of Science, Nara Women's University, Kitauoya-nishi, Nara 630-8506, Japan. Electronic address: yusa@cc.nara-wu.ac.jp.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Yusa
authors.affiliation: Biodiversity Research Center, Academia Sinica, Nankang, Taipei, Taiwan. Electronic address: chankk@gate.sinica.edu.tw.
authors.forename: Benny K K
authors.initials: BK
authors.lastname: Chan
mesh_terms: D000818:Animals; D005075:Biological Evolution; D012734:Disorders of Sex Development; D017753:Ecosystem; D005260:Female; D008297:Male; D010802:Phylogeny; D012098:Reproduction / Q000235:genetics; D001468:Thoracica / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics / Q000502:physiology*
keywords: Androdioecy; Deep-sea; Dwarf male; Morphological diversity; Scalpellidae; Sexual system