title: Variation in symbiont distribution between closely related coral species over large depth ranges.
abstract: Symbiotic algae in coral species distributed over a large depth range are confronted with major differences in light conditions. We studied the genetic variation of Symbiodinium in the coral genus Madracis over depth (5-40 m) and at two different colony surface positions. Using polymerase chain reaction-denaturing gradient gel electrophoresis ITS2 nuclear ribosomal DNA analyses, we consistently identified three symbiont genotypes with distributions that reveal patterns of host specificity and depth-based zonation. ITS2 type B7 Symbiodinium is the generalist type, occurring in all zooxanthellate Madracis corals and at all depths. Type B13 is restricted to the shallow water specialist Madracis mirabilis. Type B15 is typical of deep reef environments and replaces B7 in the depth generalist Madracis pharensis. Contrasting with variation over depth, we found strong functional within-colony uniformity in symbiont diversity. Relating symbiont distributions to measured physical factors (irradiance, light spectral distribution, temperature), suggests depth-based ecological function and host specificity for Symbiodinium ITS2 types, even among closely related coral species.
authors.affiliation: Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands. pfrade@nioz.nl
authors.forename: P R
authors.initials: PR
authors.lastname: Frade
authors.forename: F
authors.initials: F
authors.lastname: De Jongh
authors.forename: F
authors.initials: F
authors.lastname: Vermeulen
authors.forename: J
authors.initials: J
authors.lastname: van Bleijswijk
authors.forename: R P M
authors.initials: RP
authors.lastname: Bak
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000254:growth & development*; D001483:Base Sequence; D002140:California; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D056890:Eukaryota / Q000145:classification / Q000235:genetics* / Q000254:growth & development*; D014644:Genetic Variation; D005843:Geography; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D013559:Symbiosis
chemical_list: D004275:DNA, Ribosomal