title: Species boundaries and phylogenetic relationships between Atlanto-Mediterranean shallow-water and deep-sea coral associated Hexadella species (Porifera, Ianthellidae).
abstract: Coral reefs constitute the most diverse ecosystem of the marine realm and an increasing number of studies are focusing on coral species boundaries, distribution, and on processes that control species ranges. However, less attention has been paid to coral associated species. Deep-sea sponges dominate cold-water coral ecosystems, but virtually nothing is known about their molecular diversity. Moreover, species boundaries based on morphology may sometimes be inadequate, since sponges have few diagnostic characters. In this study, we investigated the molecular diversity within the genus Hexadella (Porifera, Demospongiae, Verongida, Ianthellidae) from the European shallow-water environment to the deep-sea coral ecosystems. Three molecular markers were used: one mitochondrial (COI) and two nuclear gene fragments (28S rDNA and the ATPS intron). Phylogenetic analyses revealed deeply divergent deep-sea clades congruent across the mitochondrial and nuclear markers. One clade contained specimens from the Irish, the Scottish, and the Norwegian margins and the Greenland Sea (Hexadella dedritifera) while another clade contained specimens from the Ionian Sea, the Bay of Biscay, and the Irish margin (H. cf. dedritifera). Moreover, these deeply divergent deep-sea clades showed a wide distribution suggesting a connection between the reefs. The results also point to the existence of a new deep-sea species (Hexadella sp.) in the Mediterranean Sea and of a cryptic shallow-water species (Hexadella cf. pruvoti) in the Gorringe Bank. In contrast, low genetic differentiation between H. cf. dedritifera and H. pruvoti from the Mediterranean Sea was observed. All Hexadella racovitzai specimens from the Mediterranean Sea (shallow and deep) to the Atlantic formed a monophyletic group.
authors.affiliation: Biology Department, Ghent University, Ghent, Belgium. julie.reveillaud@ugent.be
authors.forename: Julie
authors.initials: J
authors.lastname: Reveillaud
authors.forename: Thomas
authors.initials: T
authors.lastname: Remerie
authors.forename: Rob
authors.initials: R
authors.lastname: van Soest
authors.forename: Dirk
authors.initials: D
authors.lastname: Erpenbeck
authors.forename: Paco
authors.initials: P
authors.lastname: Cárdenas
authors.forename: Sofie
authors.initials: S
authors.lastname: Derycke
authors.forename: Joana R
authors.initials: JR
authors.lastname: Xavier
authors.forename: Annelien
authors.initials: A
authors.lastname: Rigaux
authors.forename: Ann
authors.initials: A
authors.lastname: Vanreusel
mesh_terms: D000818:Animals; D037421:Anthozoa; D001267:Atlantic Ocean; D001499:Bayes Theorem; D002467:Cell Nucleus / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D019143:Evolution, Molecular; D014644:Genetic Variation; D008522:Mediterranean Sea; D010802:Phylogeny; D011161:Porifera / Q000145:classification / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial