title: Adaptive radiation of chemosymbiotic deep-sea mussels.
abstract: Adaptive radiations present fascinating opportunities for studying the evolutionary process. Most cases come from isolated lakes or islands, where unoccupied ecological space is filled through novel adaptations. Here, we describe an unusual example of an adaptive radiation: symbiotic mussels that colonized island-like chemosynthetic environments such as hydrothermal vents, cold seeps and sunken organic substrates on the vast deep-sea floor. Our time-calibrated molecular phylogeny suggests that the group originated and acquired sulfur-oxidizing symbionts in the Late Cretaceous, possibly while inhabiting organic substrates and long before its major radiation in the Middle Eocene to Early Oligocene. The first appearance of intracellular and methanotrophic symbionts was detected only after this major radiation. Thus, contrary to expectations, the major radiation may have not been triggered by the evolution of novel types of symbioses. We hypothesize that environmental factors, such as increased habitat availability and/or increased dispersal capabilities, sparked the radiation. Intracellular and methanotrophic symbionts were acquired in several independent lineages and marked the onset of a second wave of diversification at vents and seeps. Changes in habitat type resulted in adaptive trends in shell lengths (related to the availability of space and energy, and physiological trade-offs) and in the successive colonization of greater water depths.
authors.affiliation: Marine Ecosystems Research Department, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), , 2-15 Natsushima, Yokosuka 237-0061, Japan, Geoscience Center, Geobiology Group, University of Göttingen, , Goldschmidtstrasse 3, Göttingen 37077, Germany, Department of Biology, Pennsylvania State University, , University Park, PA 16802, USA, School of Biological Sciences, University of Sydney, , Sydney, New South Wales 2006, Australia, Museum of New Zealand Te Papa Tongarewa, , PO Box 467, 169 Tory St., Te Aro, Wellington 6011, New Zealand, Faculty of Education and Human Sciences, University of Yamanashi, , Kofu, Yamanashi 400-8510, Japan.
authors.forename: Julien
authors.initials: J
authors.lastname: Lorion
authors.forename: Steffen
authors.initials: S
authors.lastname: Kiel
authors.forename: Baptiste
authors.initials: B
authors.lastname: Faure
authors.forename: Masaru
authors.initials: M
authors.lastname: Kawato
authors.forename: Simon Y W
authors.initials: SY
authors.lastname: Ho
authors.forename: Bruce
authors.initials: B
authors.lastname: Marshall
authors.forename: Shinji
authors.initials: S
authors.lastname: Tsuchida
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Miyazaki
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Fujiwara
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D002467:Cell Nucleus / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism; D017753:Ecosystem; D019143:Evolution, Molecular; D049810:Genetic Speciation; D008969:Molecular Sequence Data; D049879:Mytilidae / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D004272:DNA, Mitochondrial
keywords: adaptive radiation; cold seep; hydrothermal vent; organic falls; phylogenetics; symbiosis
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